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<document id="C13283DE3365727710AA293440688C25" ID-CLB-Dataset="306258" ID-DOI="10.1093/zoolinnean/zlad188" ID-GBIF-Dataset="b8ca0967-bd1c-4be7-a364-da2db5468f38" ID-ISSN="0024-4082" ID-Zenodo-Dep="14333139" IM.bibliography_approvedBy="felipe" IM.illustrations_approvedBy="juliana" IM.materialsCitations_approvedBy="juliana" IM.metadata_approvedBy="juliana" IM.taxonomicNames_approvedBy="juliana" IM.treatments_approvedBy="juliana" checkinTime="1732845143881" checkinUser="plazi" docAuthor="Santos, Rodolfo Otávio, Wilkinson, Mark, Ribeiro, do Couto Graziela, Carvalho, Alberto B. &amp; Zaher, Hussam" docDate="2024" docId="03CD9542FFAFFFFCECA73064D155FA1F" docLanguage="en" docName="zlad188.pdf" docOrigin="Zoological Journal of the Linnean Society 202 (2)" docSource="https://doi.org/10.1093/zoolinnean/zlad188" docStyle="DocumentStyle:4F230B9370E98E256D973D6DFB57F36C.9:ZoolJLinnSoc.2023-.journal_article" docStyleId="4F230B9370E98E256D973D6DFB57F36C" docStyleName="ZoolJLinnSoc.2023-.journal_article" docStyleVersion="9" docTitle="Ymboirana acrux Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher 2024, sp.nov." docType="treatment" docVersion="3" lastPageNumber="20" masterDocId="FFF4ED3AFFADFFEFEF583629D421FFB3" masterDocTitle="The first fossil record of an aquatic caecilian (Gymnophiona: Typhlonectidae)" masterLastPageNumber="23" masterPageNumber="1" pageNumber="3" updateTime="1733748216497" updateUser="ExternalLinkService">
<mods:mods id="25EE269AD72155FA92671EB96B612F48" xmlns:mods="http://www.loc.gov/mods/v3">
<mods:titleInfo id="440CE22841B46FEEC0222B25A1D50690">
<mods:title id="B62AB5A8A46C43864B49AEBB77D57CA6">The first fossil record of an aquatic caecilian (Gymnophiona: Typhlonectidae)</mods:title>
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<mods:name id="CE453D72555A26F35B35939AD4A3898F" type="personal">
<mods:role id="D7F6E6D42B4C146D161B31E29BBEFE52">
<mods:roleTerm id="782314B59DFB2C3955286568782CA0E4">Author</mods:roleTerm>
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<mods:namePart id="535177FA30C02A51D58623FA39D6942C">Santos, Rodolfo Otávio</mods:namePart>
<mods:affiliation id="5F0598D47B3FF6A7E763017196107033">Instituto de Biociências, Universidade de São Paulo, Rua do Matão, Tv. 14, 05508 * 090, São Paulo, SP, Brazil</mods:affiliation>
<mods:nameIdentifier id="A5D8505A58C6A338F32BB51665A91ED0" type="email">rodolfosantos013@gmail.com</mods:nameIdentifier>
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<mods:namePart id="3E3E50B7C7BE3DDED321D505A47B45D3">Wilkinson, Mark</mods:namePart>
<mods:affiliation id="529721CB82791CF2D2E2B4B9A68F96E5">Herpetology Lab, The Natural History Museum, Cromwell Rd, South Kensington, SW 7 5 BD, London, UK</mods:affiliation>
</mods:name>
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<mods:role id="5F4609FC853F7743748EA100B4AB13DB">
<mods:roleTerm id="ED3B297AE81E4E9C81119A97F7E553E6">Author</mods:roleTerm>
</mods:role>
<mods:namePart id="78C7992F0F5D44B8F6E87AFDB81D28B7">Ribeiro, do Couto Graziela</mods:namePart>
<mods:affiliation id="6E62012F7F3711E7654BAC319EB0305E">Museu de História Natural de Taubaté Doutor Herculano Alvarenga, Rua Juvenal Dias de Carvalho, Jardim do Sol, 12070 * 640, Taubaté, SP, Brazil</mods:affiliation>
</mods:name>
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<mods:role id="E52FB7DC3D8E23D99728CAB65589AFA0">
<mods:roleTerm id="F52958E91C7C34007F3AB3088410818B">Author</mods:roleTerm>
</mods:role>
<mods:namePart id="CF02D4B7E796A6B3140467F2288549F9">Carvalho, Alberto B.</mods:namePart>
<mods:affiliation id="515C16C3B4DB5EB366AB901219EDDA44">Serviço de Vertebrados, Museu de Zoologia da Universidade de São Paulo, Avenida Nazaré 481, 04263 * 000, São Paulo, SP, Brazil</mods:affiliation>
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<mods:roleTerm id="A21FE7856478DC069C8DDB36865D8FA5">Author</mods:roleTerm>
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<mods:namePart id="5A03D45FE87745D61E70987DC5658C12">Zaher, Hussam</mods:namePart>
<mods:affiliation id="598CF16F63A6F1E8DC2A27B97060FEFF">Serviço de Vertebrados, Museu de Zoologia da Universidade de São Paulo, Avenida Nazaré 481, 04263 * 000, São Paulo, SP, Brazil</mods:affiliation>
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<mods:title id="A08084084FFF2B5C1ABAE6358AFD3B25">Zoological Journal of the Linnean Society</mods:title>
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<mods:part id="155D5C97D7216139545AA21B0E437221">
<mods:date id="FF90E56F3D6AFC2635AEB1D74048D60F">2024</mods:date>
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<mods:number id="0254F954E3BCFC7896D0B0F0E0DC6219">2024-01-08</mods:number>
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<mods:number id="8FE650084551DE977BC1434D53E1D19B">202</mods:number>
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<treatment id="03CD9542FFAFFFFCECA73064D155FA1F" ID-DOI="http://doi.org/10.5281/zenodo.14269280" ID-Zenodo-Dep="14269280" LSID="urn:lsid:plazi:treatment:03CD9542FFAFFFFCECA73064D155FA1F" httpUri="http://treatment.plazi.org/id/03CD9542FFAFFFFCECA73064D155FA1F" lastPageId="19" lastPageNumber="20" pageId="2" pageNumber="3" scope_class="Amphibia" scope_family="Typhlonectidae" scope_order="Gymnophiona">
<subSubSection id="C37E77DFFFAFFFEDECA73064D0DDF9DB" box="[1023,1276,1613,1640]" pageId="2" pageNumber="3" type="nomenclature">
<paragraph id="8BDB2454FFAFFFEDECA73064D0DDF9DB" blockId="2.[1023,1276,1613,1640]" box="[1023,1276,1613,1640]" pageId="2" pageNumber="3">
<heading id="D0939338FFAFFFEDECA73064D0DDF9DB" bold="true" box="[1023,1276,1613,1640]" centered="true" fontSize="11" level="2" pageId="2" pageNumber="3" reason="2">
<emphasis id="B910F846FFAFFFEDECA73064D0DDF9DB" bold="true" box="[1023,1276,1613,1640]" pageId="2" pageNumber="3">
<taxonomicName id="4C645FD7FFAFFFEDECA73064D08AF9DB" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1023,1195,1613,1640]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="2" pageNumber="3" phylum="Chordata" rank="species" species="acrux" status="sp. nov.">
<emphasis id="B910F846FFAFFFEDECA73064D08AF9DB" bold="true" box="[1023,1195,1613,1640]" italics="true" pageId="2" pageNumber="3">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFAFFFEDEBE83067D0DDF9DB" box="[1200,1276,1614,1640]" pageId="2" pageNumber="3" rank="species">sp.nov.</taxonomicNameLabel>
</emphasis>
</heading>
</paragraph>
</subSubSection>
<subSubSection id="C37E77DFFFAFFFEDEC6130A7D08AF976" pageId="2" pageNumber="3" type="description">
<paragraph id="8BDB2454FFAFFFEDEC6130A7D08AF976" blockId="2.[825,1474,1678,1733]" pageId="2" pageNumber="3">
<emphasis id="B910F846FFAFFFEDEC6130A7D006F915" box="[825,1063,1678,1702]" italics="true" pageId="2" pageNumber="3">ZooBank registration:</emphasis>
urn:lsid:zoobank.org:act:D6487148- 6E74-436A -83C9-C89AC455B4BB
</paragraph>
</subSubSection>
<subSubSection id="C37E77DFFFAFFFEDEC6130C1D008F94C" box="[825,1065,1767,1791]" pageId="2" pageNumber="3" type="diagnosis">
<paragraph id="8BDB2454FFAFFFEDEC6130C1D008F94C" blockId="2.[825,1065,1767,1791]" box="[825,1065,1767,1791]" pageId="2" pageNumber="3">
<emphasis id="B910F846FFAFFFEDEC6130C1D7BEF94C" box="[825,927,1768,1791]" italics="true" pageId="2" pageNumber="3">Diagnosis:</emphasis>
As for genus.
</paragraph>
</subSubSection>
<subSubSection id="C37E77DFFFAFFFEBEC613109D0F6F8A4" lastPageId="4" lastPageNumber="5" pageId="2" pageNumber="3" type="materials_examined">
<paragraph id="8BDB2454FFAFFFEBEC613109D53DF8E6" blockId="2.[825,1474,1824,1974]" lastBlockId="4.[129,777,1728,1877]" lastPageId="4" lastPageNumber="5" pageId="2" pageNumber="3">
<materialsCitation id="3B0C2E09FFAFFFEDEC613109D0BBF805" collectionCode="DGM" country="Brazil" county="Tremembe" latitude="-22.94" location="Paraiba do Sul" longitude="-45.898613" pageId="2" pageNumber="3" specimenCode="DGM 1462*R" specimenCount="1" stateProvince="Sao Paulo" typeStatus="holotype">
<emphasis id="B910F846FFAFFFEDEC613109D7BFF88B" box="[825,926,1824,1848]" italics="true" pageId="2" pageNumber="3">
<typeStatus id="54DF9AF6FFAFFFEDEC613109D7B9F88B" box="[825,920,1824,1848]" pageId="2" pageNumber="3">Holotype</typeStatus>
:
</emphasis>
<specimenCode id="DBC28C2FFFAFFFEDECF13109D062F88B" box="[937,1091,1824,1848]" pageId="2" pageNumber="3">DGM 1462-R</specimenCode>
(
<figureCitation id="135F38D1FFAFFFEDEB003109D096F88B" box="[1112,1207,1824,1848]" captionStart-0="Figure 2" captionStart-1="Figure 3" captionStart-2="Figure 4" captionStart-3="Figure 5" captionStart-4="Figure 6" captionStart-5="Figure 7" captionStart-6="Figure 8" captionStart-7="Figure 9" captionStartId-0="3.[114,179,1836,1860]" captionStartId-1="4.[129,194,1627,1651]" captionStartId-2="5.[115,180,1628,1652]" captionStartId-3="6.[130,195,1627,1651]" captionStartId-4="7.[115,180,1627,1651]" captionStartId-5="8.[129,194,1626,1650]" captionStartId-6="9.[115,180,1627,1651]" captionStartId-7="10.[129,194,1629,1653]" captionTargetBox-0="[238,1336,144,1808]" captionTargetBox-1="[129,1473,144,1600]" captionTargetBox-2="[114,1458,144,1600]" captionTargetBox-3="[129,1473,144,1600]" captionTargetBox-4="[114,1458,144,1600]" captionTargetBox-5="[129,1473,142,1598]" captionTargetBox-6="[114,1458,144,1600]" captionTargetBox-7="[129,1473,145,1601]" captionTargetId-0="figure-8@3.[238,1336,144,1808]" captionTargetId-1="figure-140@4.[129,1473,144,1600]" captionTargetId-2="figure-107@5.[114,1458,144,1600]" captionTargetId-3="figure-131@6.[129,1473,144,1600]" captionTargetId-4="figure-181@7.[114,1458,144,1600]" captionTargetId-5="figure-120@8.[129,1473,142,1598]" captionTargetId-6="figure-148@9.[114,1458,144,1600]" captionTargetId-7="figure-150@10.[129,1473,145,1601]" captionTargetPageId-0="3" captionTargetPageId-1="4" captionTargetPageId-2="5" captionTargetPageId-3="6" captionTargetPageId-4="7" captionTargetPageId-5="8" captionTargetPageId-6="9" captionTargetPageId-7="10" captionText-0="Figure 2. Fossil slabs containing the holotype (DGM 1462-R) of Ymboirana acrux gen. et sp. nov. (A1, B1). CT-scans of the part (A2) and counterpart (B2) of the holotype.Scale bar = 1 cm." captionText-1="Figure 3. CT-scans of the two skull parts of Ymboirana acrux gen. et sp. nov. Top part in dorsal (A) and ventral (B) views. Bottom part in dorsal (C) and ventral (D) views. See Appendix for abbreviations.Scale bar = 1 mm." captionText-2="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." captionText-3="Figure 5. Lower jaw of Ymboirana acrux gen. et sp. nov. Mandibles in dorsal (A) and ventral (B) views.Left pseudangular in lateral (C), posterior oblique (D), and dorsal (E) views. Dotted lines indicate the region of the contact between the pseudangular and pseudodentary.See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A, B, and the lower one is for C–E." captionText-4="Figure 6. Isolated tooth crowns found near the skull of Ymboirana acruxgen.et sp. nov.. Scale bar = 1 mm." captionText-5="Figure 7. Vertebral column of Ymboirana acrux gen. et sp. nov. (A). Articulated trunk vertebrae from the posterior portion of the body in dorsal (B) and lateral (C) views. See Appendix for abbreviations. Upper scale bar = 1 cm. Lower scale bar = 1 mm; upper scale bar is for A, and the lower one is for B, C." captionText-6="Figure 8. Postcranial elements of Ymboirana acrux gen. et sp. nov.. Atlas in dorsal (A) and ventral (B) views. Ventral part of atlas (i.e. atlantal centrum and cotyles) in anterior (C), posterior (D), and oblique left lateral (E) views. Second vertebra in dorsal (F) and ventral (G) views.See Appendix for abbreviations.Scale bar = 1 mm." captionText-7="Figure 9. Postcranial elements of Ymboirana acrux gen. et sp.nov.. Trunk vertebra in dorsal (A), ventral (B), and oblique left lateral (C) views. Ribs (D, E) in lateral view. See Appendix for abbreviations. Scale bar = 1 mm." figureDoi-0="http://doi.org/10.5281/zenodo.14333145" figureDoi-1="http://doi.org/10.5281/zenodo.14333149" figureDoi-2="http://doi.org/10.5281/zenodo.14333151" figureDoi-3="http://doi.org/10.5281/zenodo.14333155" figureDoi-4="http://doi.org/10.5281/zenodo.14333157" figureDoi-5="http://doi.org/10.5281/zenodo.14333161" figureDoi-6="http://doi.org/10.5281/zenodo.14333163" figureDoi-7="http://doi.org/10.5281/zenodo.14333167" httpUri-0="https://zenodo.org/record/14333145/files/figure.png" httpUri-1="https://zenodo.org/record/14333149/files/figure.png" httpUri-2="https://zenodo.org/record/14333151/files/figure.png" httpUri-3="https://zenodo.org/record/14333155/files/figure.png" httpUri-4="https://zenodo.org/record/14333157/files/figure.png" httpUri-5="https://zenodo.org/record/14333161/files/figure.png" httpUri-6="https://zenodo.org/record/14333163/files/figure.png" httpUri-7="https://zenodo.org/record/14333167/files/figure.png" pageId="2" pageNumber="3">Figs 2–9</figureCitation>
,
<figureCitation id="135F38D1FFAFFFEDEB903109D0D5F88B" box="[1224,1268,1824,1848]" captionStart="Figure 12" captionStartId="15.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-115@15.[114,1458,144,1600]" captionTargetPageId="15" captionText="Figure 12. Paired parietals of four different caecilian species, all in dorsal view.Ymboirana acrux gen.et sp. nov.(A), Rhinatrema bivitatum (B), Tophlonectes natans (C), and Herpele squalostoma (D). See Appendix for abbreviations. Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333177" httpUri="https://zenodo.org/record/14333177/files/figure.png" pageId="2" pageNumber="3">12A</figureCitation>
,
<figureCitation id="135F38D1FFAFFFEDEA5E3109D113F88B" box="[1286,1330,1824,1848]" captionStart="Figure 13" captionStartId="16.[130,195,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-149@16.[129,1473,144,1600]" captionTargetPageId="16" captionText="Figure 13. Left stapes of six different caecilian species, all in lateral view.Fragment tentatively identified as the stapes of Ymboirana acrux gen. et sp.nov.(A), Potomotophlus kaupii (B), Tophlonectes natans (C), Caecilia sp. (D), Siphonops paulensis (E), and Rhinatrema bivitatum (F). See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333179" httpUri="https://zenodo.org/record/14333179/files/figure.png" pageId="2" pageNumber="3">13A</figureCitation>
,
<figureCitation id="135F38D1FFAFFFEDEA1C3109D150F88B" box="[1348,1393,1824,1848]" captionStart="Figure 14" captionStartId="17.[112,177,932,956]" captionTargetBox="[114,1458,143,904]" captionTargetId="figure-536@17.[114,1458,143,904]" captionTargetPageId="17" captionText="Figure 14. Left pseudangulars of four different caecilian species. Ymboirana acrux gen. et sp. nov. in lateral (A1) and dorsal (A2) views. Rhinatrema bivitatum in lateral (B1) and dorsal (B2) views. Scolecomorphus ulugurensis in lateral (C1) and dorsal (C2) views.Tophlonectes natans in lateral (D1) and dorsal (D2) views. See Appendix for abbreviations. Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333183" httpUri="https://zenodo.org/record/14333183/files/figure.png" pageId="2" pageNumber="3">14A</figureCitation>
,
<figureCitation id="135F38D1FFAFFFEDEADA3109D192F88B" box="[1410,1459,1824,1848]" captionStart="Figure 15" captionStartId="18.[129,194,1899,1923]" captionTargetBox="[129,1473,1111,1872]" captionTargetId="figure-568@18.[129,1473,1111,1872]" captionTargetPageId="18" captionText="Figure 15. Atlases of four different typhlonectid caecilians. Ymboirana acrux gen. et sp. nov. in anterior (A1) and dorsal (A2) views. Chthonerpeton indistinctum in anterior (B1) and dorsal (B2) views. Potomotophlus kaupii in anterior (C1) and dorsal (C2) views. Nectocaecilia petersii in anterior (D1) and dorsal (D2) views. See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333185" httpUri="https://zenodo.org/record/14333185/files/figure.png" pageId="2" pageNumber="3">15A</figureCitation>
<figureCitation id="135F38D1FFAFFFEDEAEC3109D19CF88B" box="[1460,1469,1824,1848]" captionStart="Figure 1" captionStartId="1.[113,178,1960,1984]" captionTargetBox="[116,1456,1173,1930]" captionTargetId="figure-558@1.[114,1458,1171,1932]" captionTargetPageId="1" captionText="Figure 1. Map of the Taubaté Basin in Southeastern Brazil, showing the type locality for Ymboirana acrux gen. et sp.nov.." figureDoi="http://doi.org/10.5281/zenodo.14333143" httpUri="https://zenodo.org/record/14333143/files/figure.png" pageId="2" pageNumber="3">1</figureCitation>
, A
<figureCitation id="135F38D1FFAFFFEDEC143169D779F8EB" box="[844,856,1856,1880]" captionStart="Figure 2" captionStartId="3.[114,179,1836,1860]" captionTargetBox="[238,1336,144,1808]" captionTargetId="figure-8@3.[238,1336,144,1808]" captionTargetPageId="3" captionText="Figure 2. Fossil slabs containing the holotype (DGM 1462-R) of Ymboirana acrux gen. et sp. nov. (A1, B1). CT-scans of the part (A2) and counterpart (B2) of the holotype.Scale bar = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.14333145" httpUri="https://zenodo.org/record/14333145/files/figure.png" pageId="2" pageNumber="3">2</figureCitation>
; Supporting Information,
<figureCitation id="135F38D1FFAFFFEDEB203169D0E9F8EB" box="[1144,1224,1856,1880]" captionStart="Figure 1" captionStartId="1.[113,178,1960,1984]" captionTargetBox="[116,1456,1173,1930]" captionTargetId="figure-558@1.[114,1458,1171,1932]" captionTargetPageId="1" captionText="Figure 1. Map of the Taubaté Basin in Southeastern Brazil, showing the type locality for Ymboirana acrux gen. et sp.nov.." figureDoi="http://doi.org/10.5281/zenodo.14333143" httpUri="https://zenodo.org/record/14333143/files/figure.png" pageId="2" pageNumber="3">Figs S1</figureCitation>
, S
<figureCitation id="135F38D1FFAFFFEDEBBA3169D0CEF8EB" box="[1250,1263,1856,1880]" captionStart="Figure 2" captionStartId="3.[114,179,1836,1860]" captionTargetBox="[238,1336,144,1808]" captionTargetId="figure-8@3.[238,1336,144,1808]" captionTargetPageId="3" captionText="Figure 2. Fossil slabs containing the holotype (DGM 1462-R) of Ymboirana acrux gen. et sp. nov. (A1, B1). CT-scans of the part (A2) and counterpart (B2) of the holotype.Scale bar = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.14333145" httpUri="https://zenodo.org/record/14333145/files/figure.png" pageId="2" pageNumber="3">2</figureCitation>
), housed at Museu de Ciências da Terra (formerly Divisão de Geologia e Mineralogia of the Departamento Nacional de Produção Mineral), Rio de Janeiro, Brazil
</materialsCitation>
. The specimen consists of part and counterpart preserving the anterior portion of a cae - cilian skeleton (with an estimated length of around
<quantity id="4C9C89B1FFA9FFEBEDEE30F6D6DCF944" box="[694,765,1759,1783]" metricMagnitude="-1" metricUnit="m" metricValue="2.0" pageId="4" pageNumber="5" unit="cm" value="20.0">20 cm</quantity>
), including skull, mandibles, and the anteriormost portion of the vertebral column, including the atlas, 66 trunk vertebrae, and some ribs.
</paragraph>
<caption id="DF1B74DCFFAEFFECEF2A3105D676F8D3" ID-DOI="http://doi.org/10.5281/zenodo.14333145" ID-Zenodo-Dep="14333145" httpUri="https://zenodo.org/record/14333145/files/figure.png" pageId="3" pageNumber="4" startId="3.[114,179,1836,1860]" targetBox="[238,1336,144,1808]" targetPageId="3" targetType="figure">
<paragraph id="8BDB2454FFAEFFECEF2A3105D676F8D3" blockId="3.[114,1409,1836,1888]" pageId="3" pageNumber="4">
<emphasis id="B910F846FFAEFFECEF2A3105D4EBF8F7" bold="true" box="[114,202,1836,1860]" pageId="3" pageNumber="4">Figure 2.</emphasis>
Fossil slabs containing the holotype (DGM 1462-R) of
<taxonomicName id="4C645FD7FFAEFFECED823105D757F8F7" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[730,886,1836,1860]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="3" pageNumber="4" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFAEFFECED823105D757F8F7" box="[730,886,1836,1860]" italics="true" pageId="3" pageNumber="4">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFAEFFECEC223104D022F8F7" box="[890,1027,1837,1861]" pageId="3" pageNumber="4" rank="species">gen. et sp. nov.</taxonomicNameLabel>
(A1, B1). CT -scans of the part (A2) and counterpart (B2) of the holotype. Scale bar = 1 cm.
</paragraph>
</caption>
<caption id="DF1B74DCFFA9FFEBEFD93072D77CF93C" ID-DOI="http://doi.org/10.5281/zenodo.14333149" ID-Zenodo-Dep="14333149" httpUri="https://zenodo.org/record/14333149/files/figure.png" pageId="4" pageNumber="5" startId="4.[129,194,1627,1651]" targetBox="[129,1473,144,1600]" targetPageId="4" targetType="figure">
<paragraph id="8BDB2454FFA9FFEBEFD93072D77CF93C" blockId="4.[129,1468,1627,1680]" pageId="4" pageNumber="5">
<emphasis id="B910F846FFA9FFEBEFD93072D4F9F9C7" bold="true" box="[129,216,1627,1652]" pageId="4" pageNumber="5">Figure 3.</emphasis>
CT -scans of the two skull parts of
<taxonomicName id="4C645FD7FFA9FFEBED443075D699F9C0" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[540,696,1628,1652]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="4" pageNumber="5" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFA9FFEBED443075D699F9C0" box="[540,696,1628,1652]" italics="true" pageId="4" pageNumber="5">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFA9FFEBEDE43075D764F9C0" box="[700,837,1628,1652]" pageId="4" pageNumber="5" rank="species">gen. et sp. nov.</taxonomicNameLabel>
Top part in dorsal (A) and ventral (B) views. Bottom part in dorsal (C) and ventral (D) views. See Appendix for abbreviations. Scale bar = 1 mm.
</paragraph>
</caption>
<paragraph id="8BDB2454FFA9FFEBEFD9315ED0F6F8A4" blockId="4.[129,778,1910,1965]" lastBlockId="4.[825,1475,1727,1815]" pageId="4" pageNumber="5">
<emphasis id="B910F846FFA9FFEBEFD9315ED5A5F83D" box="[129,388,1910,1934]" italics="true" pageId="4" pageNumber="5">Type locality and horizon:</emphasis>
Outcrop located on the right bank of the river
<location id="8EBB728FFFA9FFEBEFB831BCD556F81E" LSID="urn:lsid:plazi:treatment:03CD9542FFAFFFFCECA73064D155FA1F:8EBB728FFFA9FFEBEFB831BCD556F81E" box="[224,375,1941,1965]" country="Brazil" county="Tremembe" longitude="-45.898613" municipality="Sul" name="Paraiba do Sul" pageId="4" pageNumber="5" stateProvince="Sao Paulo">Paraíba do Sul</location>
,
<quantity id="4C9C89B1FFA9FFEBEEDB31BCD5EAF81E" box="[387,459,1941,1965]" metricMagnitude="3" metricUnit="m" metricValue="1.6" pageId="4" pageNumber="5" unit="km" value="1.6">
<locationDeviation id="9A693D76FFA9FFEBEEDB31BCD5EAF81E" box="[387,459,1941,1965]" metricMagnitude="3" metricUnit="m" metricValue="1.6" pageId="4" pageNumber="5" unit="km" value="1.6">1.6 km</locationDeviation>
</quantity>
north -east of the municipality of
<collectingCounty id="62BA5CD8FFA9FFEBEC0F30E9D7E8F96B" box="[855,969,1728,1752]" pageId="4" pageNumber="5">Tremembé</collectingCounty>
,
<collectingRegion id="49A0EAB6FFA9FFEBEC8D30E9D01FF96B" box="[981,1086,1728,1752]" country="Brazil" name="Sao Paulo" pageId="4" pageNumber="5">São Paulo</collectingRegion>
,
<collectingCountry id="F37364C4FFA9FFEBEB1230E9D0A4F96B" box="[1098,1157,1728,1752]" name="Brazil" pageId="4" pageNumber="5">Brazil</collectingCountry>
(
<geoCoordinate id="EE504293FFA9FFEBEBCD30E9D13BF96B" box="[1173,1306,1727,1752]" direction="south" orientation="latitude" pageId="4" pageNumber="5" value="-22.94">
22º94
<emphasis id="B910F846FFA9FFEBEB8E3096D0FDF96B" box="[1238,1244,1727,1752]" italics="true" pageId="4" pageNumber="5">ʹ</emphasis>
50
<emphasis id="B910F846FFA9FFEBEBAE3096D120F96B" box="[1270,1281,1727,1752]" italics="true" pageId="4" pageNumber="5">ʹʹ</emphasis>
S
</geoCoordinate>
;
<geoCoordinate id="EE504293FFA9FFEBEA7F30E9D197F96B" box="[1319,1462,1727,1752]" degrees="45" direction="west" minutes="53" orientation="longitude" pageId="4" pageNumber="5" precision="15" seconds="55" value="-45.898613">
45º53
<emphasis id="B910F846FFA9FFEBEA3D3096D14AF96B" box="[1381,1387,1727,1752]" italics="true" pageId="4" pageNumber="5">ʹ</emphasis>
55
<emphasis id="B910F846FFA9FFEBEADD3096D1B1F96B" box="[1413,1424,1727,1752]" italics="true" pageId="4" pageNumber="5">ʹʹ</emphasis>
W
</geoCoordinate>
). These deposits are assigned to the Oligocene age Tremembé Formation, and lie within Taubaté Basin.
</paragraph>
</subSubSection>
<subSubSection id="C37E77DFFFA9FFEBEC613111D10FF81D" pageId="4" pageNumber="5" type="etymology">
<paragraph id="8BDB2454FFA9FFEBEC613111D10FF81D" blockId="4.[825,1474,1848,1966]" pageId="4" pageNumber="5">
<emphasis id="B910F846FFA9FFEBEC613111D788F8E3" box="[825,937,1848,1872]" italics="true" pageId="4" pageNumber="5">Etymology:</emphasis>
The epithet is a noun in apposition and refers to
<taxonomicName id="4C645FD7FFA9FFEBEC61317ED798F8DC" authority="Crucis" authorityName="Crucis" box="[825,953,1879,1903]" class="Insecta" family="Acrididae" genus="Alpha" kingdom="Animalia" order="Orthoptera" pageId="4" pageNumber="5" phylum="Arthropoda" rank="genus">
<emphasis id="B910F846FFA9FFEBEC61317ED798F8DC" box="[825,953,1879,1903]" italics="true" pageId="4" pageNumber="5">Alpha Crucis</emphasis>
</taxonomicName>
, also known as
<location id="8EBB728FFFA9FFEBEB023171D119F8DC" LSID="urn:lsid:plazi:treatment:03CD9542FFAFFFFCECA73064D155FA1F:8EBB728FFFA9FFEBEB023171D119F8DC" box="[1114,1336,1879,1904]" name="Star of Magellan. This" pageId="4" pageNumber="5" stateProvince="Sao Paulo">Star of Magellan. This</location>
star (actually a multiple star system) represents, in the Brazilian national flag, the state of
<collectingRegion id="49A0EAB6FFA9FFEBECF631BFD032F81D" box="[942,1043,1942,1966]" country="Brazil" name="Sao Paulo" pageId="4" pageNumber="5">São Paulo</collectingRegion>
, where the fossil was found.
</paragraph>
</subSubSection>
<caption id="DF1B74DCFFA8FFEAEF2B3075D008F97B" ID-DOI="http://doi.org/10.5281/zenodo.14333151" ID-Zenodo-Dep="14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="5" pageNumber="6" startId="5.[115,180,1628,1652]" targetBox="[114,1458,144,1600]" targetPageId="5" targetType="figure">
<paragraph id="8BDB2454FFA8FFEAEF2B3075D008F97B" blockId="5.[113,1425,1628,1736]" pageId="5" pageNumber="6">
<emphasis id="B910F846FFA8FFEAEF2B3075D4EAF9C7" bold="true" box="[115,203,1628,1652]" pageId="5" pageNumber="6">Figure 4.</emphasis>
Skull bones of
<taxonomicName id="4C645FD7FFA8FFEAEE013075D5D4F9C7" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[345,501,1628,1652]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="5" pageNumber="6" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFA8FFEAEE013075D5D4F9C7" box="[345,501,1628,1652]" italics="true" pageId="5" pageNumber="6">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFA8FFEAEEA23074D6A2F9C7" box="[506,643,1629,1653]" pageId="5" pageNumber="6" rank="species">gen. et sp. nov.</taxonomicNameLabel>
Collapsed fragments of the posterolateral region of the
<taxonomicName id="4C645FD7FFA8FFEAEBD43074D0C1F9C7" box="[1164,1248,1628,1652]" class="Amphibia" family="Caeciliidae" genus="Oscaecilia" kingdom="Animalia" order="Gymnophiona" pageId="5" pageNumber="15" phylum="Chordata" rank="species" species="basale">os basale</taxonomicName>
below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the
<taxonomicName id="4C645FD7FFA8FFEAEBFD3050D0D8F923" box="[1189,1273,1656,1680]" class="Amphibia" family="Caeciliidae" genus="Oscaecilia" kingdom="Animalia" order="Gymnophiona" pageId="5" pageNumber="15" phylum="Chordata" rank="species" species="basale">os basale</taxonomicName>
in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations. Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G.
</paragraph>
</caption>
<subSubSection id="C37E77DFFFA8FFE4EE2E30DED164FB72" lastPageId="11" lastPageNumber="12" pageId="5" pageNumber="6" type="description">
<paragraph id="8BDB2454FFA8FFEAEE2E30DED5D7F8A2" blockId="5.[113,763,1783,1982]" box="[374,502,1783,1809]" pageId="5" pageNumber="6">
<emphasis id="B910F846FFA8FFEAEE2E30DED5D7F8A2" bold="true" box="[374,502,1783,1809]" pageId="5" pageNumber="6">Description</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA8FFEAEEC6310BD5EFF88F" blockId="5.[113,763,1783,1982]" box="[414,462,1826,1852]" pageId="5" pageNumber="6">
<emphasis id="B910F846FFA8FFEAEEC6310BD5EFF88F" box="[414,462,1826,1852]" italics="true" pageId="5" pageNumber="6">Skull</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA8FFEAEF293161D6DAF80D" blockId="5.[113,763,1783,1982]" pageId="5" pageNumber="6">
The skull is severely damaged and strongly dorsoventrally compressed (
<figureCitation id="135F38D1FFA8FFEAEFA63141D518F833" box="[254,313,1896,1920]" captionStart="Figure 3" captionStartId="4.[129,194,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-140@4.[129,1473,144,1600]" captionTargetPageId="4" captionText="Figure 3. CT-scans of the two skull parts of Ymboirana acrux gen. et sp. nov. Top part in dorsal (A) and ventral (B) views. Bottom part in dorsal (C) and ventral (D) views. See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333149" httpUri="https://zenodo.org/record/14333149/files/figure.png" pageId="5" pageNumber="6">Fig. 3</figureCitation>
). Most of the bones are broken into short or indistinct fragments; however, both parietals and the pos - terior portion of the left pseudangular are well preserved.
</paragraph>
<paragraph id="8BDB2454FFA8FFE9EC7230D1D5C5F89E" blockId="5.[810,1459,1784,1965]" lastBlockId="6.[129,778,1750,1837]" lastPageId="6" lastPageNumber="7" pageId="5" pageNumber="6">
Some fragments are tentatively assigned to the nasopremaxilla, maxillopalatine, frontals, squamosals, quadrates, stapes,
<taxonomicName id="4C645FD7FFA8FFEAEAC43131D74BF8FC" class="Amphibia" family="Caeciliidae" genus="Oscaecilia" kingdom="Animalia" order="Gymnophiona" pageId="5" pageNumber="15" phylum="Chordata" rank="species" species="basale">os basale</taxonomicName>
, and pseudodentaries. Many tooth crowns are also pre - sent, most of them disarticulated and a few still attached to their pedicels and to their corresponding jaw bones. Given that the skull bones may be difficult to distinguish due to the damaged condition of the fossil, we also provide a figure of the skull in the Supporting Information (
<figureCitation id="135F38D1FFABFFE9EED230DFD5F0F8BD" box="[394,465,1782,1806]" captionStart="Figure 2" captionStartId="3.[114,179,1836,1860]" captionTargetBox="[238,1336,144,1808]" captionTargetId="figure-8@3.[238,1336,144,1808]" captionTargetPageId="3" captionText="Figure 2. Fossil slabs containing the holotype (DGM 1462-R) of Ymboirana acrux gen. et sp. nov. (A1, B1). CT-scans of the part (A2) and counterpart (B2) of the holotype.Scale bar = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.14333145" httpUri="https://zenodo.org/record/14333145/files/figure.png" pageId="6" pageNumber="7">Fig. S2</figureCitation>
) with an outline line drawing and using lighter shades of colours.
</paragraph>
<caption id="DF1B74DCFFABFFE9EFDA3072D072F91F" ID-DOI="http://doi.org/10.5281/zenodo.14333155" ID-Zenodo-Dep="14333155" httpUri="https://zenodo.org/record/14333155/files/figure.png" pageId="6" pageNumber="7" startId="6.[130,195,1627,1651]" targetBox="[129,1473,144,1600]" targetPageId="6" targetType="figure">
<paragraph id="8BDB2454FFABFFE9EFDA3072D072F91F" blockId="6.[129,1460,1627,1708]" pageId="6" pageNumber="7">
<emphasis id="B910F846FFABFFE9EFDA3072D4FBF9C7" bold="true" box="[130,218,1627,1652]" pageId="6" pageNumber="7">Figure 5.</emphasis>
Lower jaw of
<taxonomicName id="4C645FD7FFABFFE9EE053075D5D8F9C0" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[349,505,1628,1652]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="6" pageNumber="7" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFABFFE9EE053075D5D8F9C0" box="[349,505,1628,1652]" italics="true" pageId="6" pageNumber="7">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFABFFE9EEA53075D6A7F9C0" box="[509,646,1628,1652]" pageId="6" pageNumber="7" rank="species">gen. et sp. nov.</taxonomicNameLabel>
Mandibles in dorsal (A) and ventral (B) views. Left pseudangular in lateral (C), posterior oblique (D), and dorsal (E) views. Dotted lines indicate the region of the contact between the pseudangular and pseudodentary. See Appendix for abbreviations. Scale bars = 1 mm; upper scale bar is for A, B, and the lower one is for C–E.
</paragraph>
</caption>
<paragraph id="8BDB2454FFABFFE9EFD93167D00AF8FF" blockId="6.[129,778,1870,1988]" lastBlockId="6.[825,1474,1750,1868]" pageId="6" pageNumber="7">
<emphasis id="B910F846FFABFFE9EFD93167D50CF8D5" box="[129,301,1870,1894]" italics="true" pageId="6" pageNumber="7">Nasopremaxillae:</emphasis>
Fragments of the presumed nasopremaxillae are present, identified primarily on the basis of their position. Due to their poor preservation, few diagnostic features can be ob - served. However, based on the relative position of the fragments in relation to the lower jaw, we interpret the nasopremaxillae as forming an anteriorly projected snout and, thus, the mouth to be subterminal. Several other fragments were also preserved but lack diagnostic features.
</paragraph>
<paragraph id="8BDB2454FFABFFE8EC613144D5F5F88A" blockId="6.[825,1474,1901,1988]" lastBlockId="7.[113,763,1700,1849]" lastPageId="7" lastPageNumber="8" pageId="6" pageNumber="7">
<emphasis id="B910F846FFABFFE9EC613144D7C5F836" box="[825,996,1901,1925]" italics="true" pageId="6" pageNumber="7">Maxillopalatines:</emphasis>
Both maxillopalatines are partially pre - served though severely damaged. The outer tooth rows of both maxillopalatines are present but incompletely preserved, so we could recognize only 12 pedicels. A fragment tentatively inter - preted as a portion of the left vomeropalatine tooth row is lo - cated medially and bears seven pedicels. Several other fragments, possibly belonging to the maxillopalatines, are present but do not exhibit any diagnostic features.
</paragraph>
<caption id="DF1B74DCFFAAFFE8EF2B3072D075F9C0" ID-DOI="http://doi.org/10.5281/zenodo.14333157" ID-Zenodo-Dep="14333157" box="[115,1108,1627,1652]" httpUri="https://zenodo.org/record/14333157/files/figure.png" pageId="7" pageNumber="8" startId="7.[115,180,1627,1651]" targetBox="[114,1458,144,1600]" targetPageId="7" targetType="figure">
<paragraph id="8BDB2454FFAAFFE8EF2B3072D075F9C0" blockId="7.[115,1108,1627,1652]" box="[115,1108,1627,1652]" pageId="7" pageNumber="8">
<emphasis id="B910F846FFAAFFE8EF2B3072D4EAF9C7" bold="true" box="[115,203,1627,1652]" pageId="7" pageNumber="8">Figure 6.</emphasis>
Isolated tooth crowns found near the skull of
<taxonomicName id="4C645FD7FFAAFFE8ED213075D734F9C0" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[633,789,1628,1652]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="7" pageNumber="8" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov">
<emphasis id="B910F846FFAAFFE8ED213075D734F9C0" box="[633,789,1628,1652]" italics="true" pageId="7" pageNumber="8">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFAAFFE8EC4F3075D7BAF9C0" box="[791,923,1628,1652]" pageId="7" pageNumber="8" rank="species">gen. et sp. nov</taxonomicNameLabel>
.. Scale bar = 1 mm.
</paragraph>
</caption>
<paragraph id="8BDB2454FFAAFFE8EF293173D131F8EB" blockId="7.[113,762,1882,2000]" lastBlockId="7.[810,1459,1699,1880]" pageId="7" pageNumber="8">
<emphasis id="B910F846FFAAFFE8EF293173D4ECF8C1" box="[113,205,1882,1906]" italics="true" pageId="7" pageNumber="8">Parietals:</emphasis>
These are the best -preserved skull bones in the spe - cimen and are almost complete, except for a short dorsolateral portion missing from the left. In dorsal view, except for their anterolateral pointed corners, both parietals exhibit a roughly trapezoidal shape (
<figureCitation id="135F38D1FFAAFFE8ECB5308AD01AF90F" box="[1005,1083,1699,1724]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="7" pageNumber="8">Figs 4A</figureCitation>
,
<figureCitation id="135F38D1FFAAFFE8EB1F308DD053F90F" box="[1095,1138,1700,1724]" captionStart="Figure 12" captionStartId="15.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-115@15.[114,1458,144,1600]" captionTargetPageId="15" captionText="Figure 12. Paired parietals of four different caecilian species, all in dorsal view.Ymboirana acrux gen.et sp. nov.(A), Rhinatrema bivitatum (B), Tophlonectes natans (C), and Herpele squalostoma (D). See Appendix for abbreviations. Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333177" httpUri="https://zenodo.org/record/14333177/files/figure.png" pageId="7" pageNumber="8">12A</figureCitation>
). The dorsal surface is smooth, lacking ornamentations in the form of small neurovascular for - amina that are common in some caecilians. The parietals are also flat medially but have a pronounced ventrally oriented slope at their posterolateral margins. Collapsed fragments of the
<taxonomicName id="4C645FD7FFAAFFE8EAC43108D749F8EB" class="Amphibia" family="Caeciliidae" genus="Oscaecilia" kingdom="Animalia" order="Gymnophiona" pageId="7" pageNumber="15" phylum="Chordata" rank="species" species="basale">os basale</taxonomicName>
cover the ventral surfaces of the parietals.
</paragraph>
<paragraph id="8BDB2454FFAAFFE7EC723150D68EF8A1" blockId="7.[810,1459,1913,2000]" lastBlockId="8.[129,777,1754,1810]" lastPageId="8" lastPageNumber="9" pageId="7" pageNumber="8">
<emphasis id="B910F846FFAAFFE8EC723150D7A0F822" box="[810,897,1913,1937]" italics="true" pageId="7" pageNumber="8">Frontals:</emphasis>
Located immediately anterior to both parietals, lie two poorly preserved bones, tentatively identified as parts of the frontals. They are broken and show an irregular shape, and similar to the parietals, the preserved portions of the dorsal sur - face of both frontals lack small neurovascular foramina.
</paragraph>
<caption id="DF1B74DCFFA5FFE7EFD93073D564F918" ID-DOI="http://doi.org/10.5281/zenodo.14333161" ID-Zenodo-Dep="14333161" httpUri="https://zenodo.org/record/14333161/files/figure.png" pageId="8" pageNumber="9" startId="8.[129,194,1626,1650]" targetBox="[129,1473,142,1598]" targetPageId="8" targetType="figure">
<paragraph id="8BDB2454FFA5FFE7EFD93073D564F918" blockId="8.[129,1471,1626,1707]" pageId="8" pageNumber="9">
<emphasis id="B910F846FFA5FFE7EFD93073D4F9F9C0" bold="true" box="[129,216,1626,1651]" pageId="8" pageNumber="9">Figure 7.</emphasis>
Vertebral column of
<taxonomicName id="4C645FD7FFA5FFE7EEC53073D618F9C1" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[413,569,1626,1650]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="8" pageNumber="9" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFA5FFE7EEC53073D618F9C1" box="[413,569,1626,1650]" italics="true" pageId="8" pageNumber="9">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFA5FFE7ED663072D6E6F9C1" box="[574,711,1627,1651]" pageId="8" pageNumber="9" rank="species">gen. et sp. nov.</taxonomicNameLabel>
(A). Articulated trunk vertebrae from the posterior portion of the body in dorsal (B) and lateral (C) views. See Appendix for abbreviations. Upper scale bar = 1 cm. Lower scale bar = 1 mm; upper scale bar is for A, and the lower one is for B, C.
</paragraph>
</caption>
<paragraph id="8BDB2454FFA5FFE7EFD9311AD72BF81A" blockId="8.[129,778,1843,1961]" pageId="8" pageNumber="9">
<emphasis id="B910F846FFA5FFE7EFD9311AD4DAF8F8" box="[129,251,1843,1867]" italics="true" pageId="8" pageNumber="9">Squamosals:</emphasis>
Some fragments are tentatively assigned to the left squamosal (
<figureCitation id="135F38D1FFA5FFE7EFA5317BD564F8D9" box="[253,325,1874,1898]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="8" pageNumber="9">Fig. 4F</figureCitation>
). They are located close to the left quadrate and above the left parietal. The squamosal is roughly rectangular and bears a postorbital process with a slightly concave margin.
</paragraph>
<paragraph id="8BDB2454FFA5FFE7EC6130F2D7B7F8A1" blockId="8.[825,1474,1754,1810]" pageId="8" pageNumber="9">The only evidence of ornamentation is a single neurovascular foramen.</paragraph>
<paragraph id="8BDB2454FFA5FFE6EC61311AD602F8C2" blockId="8.[825,1475,1843,1961]" lastBlockId="9.[113,763,1756,1905]" lastPageId="9" lastPageNumber="10" pageId="8" pageNumber="9">
<emphasis id="B910F846FFA5FFE7EC61311AD787F8F8" box="[825,934,1843,1867]" italics="true" pageId="8" pageNumber="9">Quadrates:</emphasis>
Both quadrates are preserved but broken (
<figureCitation id="135F38D1FFA5FFE7EA0A311AD1ADF8F8" box="[1362,1420,1843,1867]" captionStart="Figure 3" captionStartId="4.[129,194,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-140@4.[129,1473,144,1600]" captionTargetPageId="4" captionText="Figure 3. CT-scans of the two skull parts of Ymboirana acrux gen. et sp. nov. Top part in dorsal (A) and ventral (B) views. Bottom part in dorsal (C) and ventral (D) views. See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333149" httpUri="https://zenodo.org/record/14333149/files/figure.png" pageId="8" pageNumber="9">Figs 3</figureCitation>
,
<figureCitation id="135F38D1FFA5FFE7EACE311AD190F8F8" box="[1430,1457,1843,1867]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="8" pageNumber="9">4B</figureCitation>
). Portions of the left quadrate are located just above the articular facet of the pseudangular and not so widely separated from the maxillopalatines. The right quadrate is preserved far forward, next to fragments interpreted as parts of the pseudodentary. Due to the damaged condition of the squamosals, the degree of dorsal exposure of the quadrates cannot be determined. The pterygoid process of the left quadrate is present and elongate. A distinctive otic process is absent from both quadrates.
</paragraph>
<caption id="DF1B74DCFFA4FFE6EF2B3072D609F918" ID-DOI="http://doi.org/10.5281/zenodo.14333163" ID-Zenodo-Dep="14333163" httpUri="https://zenodo.org/record/14333163/files/figure.png" pageId="9" pageNumber="10" startId="9.[115,180,1627,1651]" targetBox="[114,1458,144,1600]" targetPageId="9" targetType="figure">
<paragraph id="8BDB2454FFA4FFE6EF2B3072D609F918" blockId="9.[113,1454,1627,1708]" pageId="9" pageNumber="10">
<emphasis id="B910F846FFA4FFE6EF2B3072D4EBF9C7" bold="true" box="[115,202,1627,1652]" pageId="9" pageNumber="10">Figure 8.</emphasis>
Postcranial elements of
<taxonomicName id="4C645FD7FFA4FFE6EEF63075D66BF9C0" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[430,586,1628,1652]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="9" pageNumber="10" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov">
<emphasis id="B910F846FFA4FFE6EEF63075D66BF9C0" box="[430,586,1628,1652]" italics="true" pageId="9" pageNumber="10">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFA4FFE6ED163075D6F3F9C0" box="[590,722,1628,1652]" pageId="9" pageNumber="10" rank="species">gen. et sp. nov</taxonomicNameLabel>
.. Atlas in dorsal (A) and ventral (B) views. Ventral part of atlas (i.e. atlantal centrum and cotyles) in anterior (C), posterior (D), and oblique left lateral (E) views. Second vertebra in dorsal (F) and ventral (G) views. See Appendix for abbreviations. Scale bar = 1 mm.
</paragraph>
</caption>
<paragraph id="8BDB2454FFA4FFE6EF2931BAD0AEF881" blockId="9.[113,763,1938,1993]" lastBlockId="9.[810,1459,1756,1842]" pageId="9" pageNumber="10">
<emphasis id="B910F846FFA4FFE6EF2931BAD496F819" box="[113,183,1939,1962]" italics="true" pageId="9" pageNumber="10">Stapes:</emphasis>
A small fragment located on the posterodorsal portion of the skull, close to the left quadrate, is tentatively interpreted as the left stapes (
<figureCitation id="135F38D1FFA4FFE6EC9B30F5D033F947" box="[963,1042,1756,1780]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="9" pageNumber="10">Figs 4G</figureCitation>
,
<figureCitation id="135F38D1FFA4FFE6EB4430F5D066F947" box="[1052,1095,1756,1780]" captionStart="Figure 13" captionStartId="16.[130,195,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-149@16.[129,1473,144,1600]" captionTargetPageId="16" captionText="Figure 13. Left stapes of six different caecilian species, all in lateral view.Fragment tentatively identified as the stapes of Ymboirana acrux gen. et sp.nov.(A), Potomotophlus kaupii (B), Tophlonectes natans (C), Caecilia sp. (D), Siphonops paulensis (E), and Rhinatrema bivitatum (F). See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333179" httpUri="https://zenodo.org/record/14333179/files/figure.png" pageId="9" pageNumber="10">13A</figureCitation>
). This fragment is composed of two different portions (i.e. a short and slender stapedial style and a small footplate) and is imperforate.
</paragraph>
<paragraph id="8BDB2454FFA4FFE5EC72317DD7ADF884" blockId="9.[810,1459,1875,1993]" lastBlockId="10.[825,1474,1729,1847]" lastPageId="10" lastPageNumber="11" pageId="9" pageNumber="10">
<emphasis id="B910F846FFA4FFE6EC72317DD7B1F8D8" box="[810,912,1875,1899]" italics="true" pageId="9" pageNumber="10">
<taxonomicName id="4C645FD7FFA4FFE6EC72317DD7AAF8D8" box="[810,907,1875,1899]" class="Amphibia" family="Caeciliidae" genus="Oscaecilia" kingdom="Animalia" order="Gymnophiona" pageId="9" pageNumber="10" phylum="Chordata" rank="species" species="basale">Os basale</taxonomicName>
:
</emphasis>
Several small broken parts, scattered about the skull but mainly at its posterior portion appear to represent different regions of the
<taxonomicName id="4C645FD7FFA4FFE6EC9E31BAD006F819" box="[966,1063,1938,1962]" class="Amphibia" family="Caeciliidae" genus="Oscaecilia" kingdom="Animalia" order="Gymnophiona" pageId="9" pageNumber="15" phylum="Chordata" rank="species" species="basale">os basale</taxonomicName>
. One of these fragments, located just behind the left pseudangular and still articulated with the atlas, corresponds to a posterior portion of the
<taxonomicName id="4C645FD7FFA7FFE5ED7830EBD65AF96A" box="[544,635,1729,1753]" class="Amphibia" family="Caeciliidae" genus="Oscaecilia" kingdom="Animalia" order="Gymnophiona" pageId="10" pageNumber="15" phylum="Chordata" rank="species" species="basale">os basale</taxonomicName>
, including the left occipital condyle (
<figureCitation id="135F38D1FFA7FFE5EE3130C9D5F0F94A" box="[361,465,1760,1785]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="10" pageNumber="11">Fig. 4C–E</figureCitation>
; Supporting Information,
<figureCitation id="135F38D1FFA7FFE5EDBB30C9D4BAF8AB" captionStart="Figure 1" captionStartId="1.[113,178,1960,1984]" captionTargetBox="[116,1456,1173,1930]" captionTargetId="figure-558@1.[114,1458,1171,1932]" captionTargetPageId="1" captionText="Figure 1. Map of the Taubaté Basin in Southeastern Brazil, showing the type locality for Ymboirana acrux gen. et sp.nov.." figureDoi="http://doi.org/10.5281/zenodo.14333143" httpUri="https://zenodo.org/record/14333143/files/figure.png" pageId="10" pageNumber="11">Fig. S1</figureCitation>
). A jugular foramen is present just anterior to the condyle. The region of the otic capsule is located anterior to the jugular foramen, but its external wall is badly damaged, whereas parts of the internal walls of the otic capsule are better preserved and bear the perilymphatic foramen and other foramina for branches of the auditory nerve. A large fragment preserved collapsed on the ventral surface of the right parietal bears a carotid for - amen (
<figureCitation id="135F38D1FFA7FFE5ECDC30C9D7EEF94A" box="[900,975,1760,1785]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="10" pageNumber="11">Fig. 4A</figureCitation>
), and lateral to this foramen, a lip of bone with a distinctive articular surface is interpreted as the basipterygoid process.
</paragraph>
<caption id="DF1B74DCFFA7FFE5EFD93074D779F922" ID-DOI="http://doi.org/10.5281/zenodo.14333167" ID-Zenodo-Dep="14333167" httpUri="https://zenodo.org/record/14333167/files/figure.png" pageId="10" pageNumber="11" startId="10.[129,194,1629,1653]" targetBox="[129,1473,145,1601]" targetPageId="10" targetType="figure">
<paragraph id="8BDB2454FFA7FFE5EFD93074D779F922" blockId="10.[129,1457,1629,1681]" pageId="10" pageNumber="11">
<emphasis id="B910F846FFA7FFE5EFD93074D4F8F9C6" bold="true" box="[129,217,1629,1653]" pageId="10" pageNumber="11">Figure 9.</emphasis>
Postcranial elements of
<taxonomicName id="4C645FD7FFA7FFE5EEE43074D679F9C6" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[444,600,1629,1653]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="10" pageNumber="11" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov">
<emphasis id="B910F846FFA7FFE5EEE43074D679F9C6" box="[444,600,1629,1653]" italics="true" pageId="10" pageNumber="11">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFA7FFE5ED053077D6C1F9C6" box="[605,736,1630,1654]" pageId="10" pageNumber="11" rank="species">gen. et sp. nov</taxonomicNameLabel>
.. Trunk vertebra in dorsal (A), ventral (B), and oblique left lateral (C) views. Ribs (D, E) in lateral view. See Appendix for abbreviations. Scale bar = 1 mm.
</paragraph>
</caption>
<paragraph id="8BDB2454FFA7FFE5EB15317ED08EF8C3" blockId="10.[825,1474,1879,1973]" box="[1101,1199,1879,1904]" pageId="10" pageNumber="11">
<emphasis id="B910F846FFA7FFE5EB15317ED08EF8C3" box="[1101,1199,1879,1904]" italics="true" pageId="10" pageNumber="11">Lower jaw</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA7FFE4EC613154D678FD8C" blockId="10.[825,1474,1879,1973]" lastBlockId="11.[113,763,144,575]" lastPageId="11" lastPageNumber="12" pageId="10" pageNumber="11">
<emphasis id="B910F846FFA7FFE5EC613154D7ECF826" box="[825,973,1917,1941]" italics="true" pageId="10" pageNumber="11">Pseudangulars:</emphasis>
Only the well -preserved posteriormost portion of the left pseudangular is discernable (
<figureCitation id="135F38D1FFA7FFE5EB9431B5D139F806" box="[1228,1304,1948,1973]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="10" pageNumber="11">Figs 4B</figureCitation>
,
<figureCitation id="135F38D1FFA7FFE5EA7B31B5D17EF807" box="[1315,1375,1948,1972]" captionStart="Figure 5" captionStartId="6.[130,195,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-131@6.[129,1473,144,1600]" captionTargetPageId="6" captionText="Figure 5. Lower jaw of Ymboirana acrux gen. et sp. nov. Mandibles in dorsal (A) and ventral (B) views.Left pseudangular in lateral (C), posterior oblique (D), and dorsal (E) views. Dotted lines indicate the region of the contact between the pseudangular and pseudodentary.See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A, B, and the lower one is for C–E." figureDoi="http://doi.org/10.5281/zenodo.14333155" httpUri="https://zenodo.org/record/14333155/files/figure.png" pageId="10" pageNumber="11">5C–E</figureCitation>
,
<figureCitation id="135F38D1FFA7FFE5EA3331B4D1B4F806" box="[1387,1429,1949,1973]" captionStart="Figure 14" captionStartId="17.[112,177,932,956]" captionTargetBox="[114,1458,143,904]" captionTargetId="figure-536@17.[114,1458,143,904]" captionTargetPageId="17" captionText="Figure 14. Left pseudangulars of four different caecilian species. Ymboirana acrux gen. et sp. nov. in lateral (A1) and dorsal (A2) views. Rhinatrema bivitatum in lateral (B1) and dorsal (B2) views. Scolecomorphus ulugurensis in lateral (C1) and dorsal (C2) views.Tophlonectes natans in lateral (D1) and dorsal (D2) views. See Appendix for abbreviations. Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333183" httpUri="https://zenodo.org/record/14333183/files/figure.png" pageId="10" pageNumber="11">14A</figureCitation>
). In lateral view, a recurved retroarticular process is present, bearing a well -developed lateral crest. The sutural surface that contacts the pseudodentary is excavated in the anterolateral margin. The processus condyloides is limited to a weakly developed process. In dorsal view, the articular surface is anteriorly positioned, concave, and surrounded posteriorly by the short processus condyloides. There are no signs of a preserved fossa or a canalis primordialis immediately anterior to the articular surface. The distinct processus internus is present, anteromedially oriented, and shows a roughly quadrangular outline. The retroarticular process curves medially mainly along its posterior portion. In medial view, two foramina of the ramus intermandibularis are present, one located at the posterior base of the processus internus and the other excavated anteriorly to it.
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EF293448D6D3FC01" blockId="11.[113,763,609,946]" pageId="11" pageNumber="12">
<emphasis id="B910F846FFA6FFE4EF293448D534FDCA" box="[113,277,609,633]" italics="true" pageId="11" pageNumber="12">Pseudodentaries:</emphasis>
Both pseudodentaries are partially preserved, including the region of the mandibular symphysis (
<figureCitation id="135F38D1FFA6FFE4EDDC34A9D6C8FD24" box="[644,745,640,664]" captionStart="Figure 5" captionStartId="6.[130,195,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-131@6.[129,1473,144,1600]" captionTargetPageId="6" captionText="Figure 5. Lower jaw of Ymboirana acrux gen. et sp. nov. Mandibles in dorsal (A) and ventral (B) views.Left pseudangular in lateral (C), posterior oblique (D), and dorsal (E) views. Dotted lines indicate the region of the contact between the pseudangular and pseudodentary.See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A, B, and the lower one is for C–E." figureDoi="http://doi.org/10.5281/zenodo.14333155" httpUri="https://zenodo.org/record/14333155/files/figure.png" pageId="11" pageNumber="12">Fig. 5A, B</figureCitation>
). Whereas the left one is represented by its anteriormost portion, in the right one the posterior portion is also preserved. Pedicels are present in the dorsal surface of the right pseudodentary, al - though the exact number is difficult to estimate. The pedicels are arranged in two rows, with definitive inner mandibular (i.e. splenial) pedicels being limited to the symphyseal region (based on the preserved pedicels, at least four are present on the right pseudodentary). The outer tooth row is also represented only by damaged pedicels, and we are able to recognize just 16 of them.
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EED135FBD5C3FC58" blockId="11.[113,763,978,1353]" box="[393,482,978,1003]" pageId="11" pageNumber="12">
<emphasis id="B910F846FFA6FFE4EED135FBD5C3FC58" box="[393,482,978,1003]" italics="true" pageId="11" pageNumber="12">Dentition</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EF2935D1D56EFAFA" blockId="11.[113,763,978,1353]" pageId="11" pageNumber="12">
We recognized at least 48 scattered tooth crowns near the skull (
<figureCitation id="135F38D1FFA6FFE4EF24323ED499FB9C" box="[124,184,1047,1071]" captionStart="Figure 6" captionStartId="7.[115,180,1627,1651]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-181@7.[114,1458,144,1600]" captionTargetPageId="7" captionText="Figure 6. Isolated tooth crowns found near the skull of Ymboirana acruxgen.et sp. nov.. Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333157" httpUri="https://zenodo.org/record/14333157/files/figure.png" pageId="11" pageNumber="12">Fig. 6</figureCitation>
). Some teeth were also preserved still attached to the pedicels. Most of them are similar in size (around
<quantity id="4C9C89B1FFA6FFE4EDD3321FD6FCFBFD" box="[651,733,1078,1102]" metricMagnitude="-4" metricUnit="m" metricValue="5.0" pageId="11" pageNumber="12" unit="mm" value="0.5">0.5 mm</quantity>
in length) and shape: slender, conical, recurved, and monocusped. Based on the size of the preserved pedicels, the teeth of the inner rows are a little smaller than those of the outer rows. The apex is pointed but lateral flanges are seemingly absent. Due to the dam - aged condition of the fossil, it was not possible to verify the exact total number of teeth; however, the pedicel arrangement allows confirmation of the ancestral caecilian double tooth rows in the upper and lower jaws.
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EE233343D5D1FA30" blockId="11.[113,763,1386,1573]" box="[379,496,1386,1411]" pageId="11" pageNumber="12">
<emphasis id="B910F846FFA6FFE4EE233343D5D1FA30" box="[379,496,1386,1411]" italics="true" pageId="11" pageNumber="12">Postcranium</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EF2933A6D6DBF996" blockId="11.[113,763,1386,1573]" pageId="11" pageNumber="12">
Postcranial elements assigned to
<taxonomicName id="4C645FD7FFA6FFE4EE9C33A6D64CFA14" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[452,621,1423,1447]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="11" pageNumber="12" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFA6FFE4EE9C33A6D64CFA14" box="[452,621,1423,1447]" italics="true" pageId="11" pageNumber="12">Ymboirana acrux</emphasis>
</taxonomicName>
comprise the fragmented atlas followed by 66 subsequent vertebrae (most of them still articulated, although in the median portion of the vertebral column they are scattered) and some ribs (
<figureCitation id="135F38D1FFA6FFE4EDD433C4D6E4F9B6" box="[652,709,1517,1541]" captionStart="Figure 7" captionStartId="8.[129,194,1626,1650]" captionTargetBox="[129,1473,142,1598]" captionTargetId="figure-120@8.[129,1473,142,1598]" captionTargetPageId="8" captionText="Figure 7. Vertebral column of Ymboirana acrux gen. et sp. nov. (A). Articulated trunk vertebrae from the posterior portion of the body in dorsal (B) and lateral (C) views. See Appendix for abbreviations. Upper scale bar = 1 cm. Lower scale bar = 1 mm; upper scale bar is for A, and the lower one is for B, C." figureDoi="http://doi.org/10.5281/zenodo.14333161" httpUri="https://zenodo.org/record/14333161/files/figure.png" pageId="11" pageNumber="12">Fig. 7</figureCitation>
). An unknown number of posteriormost vertebrae are not preserved.
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EF29306FD78DFF55" blockId="11.[113,763,1606,1974]" lastBlockId="11.[810,1460,144,230]" pageId="11" pageNumber="12">
<emphasis id="B910F846FFA6FFE4EF29306FD48AF9ED" box="[113,171,1606,1630]" italics="true" pageId="11" pageNumber="12">Atlas:</emphasis>
Broken elements interpreted as the atlantal centrum and the neural arch were preserved separately in the two slabs (
<figureCitation id="135F38D1FFA6FFE4ED88304CD48DF92E" captionStart="Figure 8" captionStartId="9.[115,180,1627,1651]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-148@9.[114,1458,144,1600]" captionTargetPageId="9" captionText="Figure 8. Postcranial elements of Ymboirana acrux gen. et sp. nov.. Atlas in dorsal (A) and ventral (B) views. Ventral part of atlas (i.e. atlantal centrum and cotyles) in anterior (C), posterior (D), and oblique left lateral (E) views. Second vertebra in dorsal (F) and ventral (G) views.See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333163" httpUri="https://zenodo.org/record/14333163/files/figure.png" pageId="11" pageNumber="12">Figs 8A–E</figureCitation>
,
<figureCitation id="135F38D1FFA6FFE4EFE230ADD4CBF92F" box="[186,234,1668,1692]" captionStart="Figure 15" captionStartId="18.[129,194,1899,1923]" captionTargetBox="[129,1473,1111,1872]" captionTargetId="figure-568@18.[129,1473,1111,1872]" captionTargetPageId="18" captionText="Figure 15. Atlases of four different typhlonectid caecilians. Ymboirana acrux gen. et sp. nov. in anterior (A1) and dorsal (A2) views. Chthonerpeton indistinctum in anterior (B1) and dorsal (B2) views. Potomotophlus kaupii in anterior (C1) and dorsal (C2) views. Nectocaecilia petersii in anterior (D1) and dorsal (D2) views. See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333185" httpUri="https://zenodo.org/record/14333185/files/figure.png" pageId="11" pageNumber="12">15A</figureCitation>
<figureCitation id="135F38D1FFA6FFE4EFB230ADD4D2F92F" box="[234,243,1668,1692]" captionStart="Figure 1" captionStartId="1.[113,178,1960,1984]" captionTargetBox="[116,1456,1173,1930]" captionTargetId="figure-558@1.[114,1458,1171,1932]" captionTargetPageId="1" captionText="Figure 1. Map of the Taubaté Basin in Southeastern Brazil, showing the type locality for Ymboirana acrux gen. et sp.nov.." figureDoi="http://doi.org/10.5281/zenodo.14333143" httpUri="https://zenodo.org/record/14333143/files/figure.png" pageId="11" pageNumber="12">1</figureCitation>
, A
<figureCitation id="135F38D1FFA6FFE4EE4A30ACD53FF92E" box="[274,286,1669,1693]" captionStart="Figure 2" captionStartId="3.[114,179,1836,1860]" captionTargetBox="[238,1336,144,1808]" captionTargetId="figure-8@3.[238,1336,144,1808]" captionTargetPageId="3" captionText="Figure 2. Fossil slabs containing the holotype (DGM 1462-R) of Ymboirana acrux gen. et sp. nov. (A1, B1). CT-scans of the part (A2) and counterpart (B2) of the holotype.Scale bar = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.14333145" httpUri="https://zenodo.org/record/14333145/files/figure.png" pageId="11" pageNumber="12">2</figureCitation>
). Both atlantal cotyles are present and fused anteroventrally but with a pronounced median notch between them. The spinal nerve foramen is preserved only in the pos - terior surface of the left cotyle and is oriented posterolaterally. The centrum has a length considerably shorter than the fol - lowing vertebrae, and its ventral surface is smooth, bearing a medially positioned fossa and no hypapophyseal keel. The pos - terior cotyle has a roughly oval outline and the notochordal fossa is deep. Only a few portions of the neural arch were preserved. Two separated and anteriorly directed projections are present and are interpreted as the anterior bases of the lateral pedicles. The dorsal surface of the atlas is smooth, with no evidence of a neural spine.
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EC723721D7F3FE48" blockId="11.[810,1460,264,507]" pageId="11" pageNumber="12">
<emphasis id="B910F846FFA6FFE4EC723721D7F2FE93" box="[810,979,264,288]" italics="true" pageId="11" pageNumber="12">Second vertebra:</emphasis>
The second vertebra is preserved still ar - ticulated to the atlas, but severely damaged (
<figureCitation id="135F38D1FFA6FFE4EA50370ED153FE8C" box="[1288,1394,295,319]" captionStart="Figure 8" captionStartId="9.[115,180,1627,1651]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-148@9.[114,1458,144,1600]" captionTargetPageId="9" captionText="Figure 8. Postcranial elements of Ymboirana acrux gen. et sp. nov.. Atlas in dorsal (A) and ventral (B) views. Ventral part of atlas (i.e. atlantal centrum and cotyles) in anterior (C), posterior (D), and oblique left lateral (E) views. Second vertebra in dorsal (F) and ventral (G) views.See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333163" httpUri="https://zenodo.org/record/14333163/files/figure.png" pageId="11" pageNumber="12">Fig. 8F, G</figureCitation>
). The neural arch is completely collapsed over the centrum. The two prezygapophyses are preserved and exhibit a flat articular surface. On the ventral surface of the centrum, there is a well -developed hypapophyseal keel, but basapophyseal processes seem to be ab - sent. No rib -like elements can be confidently identified near the second vertebra.
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EC723435D059FC1E" blockId="11.[810,1459,540,941]" pageId="11" pageNumber="12">
<emphasis id="B910F846FFA6FFE4EC723435D7F0FD87" box="[810,977,540,564]" italics="true" pageId="11" pageNumber="12">Trunk vertebrae:</emphasis>
The exact number of preserved trunk verte - brae (
<figureCitation id="135F38D1FFA6FFE4EC323415D78BFDE0" box="[874,938,572,596]" captionStart="Figure 7" captionStartId="8.[129,194,1626,1650]" captionTargetBox="[129,1473,142,1598]" captionTargetId="figure-120@8.[129,1473,142,1598]" captionTargetPageId="8" captionText="Figure 7. Vertebral column of Ymboirana acrux gen. et sp. nov. (A). Articulated trunk vertebrae from the posterior portion of the body in dorsal (B) and lateral (C) views. See Appendix for abbreviations. Upper scale bar = 1 cm. Lower scale bar = 1 mm; upper scale bar is for A, and the lower one is for B, C." figureDoi="http://doi.org/10.5281/zenodo.14333161" httpUri="https://zenodo.org/record/14333161/files/figure.png" pageId="11" pageNumber="12">Figs 7</figureCitation>
,
<figureCitation id="135F38D1FFA6FFE4ECE13415D7D7FDE7" box="[953,1014,572,596]" captionStart="Figure 9" captionStartId="10.[129,194,1629,1653]" captionTargetBox="[129,1473,145,1601]" captionTargetId="figure-150@10.[129,1473,145,1601]" captionTargetPageId="10" captionText="Figure 9. Postcranial elements of Ymboirana acrux gen. et sp.nov.. Trunk vertebra in dorsal (A), ventral (B), and oblique left lateral (C) views. Ribs (D, E) in lateral view. See Appendix for abbreviations. Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333167" httpUri="https://zenodo.org/record/14333167/files/figure.png" pageId="11" pageNumber="12">9A–C</figureCitation>
) cannot be determined because of exten - sive fragmentation and disarticulation. All of these vertebrae show diagenetic dorsoventral compression. They are elongate anteroposteriorly and have medially constricted amphicoelous centra, well -developed basapophyseal processes projecting anteroventrally, a pronounced hypapophyseal keel, and low neural arches. Poorly developed neural spines, limited to faint ridges, are present in some, but not all, of the posteriormost pre - served vertebrae. Basapophyseal processes bear well -developed and convex ventral ridges, and this feature is particularly pro - nounced in some vertebrae preserved at the posterior region of the
<typeStatus id="54DF9AF6FFA6FFE4EC0835BDD78DFC1F" box="[848,940,916,940]" pageId="11" pageNumber="12" type="holotype">holotype</typeStatus>
(
<figureCitation id="135F38D1FFA6FFE4ECE535BDD005FC1F" box="[957,1060,916,940]" captionStart="Figure 7" captionStartId="8.[129,194,1626,1650]" captionTargetBox="[129,1473,142,1598]" captionTargetId="figure-120@8.[129,1473,142,1598]" captionTargetPageId="8" captionText="Figure 7. Vertebral column of Ymboirana acrux gen. et sp. nov. (A). Articulated trunk vertebrae from the posterior portion of the body in dorsal (B) and lateral (C) views. See Appendix for abbreviations. Upper scale bar = 1 cm. Lower scale bar = 1 mm; upper scale bar is for A, and the lower one is for B, C." figureDoi="http://doi.org/10.5281/zenodo.14333161" httpUri="https://zenodo.org/record/14333161/files/figure.png" pageId="11" pageNumber="12">Figs 7B, C</figureCitation>
,
<figureCitation id="135F38D1FFA6FFE4EB7735BDD049FC1F" box="[1071,1128,916,940]" captionStart="Figure 9" captionStartId="10.[129,194,1629,1653]" captionTargetBox="[129,1473,145,1601]" captionTargetId="figure-150@10.[129,1473,145,1601]" captionTargetPageId="10" captionText="Figure 9. Postcranial elements of Ymboirana acrux gen. et sp.nov.. Trunk vertebra in dorsal (A), ventral (B), and oblique left lateral (C) views. Ribs (D, E) in lateral view. See Appendix for abbreviations. Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333167" httpUri="https://zenodo.org/record/14333167/files/figure.png" pageId="11" pageNumber="12">9B, C</figureCitation>
).
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EC7235E7D164FB72" blockId="11.[810,1460,974,1218]" pageId="11" pageNumber="12">
<emphasis id="B910F846FFA6FFE4EC7235E7D77DFC55" box="[810,860,974,998]" italics="true" pageId="11" pageNumber="12">Ribs:</emphasis>
Preserved ribs are hard to distinguish. Some are still articu - lated with vertebrae, but some are isolated and are relatively well preserved (
<figureCitation id="135F38D1FFA6FFE4ECFA3225D02CFB97" box="[930,1037,1036,1060]" captionStart="Figure 9" captionStartId="10.[129,194,1629,1653]" captionTargetBox="[129,1473,145,1601]" captionTargetId="figure-150@10.[129,1473,145,1601]" captionTargetPageId="10" captionText="Figure 9. Postcranial elements of Ymboirana acrux gen. et sp.nov.. Trunk vertebra in dorsal (A), ventral (B), and oblique left lateral (C) views. Ribs (D, E) in lateral view. See Appendix for abbreviations. Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333167" httpUri="https://zenodo.org/record/14333167/files/figure.png" pageId="11" pageNumber="12">Fig. 9D, E</figureCitation>
). They have a relatively straight outline along their entire length, lacking pronounced posterior flexion. The ribs are dorsoventrally broad anteriorly, but they gradually narrow distally. The tuberculum and capitulum have straight or more rounded tips, whereas the distal tips are pointed. The capit - ulum is very elongate anteriorly in the preserved ribs.
</paragraph>
</subSubSection>
<subSubSection id="C37E77DFFFA6FFFCEB4D32D1D155FA1F" lastPageId="19" lastPageNumber="20" pageId="11" pageNumber="12" type="discussion">
<paragraph id="8BDB2454FFA6FFE4EB4D32D1D0E9FAA1" blockId="11.[810,1459,1272,1810]" box="[1045,1224,1272,1298]" pageId="11" pageNumber="12">
<emphasis id="B910F846FFA6FFE4EB4D32D1D0E9FAA1" bold="true" box="[1045,1224,1272,1298]" pageId="11" pageNumber="12">DISCUSSION</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EC72330DD06FF8A1" blockId="11.[810,1459,1272,1810]" pageId="11" pageNumber="12">
The assignment of
<taxonomicName id="4C645FD7FFA6FFE4ECAF330DD085FA8F" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1015,1188,1316,1340]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="11" pageNumber="12" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFA6FFE4ECAF330DD085FA8F" box="[1015,1188,1316,1340]" italics="true" pageId="11" pageNumber="12">Ymboirana acrux</emphasis>
</taxonomicName>
to
<taxonomicName id="4C645FD7FFA6FFE4EB95330DD142FA8F" authorityName="Rafinesque" authorityYear="1814" box="[1229,1379,1316,1340]" class="Amphibia" kingdom="Animalia" order="Gymnophiona" pageId="11" pageNumber="12" phylum="Chordata" rank="order">Gymnophiona</taxonomicName>
is sup - ported by several uniquely derived features, such as the pres - ence of pseudangulars, pseudodentaries, and amphicoelous vertebrae bearing medially constricted centra, pronounced hypapophyseal keels, and anterior basapophyseal processes (
<bibRefCitation id="EFF559A5FFA6FFE4EC6D33E8D792FA6A" author="Wake MH" box="[821,947,1473,1497]" pageId="11" pageNumber="12" pagination="117 - 30" refId="ref13684" refString="Wake MH. Morphometrics of the skeleton of Dermophis mexicanus (Amphibia: Gymnophiona) Part I The vertebrae, with comparisons to other species. Journal of Morphologo 1980; 165: 117 - 30. https: // doi. org / 10.1002 / jmor. 1051650202" type="journal article" year="1980">
<collectingCountry id="F37364C4FFA6FFE4EC6D33E8D74FFA6A" box="[821,878,1473,1497]" name="Wake Island" pageId="11" pageNumber="12">Wake</collectingCountry>
1980
</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFA6FFE4EC9133E8D10CFA6A" author="Wilkinson M &amp; Nussbaum RA" box="[969,1325,1473,1497]" pageId="11" pageNumber="12" pagination="39 - 78" refId="ref14170" refString="Wilkinson M, Nussbaum RA. Caecilian phylogeny and classification. In: Exbrayat JM (ed.), Reproductive Biologo and Phologeno of Gomnophiona (Caecilians). Enfield: Science Publishers, 2006, 39 - 78." type="book chapter" year="2006">Wilkinson and Nussbaum 2006</bibRefCitation>
). The Late Triassic
<emphasis id="B910F846FFA6FFE4EC2633C8D075FA4B" box="[894,1108,1504,1528]" italics="true" pageId="11" pageNumber="12">Funcusvermis gilmorei</emphasis>
<bibRefCitation id="EFF559A5FFA6FFE4EB0233C9D100FA4B" author="Kligman BT &amp; Gee BM &amp; Marsh AD" box="[1114,1313,1504,1528]" pageId="11" pageNumber="12" pagination="102 - 7" refId="ref12069" refString="Kligman BT, Gee BM, Marsh AD et al. Triassic stem caecilian supports dissorophoid origin of living amphibians. Nature 2023; 614: 102 - 7. https: // doi. org / 10.1038 / s 41586 * 022 * 05646 * 5" type="journal article" year="2023">
Kligman
<emphasis id="B910F846FFA6FFE4EBEF33C8D0C6FA4B" box="[1207,1255,1504,1528]" italics="true" pageId="11" pageNumber="12">et al.</emphasis>
2023
</bibRefCitation>
, Early Jurassic
<taxonomicName id="4C645FD7FFA6FFE4EC7233D6D0DAF9A4" authority="Jenkins and Walsh 1993" authorityName="Jenkins and Walsh" authorityYear="1993" box="[810,1275,1535,1559]" class="Amphibia" family="Eocaeciliaidae" genus="Eocaecilia" higherTaxonomySource="GBIF" kingdom="Animalia" order="Gymnophiona" pageId="11" pageNumber="12" phylum="Chordata" rank="species" species="micropodia">
<emphasis id="B910F846FFA6FFE4EC7233D6D7DFF9A4" box="[810,1022,1535,1559]" italics="true" pageId="11" pageNumber="12">Eocaecilia micropodia</emphasis>
<bibRefCitation id="EFF559A5FFA6FFE4EB5C33D6D0DAF9A4" author="Jenkins FA &amp; Walsh DM" box="[1028,1275,1535,1559]" pageId="11" pageNumber="12" pagination="246 - 50" refId="ref11892" refString="Jenkins FA, Walsh DM. An Early Jurassic caecilian with limbs. Nature 1993; 365: 246 - 50." type="journal article" year="1993">Jenkins and Walsh 1993</bibRefCitation>
</taxonomicName>
, Early Cretaceous
<taxonomicName id="4C645FD7FFA6FFE4EC723036D13CF984" authority="Evans and Sigogneau" authorityName="Evans and Sigogneau" box="[810,1309,1567,1591]" class="Amphibia" genus="Rubricacaecilia" higherTaxonomySource="GBIF" kingdom="Animalia" order="Gymnophiona" pageId="11" pageNumber="12" phylum="Chordata" rank="species" species="monbaroni">
<emphasis id="B910F846FFA6FFE4EC723036D012F984" box="[810,1075,1567,1591]" italics="true" pageId="11" pageNumber="12">Rubricacaecilia monbaroni</emphasis>
Evans and Sigogneau
</taxonomicName>
-Russell 2001, and Oligocene
<taxonomicName id="4C645FD7FFA6FFE4EC9B3017D04AF9E5" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[963,1131,1598,1622]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="11" pageNumber="12" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFA6FFE4EC9B3017D04AF9E5" box="[963,1131,1598,1622]" italics="true" pageId="11" pageNumber="12">Ymboirana acrux</emphasis>
</taxonomicName>
represent the only named fossils of gymnophionomorphs with preserved skulls and postcranial elements known so far. Based on the anatomical comparisons detailed below, we conclude that
<taxonomicName id="4C645FD7FFA6FFE4EBCB30B5D160F907" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1171,1345,1692,1716]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="11" pageNumber="12" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFA6FFE4EBCB30B5D160F907" box="[1171,1345,1692,1716]" italics="true" pageId="11" pageNumber="12">Ymboirana acrux</emphasis>
</taxonomicName>
should be considered a member of
<taxonomicName id="4C645FD7FFA6FFE4EB6C3092D0F4F960" authorityName="Taylor" authorityYear="1968" box="[1076,1237,1723,1747]" class="Amphibia" family="Typhlonectidae" kingdom="Animalia" order="Gymnophiona" pageId="11" pageNumber="12" phylum="Chordata" rank="family">Typhlonectidae</taxonomicName>
and is thus the only taxon among the aforementioned fossil species belonging to crown group
<taxonomicName id="4C645FD7FFA6FFE4ECE930D3D06BF8A1" authorityName="Rafinesque" authorityYear="1814" box="[945,1098,1786,1810]" class="Amphibia" kingdom="Animalia" order="Gymnophiona" pageId="11" pageNumber="12" phylum="Chordata" rank="order">Gymnophiona</taxonomicName>
.
</paragraph>
<paragraph id="8BDB2454FFA6FFE4EB7E3118D096F8F8" blockId="11.[810,1459,1841,1967]" box="[1062,1207,1841,1868]" pageId="11" pageNumber="12">
<emphasis id="B910F846FFA6FFE4EB7E3118D096F8F8" bold="true" box="[1062,1207,1841,1868]" pageId="11" pageNumber="12">The skull roof</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA6FFE1EC723171D637FD8C" blockId="11.[810,1459,1841,1967]" lastBlockId="14.[128,778,144,1390]" lastPageId="14" lastPageNumber="15" pageId="11" pageNumber="12">
A major variation in caecilian skulls is the presence or ab - sence of distinct upper temporal fenestrae: conditions termed zygokrotaphy and stegokrotaphy, respectively (
<figureCitation id="135F38D1FFA6FFE4EA5831BED166F81C" box="[1280,1351,1943,1967]" captionStart="Figure 10" captionStartId="12.[129,194,1836,1860]" captionTargetBox="[293,1309,144,1808]" captionTargetId="figure-5@12.[293,1309,144,1808]" captionTargetPageId="12" captionText="Figure 10. Caecilian skulls in dorsal view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333169" httpUri="https://zenodo.org/record/14333169/files/figure.png" pageId="11" pageNumber="12">Figs 10</figureCitation>
,
<figureCitation id="135F38D1FFA6FFE4EA0831BED14BF81C" box="[1360,1386,1943,1967]" captionStart="Figure 11" captionStartId="13.[113,178,1836,1860]" captionTargetBox="[278,1294,144,1808]" captionTargetId="figure-8@13.[278,1294,144,1808]" captionTargetPageId="13" captionText="Figure 11. Caecilian skulls in lateral view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333171" httpUri="https://zenodo.org/record/14333171/files/figure.png" pageId="11" pageNumber="12">11</figureCitation>
). Most modern caecilians are more stegokrotaphic than zygokrotaphic, with at most a very narrow temporal gap between parietals and squamosals (
<figureCitation id="135F38D1FFA3FFE1EE5136E6D546FF54" box="[265,359,207,231]" captionStart="Figure 10" captionStartId="12.[129,194,1836,1860]" captionTargetBox="[293,1309,144,1808]" captionTargetId="figure-5@12.[293,1309,144,1808]" captionTargetPageId="12" captionText="Figure 10. Caecilian skulls in dorsal view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333169" httpUri="https://zenodo.org/record/14333169/files/figure.png" pageId="14" pageNumber="15">Figs 10A</figureCitation>
,
<figureCitation id="135F38D1FFA3FFE1EE2E36E6D580FF54" box="[374,417,207,231]" captionStart="Figure 11" captionStartId="13.[113,178,1836,1860]" captionTargetBox="[278,1294,144,1808]" captionTargetId="figure-8@13.[278,1294,144,1808]" captionTargetPageId="13" captionText="Figure 11. Caecilian skulls in lateral view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333171" httpUri="https://zenodo.org/record/14333171/files/figure.png" pageId="14" pageNumber="15">11A</figureCitation>
). In zygokrotaphic rhinatrematids (
<figureCitation id="135F38D1FFA3FFE1EFD336C7D4C5FEB5" box="[139,228,238,262]" captionStart="Figure 10" captionStartId="12.[129,194,1836,1860]" captionTargetBox="[293,1309,144,1808]" captionTargetId="figure-5@12.[293,1309,144,1808]" captionTargetPageId="12" captionText="Figure 10. Caecilian skulls in dorsal view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333169" httpUri="https://zenodo.org/record/14333169/files/figure.png" pageId="14" pageNumber="15">Figs 10B</figureCitation>
,
<figureCitation id="135F38D1FFA3FFE1EFA836C7D539FEB5" box="[240,280,238,262]" captionStart="Figure 11" captionStartId="13.[113,178,1836,1860]" captionTargetBox="[278,1294,144,1808]" captionTargetId="figure-8@13.[278,1294,144,1808]" captionTargetPageId="13" captionText="Figure 11. Caecilian skulls in lateral view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333171" httpUri="https://zenodo.org/record/14333171/files/figure.png" pageId="14" pageNumber="15">11B</figureCitation>
), the ancestral jaw -closing muscles pass through the temporal fenestra and extend to the sagittal crest at the mid - line of the skull roof. In the other strongly zygokrotaphic caecil - ians, the jaw -closing muscles do not pass through the temporal fenestra or extend on to the skull roof (
<figureCitation id="135F38D1FFA3FFE1EEA53742D674FE30" box="[509,597,363,387]" captionStart="Figure 10" captionStartId="12.[129,194,1836,1860]" captionTargetBox="[293,1309,144,1808]" captionTargetId="figure-5@12.[293,1309,144,1808]" captionTargetPageId="12" captionText="Figure 10. Caecilian skulls in dorsal view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333169" httpUri="https://zenodo.org/record/14333169/files/figure.png" pageId="14" pageNumber="15">Figs10C</figureCitation>
,
<figureCitation id="135F38D1FFA3FFE1ED063742D6ABFE30" box="[606,650,363,387]" captionStart="Figure 11" captionStartId="13.[113,178,1836,1860]" captionTargetBox="[278,1294,144,1808]" captionTargetId="figure-8@13.[278,1294,144,1808]" captionTargetPageId="13" captionText="Figure 11. Caecilian skulls in lateral view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333171" httpUri="https://zenodo.org/record/14333171/files/figure.png" pageId="14" pageNumber="15">11C</figureCitation>
; Supporting Information,
<figureCitation id="135F38D1FFA3FFE1EE5237A2D574FE10" box="[266,341,395,419]" captionStart="Figure 3" captionStartId="4.[129,194,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-140@4.[129,1473,144,1600]" captionTargetPageId="4" captionText="Figure 3. CT-scans of the two skull parts of Ymboirana acrux gen. et sp. nov. Top part in dorsal (A) and ventral (B) views. Bottom part in dorsal (C) and ventral (D) views. See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333149" httpUri="https://zenodo.org/record/14333149/files/figure.png" pageId="14" pageNumber="15">Figs S3</figureCitation>
, S
<figureCitation id="135F38D1FFA3FFE1EE2837A2D55CFE10" box="[368,381,395,419]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="14" pageNumber="15">4</figureCitation>
). Rhinatrematid zygokrotaphy is con - sidered primary (ancestral for caecilians, see:
<bibRefCitation id="EFF559A5FFA3FFE1ED0E3783D6DFFE71" author="Nussbaum RA" box="[598,766,426,450]" pageId="14" pageNumber="15" pagination="1 - 30" refId="ref12648" refString="Nussbaum RA. Rhinatrematidae: a new family of caecilians (Amphibia: Gymnophiona). Occasional Papers of the Museum of Zoologo, Universito of Michigan 1977; 682: 1 - 30." type="journal article" year="1977">Nussbaum 1977</bibRefCitation>
) with zygokrotaphy in other caecilians (i.e. typhlonectids,
<taxonomicName id="4C645FD7FFA3FFE1EFD937C0D53DFDB2" box="[129,284,489,513]" class="Amphibia" family="Scolecomorphidae" genus="Scolecomorphus" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EFD937C0D53DFDB2" box="[129,284,489,513]" italics="true" pageId="14" pageNumber="15">Scolecomorphus</emphasis>
</taxonomicName>
, and
<emphasis id="B910F846FFA3FFE1EE0437C0D5EFFDB3" box="[348,462,489,512]" italics="true" pageId="14" pageNumber="15">Geotrypetes</emphasis>
) secondary and having inde - pendently evolved at least three times (e.g.
<bibRefCitation id="EFF559A5FFA3FFE1ED003421D725FD93" author="Nussbaum RA" box="[600,772,520,544]" pageId="14" pageNumber="15" pagination="1 - 30" refId="ref12648" refString="Nussbaum RA. Rhinatrematidae: a new family of caecilians (Amphibia: Gymnophiona). Occasional Papers of the Museum of Zoologo, Universito of Michigan 1977; 682: 1 - 30." type="journal article" year="1977">Nussbaum 1977</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFA3FFE1EFD9340ED505FD8C" author="Wilkinson M" box="[129,292,551,575]" pageId="14" pageNumber="15" pagination="423 - 70" refId="ref13967" refString="Wilkinson M. Characters, congruence and quality: a study of neuroana * tomical and traditional data in caecilian phylogeny. Biological Reviews 1997; 72: 423 - 70. https: // doi. org / 10.1111 / j. 1469 * 185 x. 1997. tb 00020. x" type="journal article" year="1997">Wilkinson 1997</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFA3FFE1EE77340ED624FD8C" author="Kleinteich T &amp; Maddin HC &amp; Herzen J" box="[303,517,551,575]" pageId="14" pageNumber="15" pagination="833 - 44" refId="ref12019" refString="Kleinteich T, Maddin HC, Herzen J et al. Is solid always best? Cranial performance in solid and fenestrated caecilian skulls. Ne Journal of Experimental Biologo 2012; 215: 833 - 44. https: // doi. org / 10.1242 / jeb. 065979" type="journal article" year="2012">
Kleinteich
<emphasis id="B910F846FFA3FFE1EEC63401D5ECFD8C" box="[414,461,551,575]" italics="true" pageId="14" pageNumber="15">et al.</emphasis>
2012
</bibRefCitation>
).
</paragraph>
<caption id="DF1B74DCFFA1FFE3EFD93105D678F8CF" ID-DOI="http://doi.org/10.5281/zenodo.14333169" ID-Zenodo-Dep="14333169" httpUri="https://zenodo.org/record/14333169/files/figure.png" pageId="12" pageNumber="13" startId="12.[129,194,1836,1860]" targetBox="[293,1309,144,1808]" targetPageId="12" targetType="figure">
<paragraph id="8BDB2454FFA1FFE3EFD93105D678F8CF" blockId="12.[129,1428,1836,1916]" pageId="12" pageNumber="13">
<emphasis id="B910F846FFA1FFE3EFD93105D4C4F8F7" bold="true" box="[129,229,1836,1860]" pageId="12" pageNumber="13">Figure 10.</emphasis>
Caecilian skulls in dorsal view. Skull of
<taxonomicName id="4C645FD7FFA1FFE3ED003105D72DF8F7" authorityName="Boettger" authorityYear="1892" box="[600,780,1836,1860]" class="Amphibia" family="Siphonopidae" genus="Siphonops" kingdom="Animalia" order="Gymnophiona" pageId="12" pageNumber="13" phylum="Chordata" rank="species" species="paulensis">
<emphasis id="B910F846FFA1FFE3ED003105D72DF8F7" box="[600,780,1836,1860]" italics="true" pageId="12" pageNumber="13">Siphonops paulensis</emphasis>
</taxonomicName>
(A). Skull of
<taxonomicName id="4C645FD7FFA1FFE3ECD23105D078F8F7" baseAuthorityName="Guérin-Méneville" baseAuthorityYear="1838" box="[906,1113,1836,1860]" class="Amphibia" family="Rhinatrematidae" genus="Rhinatrema" kingdom="Animalia" order="Gymnophiona" pageId="12" pageNumber="13" phylum="Chordata" rank="species" species="bivitatum">
<emphasis id="B910F846FFA1FFE3ECD23105D078F8F7" box="[906,1113,1836,1860]" italics="true" pageId="12" pageNumber="13">Rhinatrema bivittatum</emphasis>
</taxonomicName>
(B). Skull of
<taxonomicName id="4C645FD7FFA1FFE3EB8D3105D4D0F8D3" baseAuthorityName="Reinhardt &amp; Lutken" baseAuthorityYear="1862" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="12" pageNumber="13" phylum="Chordata" rank="species" species="indistinctum">
<emphasis id="B910F846FFA1FFE3EB8D3105D4D0F8D3" italics="true" pageId="12" pageNumber="13">Chthonerpeton indistinctum</emphasis>
</taxonomicName>
(C). Interpretive line drawing of
<taxonomicName id="4C645FD7FFA1FFE3ED723161D6E7F8D3" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[554,710,1864,1888]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="12" pageNumber="13" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFA1FFE3ED723161D6E7F8D3" box="[554,710,1864,1888]" italics="true" pageId="12" pageNumber="13">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFA1FFE3ED923160D772F8D3" box="[714,851,1865,1889]" pageId="12" pageNumber="13" rank="species">gen. et sp. nov.</taxonomicNameLabel>
skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz.
</paragraph>
</caption>
<caption id="DF1B74DCFFA0FFE2EF293105D66BF8CF" ID-DOI="http://doi.org/10.5281/zenodo.14333171" ID-Zenodo-Dep="14333171" httpUri="https://zenodo.org/record/14333171/files/figure.png" pageId="13" pageNumber="14" startId="13.[113,178,1836,1860]" targetBox="[278,1294,144,1808]" targetPageId="13" targetType="figure">
<paragraph id="8BDB2454FFA0FFE2EF293105D66BF8CF" blockId="13.[113,1413,1836,1916]" pageId="13" pageNumber="14">
<emphasis id="B910F846FFA0FFE2EF293105D4F7F8F7" bold="true" box="[113,214,1836,1860]" pageId="13" pageNumber="14">Figure 11.</emphasis>
Caecilian skulls in lateral view. Skull of
<taxonomicName id="4C645FD7FFA0FFE2ED103105D6DDF8F7" authorityName="Boettger" authorityYear="1892" box="[584,764,1836,1860]" class="Amphibia" family="Siphonopidae" genus="Siphonops" kingdom="Animalia" order="Gymnophiona" pageId="13" pageNumber="14" phylum="Chordata" rank="species" species="paulensis">
<emphasis id="B910F846FFA0FFE2ED103105D6DDF8F7" box="[584,764,1836,1860]" italics="true" pageId="13" pageNumber="14">Siphonops paulensis</emphasis>
</taxonomicName>
(A). Skull of
<taxonomicName id="4C645FD7FFA0FFE2EC223105D068F8F7" baseAuthorityName="Guérin-Méneville" baseAuthorityYear="1838" box="[890,1097,1836,1860]" class="Amphibia" family="Rhinatrematidae" genus="Rhinatrema" kingdom="Animalia" order="Gymnophiona" pageId="13" pageNumber="14" phylum="Chordata" rank="species" species="bivitatum">
<emphasis id="B910F846FFA0FFE2EC223105D068F8F7" box="[890,1097,1836,1860]" italics="true" pageId="13" pageNumber="14">Rhinatrema bivittatum</emphasis>
</taxonomicName>
(B). Skull of
<taxonomicName id="4C645FD7FFA0FFE2EB9E3105D4C0F8D3" baseAuthorityName="Reinhardt &amp; Lutken" baseAuthorityYear="1862" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="13" pageNumber="14" phylum="Chordata" rank="species" species="indistinctum">
<emphasis id="B910F846FFA0FFE2EB9E3105D4C0F8D3" italics="true" pageId="13" pageNumber="14">Chthonerpeton indistinctum</emphasis>
</taxonomicName>
(C). Interpretive line drawing of
<taxonomicName id="4C645FD7FFA0FFE2ED433161D696F8D3" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[539,695,1864,1888]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="13" pageNumber="14" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFA0FFE2ED433161D696F8D3" box="[539,695,1864,1888]" italics="true" pageId="13" pageNumber="14">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFA0FFE2EDE33160D765F8D3" box="[699,836,1865,1889]" pageId="13" pageNumber="14" rank="species">gen. et sp. nov.</taxonomicNameLabel>
skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz.
</paragraph>
</caption>
<paragraph id="8BDB2454FFA3FFE1EFC4346ED65DFBA6" blockId="14.[128,778,144,1390]" pageId="14" pageNumber="15">
The fragmentary condition of the skull of the unique spe - cimen of
<taxonomicName id="4C645FD7FFA3FFE1EFBE344FD570FDCD" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[230,337,614,638]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EFBE344FD570FDCD" box="[230,337,614,638]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
, particularly the poor preservation of the squamosals, precludes determination of whether
<taxonomicName id="4C645FD7FFA3FFE1ED2B34ACD6FFFD2E" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[627,734,645,669]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1ED2B34ACD6FFFD2E" box="[627,734,645,669]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
was stegokraphic or zygokrotaphic. Well -developed sagittal crests on the parietals, a feature typically associated with primarily zygokrotaphic skulls (
<bibRefCitation id="EFF559A5FFA3FFE1EE3D34CAD62FFD48" author="Nussbaum RA" box="[357,526,739,763]" pageId="14" pageNumber="15" pagination="1 - 30" refId="ref12648" refString="Nussbaum RA. Rhinatrematidae: a new family of caecilians (Amphibia: Gymnophiona). Occasional Papers of the Museum of Zoologo, Universito of Michigan 1977; 682: 1 - 30." type="journal article" year="1977">Nussbaum 1977</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFA3FFE1ED4334CAD6D8FD48" author="Wilkinson M &amp; Reynolds RP &amp; Jacobs JF" box="[539,761,739,763]" pageId="14" pageNumber="15" pagination="27 - 34" refId="ref14314" refString="Wilkinson M, Reynolds RP, Jacobs JF. A new genus and species of rhinatrematid caecilian (Amphibia: Gymnophiona: Rhinatrematidae) from Ecuador. Herpetological Journal 2021; 31: 27 - 34." type="journal article" year="2021">
Wilkinson
<emphasis id="B910F846FFA3FFE1EDD534CDD69FFD48" box="[653,702,739,763]" italics="true" pageId="14" pageNumber="15">et al.</emphasis>
2021
</bibRefCitation>
), are not present in
<taxonomicName id="4C645FD7FFA3FFE1EE6F352BD583FCA9" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[311,418,770,794]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EE6F352BD583FCA9" box="[311,418,770,794]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
, and the parietals are not expanded laterally as in the secondarily stegokrotaphic
<taxonomicName id="4C645FD7FFA3FFE1ED2B350BD560FCEA" authority="(Nussbaum 1985)" baseAuthorityName="Nussbaum" baseAuthorityYear="1985" class="Amphibia" family="Scolecomorphidae" genus="Crotaphatrema" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1ED2B350BD728FC89" box="[627,777,802,826]" italics="true" pageId="14" pageNumber="15">Crotaphatrema</emphasis>
(
<bibRefCitation id="EFF559A5FFA3FFE1EFD33568D517FCEA" author="Nussbaum RA" box="[139,310,833,857]" pageId="14" pageNumber="15" pagination="1 - 49" refId="ref12741" refString="Nussbaum RA. Systematics of caecilians (Amphibia: Gymnophiona) of the family Scolecomorphidae. Occasional Papers of the Museum of Zoologo, Universito of Michigan 1985; 713: 1 - 49." type="journal article" year="1985">Nussbaum 1985</bibRefCitation>
)
</taxonomicName>
, but it is not possible to rule out primary stegokrotaphy or secondary zygokrotaphy based solely on the morphology of the parietals. The parietals of
<taxonomicName id="4C645FD7FFA3FFE1ED0E35A9D6E0FC2B" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[598,705,896,920]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1ED0E35A9D6E0FC2B" box="[598,705,896,920]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
have a median flattened portion and a lateral ventrally sloping region (
<figureCitation id="135F38D1FFA3FFE1EFD33597D4C5FC64" box="[139,228,958,983]" captionStart="Figure 12" captionStartId="15.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-115@15.[114,1458,144,1600]" captionTargetPageId="15" captionText="Figure 12. Paired parietals of four different caecilian species, all in dorsal view.Ymboirana acrux gen.et sp. nov.(A), Rhinatrema bivitatum (B), Tophlonectes natans (C), and Herpele squalostoma (D). See Appendix for abbreviations. Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333177" httpUri="https://zenodo.org/record/14333177/files/figure.png" pageId="14" pageNumber="15">Fig. 12A</figureCitation>
), which resembles secondarily zygokrotaphic caecil - ians (e.g. typhlonectids and scolecomorphids) but is also found in some more stegokrotaphic taxa (e.g. caeciliids).
</paragraph>
<paragraph id="8BDB2454FFA3FFE1EFC43235D622FADD" blockId="14.[128,778,144,1390]" pageId="14" pageNumber="15">
Compared with typhlonectids, the parietal shape in
<taxonomicName id="4C645FD7FFA3FFE1EFD83215D4CAFBE7" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[128,235,1084,1108]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EFD83215D4CAFBE7" box="[128,235,1084,1108]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
is very similar to
<taxonomicName id="4C645FD7FFA3FFE1EEE43215D66CFBE7" authorityName="Peters" authorityYear="1879" box="[444,589,1084,1108]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EEE43215D66CFBE7" box="[444,589,1084,1108]" italics="true" pageId="14" pageNumber="15">Chthonerpeton</emphasis>
</taxonomicName>
and
<taxonomicName id="4C645FD7FFA3FFE1EDD33215D72BFBE7" authorityName="Taylor" authorityYear="1968" box="[651,778,1084,1108]" class="Amphibia" family="Typhlonectidae" genus="Nectocaecilia" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EDD33215D72BFBE7" box="[651,778,1084,1108]" italics="true" pageId="14" pageNumber="15">Nectocaecilia</emphasis>
</taxonomicName>
(
<figureCitation id="135F38D1FFA3FFE1EFD33272D4CBFBC0" box="[139,234,1115,1139]" captionStart="Figure 10" captionStartId="12.[129,194,1836,1860]" captionTargetBox="[293,1309,144,1808]" captionTargetId="figure-5@12.[293,1309,144,1808]" captionTargetPageId="12" captionText="Figure 10. Caecilian skulls in dorsal view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333169" httpUri="https://zenodo.org/record/14333169/files/figure.png" pageId="14" pageNumber="15">Figs 10C</figureCitation>
,
<figureCitation id="135F38D1FFA3FFE1EFA13272D504FBC0" box="[249,293,1115,1139]" captionStart="Figure 11" captionStartId="13.[113,178,1836,1860]" captionTargetBox="[278,1294,144,1808]" captionTargetId="figure-8@13.[278,1294,144,1808]" captionTargetPageId="13" captionText="Figure 11. Caecilian skulls in lateral view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333171" httpUri="https://zenodo.org/record/14333171/files/figure.png" pageId="14" pageNumber="15">11C</figureCitation>
; Supporting Information,
<figureCitation id="135F38D1FFA3FFE1ED183272D69BFBC0" box="[576,698,1115,1139]" captionStart="Figure 3" captionStartId="4.[129,194,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-140@4.[129,1473,144,1600]" captionTargetPageId="4" captionText="Figure 3. CT-scans of the two skull parts of Ymboirana acrux gen. et sp. nov. Top part in dorsal (A) and ventral (B) views. Bottom part in dorsal (C) and ventral (D) views. See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333149" httpUri="https://zenodo.org/record/14333149/files/figure.png" pageId="14" pageNumber="15">Figs S3A, S</figureCitation>
<figureCitation id="135F38D1FFA3FFE1EDE23272D6F8FBC0" box="[698,729,1115,1139]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="14" pageNumber="15">4A</figureCitation>
) re - garding the degree of ventral sloping, whereas in
<taxonomicName id="4C645FD7FFA3FFE1ED2F3253D49FFB01" baseAuthorityName="Berthold" baseAuthorityYear="1859" class="Amphibia" family="Typhlonectidae" genus="Potomotophlus" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="species" species="kaupii">
<emphasis id="B910F846FFA3FFE1ED2F3253D49FFB01" italics="true" pageId="14" pageNumber="15">Potomotyphlus kaupii</emphasis>
</taxonomicName>
and
<emphasis id="B910F846FFA3FFE1EFAC32B3D550FB01" box="[244,369,1178,1202]" italics="true" pageId="14" pageNumber="15">Typhlonectes</emphasis>
(Supporting Information,
<figureCitation id="135F38D1FFA3FFE1EDD132B3D4ACFB62" captionStart="Figure 3" captionStartId="4.[129,194,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-140@4.[129,1473,144,1600]" captionTargetPageId="4" captionText="Figure 3. CT-scans of the two skull parts of Ymboirana acrux gen. et sp. nov. Top part in dorsal (A) and ventral (B) views. Bottom part in dorsal (C) and ventral (D) views. See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333149" httpUri="https://zenodo.org/record/14333149/files/figure.png" pageId="14" pageNumber="15">Figs S3B, C, S</figureCitation>
<figureCitation id="135F38D1FFA3FFE1EFD53290D4E7FB62" box="[141,198,1209,1233]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="14" pageNumber="15">4B, C</figureCitation>
) the slope is less -pronounced and in
<taxonomicName id="4C645FD7FFA3FFE1ED623290D6D7FB62" baseAuthorityName="Taylor" baseAuthorityYear="1968" box="[570,758,1209,1233]" class="Amphibia" family="Typhlonectidae" genus="Atretochoana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="species" species="eiselti">
<emphasis id="B910F846FFA3FFE1ED623290D6D7FB62" box="[570,758,1209,1233]" italics="true" pageId="14" pageNumber="15">Atretochoana eiselti</emphasis>
</taxonomicName>
it is completely absent (
<bibRefCitation id="EFF559A5FFA3FFE1EE3932F1D685FB43" author="Wilkinson M &amp; Nussbaum RA" box="[353,676,1240,1264]" pageId="14" pageNumber="15" pagination="39 - 109" refId="ref14053" refString="Wilkinson M, Nussbaum RA. Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae). Biological Journal of the Linnean Societo 1997; 62: 39 - 109. https: // doi. org / 10.1111 / j. 1095 * 8312.1997. tb 01616. x" type="journal article" year="1997">Wilkinson and Nussbaum 1997</bibRefCitation>
). Despite the uncertainty with respect to the skull roof shape of
<taxonomicName id="4C645FD7FFA3FFE1EDC132D1D725FAA3" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[665,772,1272,1296]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EDC132D1D725FAA3" box="[665,772,1272,1296]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
, its parietal morphology allows us to rule out putative taxonomic affinities with rhinatrematids and is at least consistent with the morphology present in typhlonectids.
</paragraph>
<paragraph id="8BDB2454FFA3FFE1EFF433A4D6FFFA14" blockId="14.[129,778,1421,1985]" box="[172,734,1421,1448]" pageId="14" pageNumber="15">
<emphasis id="B910F846FFA3FFE1EFF433A4D6FFFA14" bold="true" box="[172,734,1421,1448]" pageId="14" pageNumber="15">Maxillopalatines, nasopremaxillae, and septomaxillae</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA3FFE1EFD9339DD5DFF872" blockId="14.[129,778,1421,1985]" pageId="14" pageNumber="15">
The anterior portion of the skull is severely damaged making the identification of nasopremaxillae and maxillopalatines tentative and based mainly on their positions and the presence of tooth pedi - cels. In our reconstruction of the fossil skull (
<figureCitation id="135F38D1FFA3FFE1ED1D303BD6BEF999" box="[581,671,1554,1578]" captionStart="Figure 10" captionStartId="12.[129,194,1836,1860]" captionTargetBox="[293,1309,144,1808]" captionTargetId="figure-5@12.[293,1309,144,1808]" captionTargetPageId="12" captionText="Figure 10. Caecilian skulls in dorsal view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333169" httpUri="https://zenodo.org/record/14333169/files/figure.png" pageId="14" pageNumber="15">Figs 10D</figureCitation>
,
<figureCitation id="135F38D1FFA3FFE1EDF3303BD6F7F999" box="[683,726,1554,1578]" captionStart="Figure 11" captionStartId="13.[113,178,1836,1860]" captionTargetBox="[278,1294,144,1808]" captionTargetId="figure-8@13.[278,1294,144,1808]" captionTargetPageId="13" captionText="Figure 11. Caecilian skulls in lateral view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333171" httpUri="https://zenodo.org/record/14333171/files/figure.png" pageId="14" pageNumber="15">11D</figureCitation>
), we also assume that there is no separate septomaxillae in the snout.One could argue that there is no evidence for the lack of septomaxillae in
<taxonomicName id="4C645FD7FFA3FFE1EFC03059D4DEF93B" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[152,255,1648,1672]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EFC03059D4DEF93B" box="[152,255,1648,1672]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
, as well as for the fusion of maxillae with the palatines, and the nasals with the premaxillae. However, in all adult modern caecilians the maxillae are fused to the palatines (e.g.
<bibRefCitation id="EFF559A5FFA3FFE1EDDB3086D6D8F974" author="Taylor EH" box="[643,761,1711,1735]" pageId="14" pageNumber="15" pagination="585 - 687" refId="ref13586" refString="Taylor EH. Skulls of Gymnophiona and their significance in the tax * onomy of the group. Ne Universito of Kansas Science Bulletin 1969; 48: 585 - 687." type="journal article" year="1969">Taylor 1969</bibRefCitation>
), and separate nasals, premaxillae, and septomaxillae are known ex - clusively in rhinatrematids, ichthyophiids, scolecomorphids, and, with the exception of the septomaxillae, in
<taxonomicName id="4C645FD7FFA3FFE1ED1C3124D6ACF896" authorityName="Peters" authorityYear="1880" box="[580,653,1805,1829]" class="Amphibia" family="Herpelidae" genus="Herpele" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1ED1C3124D6ACF896" box="[580,653,1805,1829]" italics="true" pageId="14" pageNumber="15">Herpele</emphasis>
</taxonomicName>
(e.g.
<bibRefCitation id="EFF559A5FFA3FFE1ED913124D492F8F7" author="Taylor EH" pageId="14" pageNumber="15" pagination="585 - 687" refId="ref13586" refString="Taylor EH. Skulls of Gymnophiona and their significance in the tax * onomy of the group. Ne Universito of Kansas Science Bulletin 1969; 48: 585 - 687." type="journal article" year="1969">Taylor 1969</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFA3FFE1EF983105D555F8F7" author="Muller H &amp; Oommen OV &amp; Bartsch P" box="[192,372,1836,1860]" pageId="14" pageNumber="15" pagination="171 - 88" refId="ref12532" refString="Muller H, Oommen OV, Bartsch P. Skeletal development of the direct * developing caecilian Gegeneophis ramaswamii (Amphibia: Gymnophiona: Caeciliidae). Zoomorphologo 2005; 124: 171 - 88. https: // doi. org / 10.1007 / s 00435 * 005 * 0005 * 6" type="journal article" year="2005">
Müller
<emphasis id="B910F846FFA3FFE1EE533104D51AF8F7" box="[267,315,1836,1860]" italics="true" pageId="14" pageNumber="15">et al.</emphasis>
2005
</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFA3FFE1EED93105D678F8F7" author="Wilkinson M &amp; San Mauro D &amp; Sherratt E" box="[385,601,1836,1860]" pageId="14" pageNumber="15" pagination="41 - 64" refId="ref14211" refString="Wilkinson M, San Mauro D, Sherratt E et al. A nine * family classification of caecilians (Amphibia: Gymnophiona). Zootaxa 2011; 2874: 41 - 64. https: // doi. org / 10.11646 / zootaxa. 2874.1.3" type="journal article" year="2011">
Wilkinson
<emphasis id="B910F846FFA3FFE1EEA83104D601F8F7" box="[496,544,1836,1860]" italics="true" pageId="14" pageNumber="15">et al.</emphasis>
2011
</bibRefCitation>
), which all differ from
<taxonomicName id="4C645FD7FFA3FFE1EFE33162D502F8D0" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[187,291,1867,1891]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EFE33162D502F8D0" box="[187,291,1867,1891]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
in several other respects (for more details, see Diagnosis). Thus, in the absence of evidence favouring the con - trary, we assume that
<taxonomicName id="4C645FD7FFA3FFE1EE0131A3D5E0F811" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[345,449,1930,1954]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EE0131A3D5E0F811" box="[345,449,1930,1954]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
exhibits the same skull configur - ation as all other known typhlonectids.
</paragraph>
<paragraph id="8BDB2454FFA3FFE1EB1E36B9D094FF19" blockId="14.[825,1475,144,1052]" box="[1094,1205,144,170]" pageId="14" pageNumber="15">
<emphasis id="B910F846FFA3FFE1EB1E36B9D094FF19" bold="true" box="[1094,1205,144,170]" pageId="14" pageNumber="15">Quadrates</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA3FFE1EC61369ED01DFBAF" blockId="14.[825,1475,144,1052]" pageId="14" pageNumber="15">
The quadrates of
<taxonomicName id="4C645FD7FFA3FFE1ECA4369FD046FF7D" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1020,1127,182,206]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1ECA4369FD046FF7D" box="[1020,1127,182,206]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
seem to lack distinct otic pro - cesses, as expected given the narrow and delicate morphology of the bone tentatively interpreted as the stapes. This condition is common among typhlonectids where, with the exception of
<taxonomicName id="4C645FD7FFA3FFE1EC0F371DD7C9FEFF" authorityName="Peters" authorityYear="1879" box="[855,1000,308,332]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EC0F371DD7C9FEFF" box="[855,1000,308,332]" italics="true" pageId="14" pageNumber="15">Chthonerpeton</emphasis>
</taxonomicName>
and
<taxonomicName id="4C645FD7FFA3FFE1EB7A371DD080FEFF" authorityName="Taylor" authorityYear="1968" box="[1058,1185,308,332]" class="Amphibia" family="Typhlonectidae" genus="Nectocaecilia" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EB7A371DD080FEFF" box="[1058,1185,308,332]" italics="true" pageId="14" pageNumber="15">Nectocaecilia</emphasis>
</taxonomicName>
, the otic process is limited to a faint bony projection or may even be completely absent (
<bibRefCitation id="EFF559A5FFA3FFE1EC1C375BD0B1FE39" author="Wilkinson M &amp; Nussbaum RA" box="[836,1168,370,394]" pageId="14" pageNumber="15" pagination="39 - 109" refId="ref14053" refString="Wilkinson M, Nussbaum RA. Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae). Biological Journal of the Linnean Societo 1997; 62: 39 - 109. https: // doi. org / 10.1111 / j. 1095 * 8312.1997. tb 01616. x" type="journal article" year="1997">Wilkinson and Nussbaum 1997</bibRefCitation>
). Another distinct preserved portion of the quadrates in
<taxonomicName id="4C645FD7FFA3FFE1EB3637BBD0F8FE19" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1134,1241,402,426]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EB3637BBD0F8FE19" box="[1134,1241,402,426]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
comprises the ptery - goid process. Caecilians vary in the form of articulation be - tween the quadrate and the maxillopalatine (
<bibRefCitation id="EFF559A5FFA3FFE1EA4437F9D1B3FE5B" author="Wake MH" box="[1308,1426,464,488]" pageId="14" pageNumber="15" pagination="1811 - 1878" refId="ref13776" refString="Wake MH. The osteology of caecilians. In: Heatwole H, Davies M (eds), Amphibian Biologo, Vol. 5. Osteologo. Chipping Norton: Surrey Beatty &amp; Sons, Pty. Ltd, 2003, 1811 - 1878." type="book chapter" year="2003">
<collectingCountry id="F37364C4FFA3FFE1EA4437F9D174FE5B" box="[1308,1365,464,488]" name="Wake Island" pageId="14" pageNumber="15">Wake</collectingCountry>
2003
</bibRefCitation>
). In rhinatrematids and ichthyophiids, these bones are separated ventrally by a large pterygoid, whereas in many teresomatan cae - cilians the quadrates bear a well -developed, anteriorly directed pterygoid process and there is a small bone, which has been variously named, that we interpret as a reduced pterygoid (for a review, see:
<bibRefCitation id="EFF559A5FFA3FFE1EC9F34A5D05DFD17" author="Muller H &amp; Oommen OV &amp; Bartsch P" box="[967,1148,652,676]" pageId="14" pageNumber="15" pagination="171 - 88" refId="ref12532" refString="Muller H, Oommen OV, Bartsch P. Skeletal development of the direct * developing caecilian Gegeneophis ramaswamii (Amphibia: Gymnophiona: Caeciliidae). Zoomorphologo 2005; 124: 171 - 88. https: // doi. org / 10.1007 / s 00435 * 005 * 0005 * 6" type="journal article" year="2005">
Müller
<emphasis id="B910F846FFA3FFE1EB4A34A4D063FD17" box="[1042,1090,652,676]" italics="true" pageId="14" pageNumber="15">et al.</emphasis>
2005
</bibRefCitation>
) that lies between, or lateral to, the pterygoid process of the quadrate and the maxillopalatine. In some other teresomatan caecilians, including typhlonectids, the pterygoid process of each quadrate is particularly well developed (at least in some cases incorporating an embryonic pterygoid; see:
<bibRefCitation id="EFF559A5FFA3FFE1EC323500D005FCF2" author="Ramaswami LS" box="[874,1060,809,833]" pageId="14" pageNumber="15" pagination="752 - 60" refId="ref12959" refString="Ramaswami LS. The chondrocranium of Gegenophis (Apoda, Amphibia). Proceedings of the Zoological Societo of London 1948; 118: 752 - 60. https: // doi. org / 10.1111 / j. 1096 * 3642.1948. tb 00404. x" type="journal article" year="1948">Ramaswami 1948</bibRefCitation>
), and there is no separate element be - tween the quadrate and the maxillopalatine in adults.
<taxonomicName id="4C645FD7FFA3FFE1EA0F3561D1E3FCD3" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1367,1474,840,864]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EA0F3561D1E3FCD3" box="[1367,1474,840,864]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
exhibits a large pterygoid process of the quadrate and there are no signs of an isolated bone between the quadrate and the pre - served portions of the maxillopalatine, which is consistent with typhlonectid morphology, although the damaged and fragmen - tary nature of the fossil necessarily limits confidence in the ab - sence of such an element.
</paragraph>
<paragraph id="8BDB2454FFA3FFE1EB03326ED081FBD2" blockId="14.[825,1474,1095,1628]" box="[1115,1184,1095,1121]" pageId="14" pageNumber="15">
<emphasis id="B910F846FFA3FFE1EB03326ED081FBD2" bold="true" box="[1115,1184,1095,1121]" pageId="14" pageNumber="15">Stapes</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA3FFE1EC613247D0ECF9EF" blockId="14.[825,1474,1095,1628]" pageId="14" pageNumber="15">
All caecilians, except adult scolecomorphids, have stapes (e.g.
<bibRefCitation id="EFF559A5FFA3FFE1EC6132A4D7C0FB16" author="Nussbaum RA" box="[825,993,1165,1189]" pageId="14" pageNumber="15" pagination="1 - 49" refId="ref12741" refString="Nussbaum RA. Systematics of caecilians (Amphibia: Gymnophiona) of the family Scolecomorphidae. Occasional Papers of the Museum of Zoologo, Universito of Michigan 1985; 713: 1 - 49." type="journal article" year="1985">Nussbaum 1985</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFA3FFE1ECB532A4D080FB16" author="Muller H &amp; Wilkinson M &amp; Loader SP" box="[1005,1185,1165,1189]" pageId="14" pageNumber="15" pagination="491 - 504" refId="ref12585" refString="Muller H, Wilkinson M, Loader SP et al. Morphology and func * tion of the head in foetal and juvenile Scolecomorphus kirkii (Amphibia: Gymnophiona: Scolecomorphidae). Biological Journal of the Linnean Societo 2009; 96: 491 - 504. https: // doi. org / 10.1111 / j. 1095 * 8312.2008.01152. x" type="journal article" year="2009">
Müller
<emphasis id="B910F846FFA3FFE1EB6032A7D049FB16" box="[1080,1128,1165,1189]" italics="true" pageId="14" pageNumber="15">et al.</emphasis>
2009
</bibRefCitation>
). Caecilian stapes comprise a typically broad footplate that fills the foramen ovalis and a nar - rower and elongate stapedial style that usually articulates with the otic process of the quadrate (e.g.
<bibRefCitation id="EFF559A5FFA3FFE1EBEF32C2D74CFA91" author="Wilkinson M &amp; Nussbaum RA" pageId="14" pageNumber="15" pagination="39 - 109" refId="ref14053" refString="Wilkinson M, Nussbaum RA. Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae). Biological Journal of the Linnean Societo 1997; 62: 39 - 109. https: // doi. org / 10.1111 / j. 1095 * 8312.1997. tb 01616. x" type="journal article" year="1997">Wilkinson and Nussbaum 1997</bibRefCitation>
). Caecilians vary in the presence or absence of a stapedial foramen (or groove) in the base of the stapedial style (
<figureCitation id="135F38D1FFA3FFE1EA333303D190FAF1" box="[1387,1457,1322,1346]" captionStart="Figure 13" captionStartId="16.[130,195,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-149@16.[129,1473,144,1600]" captionTargetPageId="16" captionText="Figure 13. Left stapes of six different caecilian species, all in lateral view.Fragment tentatively identified as the stapes of Ymboirana acrux gen. et sp.nov.(A), Potomotophlus kaupii (B), Tophlonectes natans (C), Caecilia sp. (D), Siphonops paulensis (E), and Rhinatrema bivitatum (F). See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333179" httpUri="https://zenodo.org/record/14333179/files/figure.png" pageId="14" pageNumber="15">Fig. 13</figureCitation>
), a feature present in rhinatrematids, ichthyophiids, chikilids, and most herpelids, but absent in all other taxa (e.g.
<bibRefCitation id="EFF559A5FFA3FFE1EA003341D784FA13" author="Wilkinson M &amp; San Mauro D &amp; Sherratt E" pageId="14" pageNumber="15" pagination="41 - 64" refId="ref14211" refString="Wilkinson M, San Mauro D, Sherratt E et al. A nine * family classification of caecilians (Amphibia: Gymnophiona). Zootaxa 2011; 2874: 41 - 64. https: // doi. org / 10.11646 / zootaxa. 2874.1.3" type="journal article" year="2011">
Wilkinson
<emphasis id="B910F846FFA3FFE1EC6133A1D74BFA13" box="[825,874,1416,1440]" italics="true" pageId="14" pageNumber="15">et al.</emphasis>
2011
</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFA3FFE1ECEA33A1D048FA13" author="Kamei RG &amp; San Mauro D &amp; Gower DJ" box="[946,1129,1416,1440]" pageId="14" pageNumber="15" pagination="2396 - 401" refId="ref11972" refString="Kamei RG, San Mauro D, Gower DJ et al. Discovery of a new family of am * phibians from northeast India with ancient links to Africa. Proceedings of the Rooal Societo B: Biological Sciences 2012; 279: 2396 - 401." type="journal article" year="2012">
Kamei
<emphasis id="B910F846FFA3FFE1ECA533A1D00FFA13" box="[1021,1070,1416,1440]" italics="true" pageId="14" pageNumber="15">et al.</emphasis>
2012
</bibRefCitation>
, personal observation). The frag - ment tentatively identified as the stapes in
<taxonomicName id="4C645FD7FFA3FFE1EA58338ED14AFA0C" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1280,1387,1447,1471]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EA58338ED14AFA0C" box="[1280,1387,1447,1471]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
is short and narrow, with no sign of a stapedial foramen. Compared to typhlonectids (
<figureCitation id="135F38D1FFA3FFE1EC8033CCD06AFA4D" box="[984,1099,1509,1534]" captionStart="Figure 13" captionStartId="16.[130,195,1627,1651]" captionTargetBox="[129,1473,144,1600]" captionTargetId="figure-149@16.[129,1473,144,1600]" captionTargetPageId="16" captionText="Figure 13. Left stapes of six different caecilian species, all in lateral view.Fragment tentatively identified as the stapes of Ymboirana acrux gen. et sp.nov.(A), Potomotophlus kaupii (B), Tophlonectes natans (C), Caecilia sp. (D), Siphonops paulensis (E), and Rhinatrema bivitatum (F). See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333179" httpUri="https://zenodo.org/record/14333179/files/figure.png" pageId="14" pageNumber="15">Fig. 13B, C</figureCitation>
), the stapes in
<taxonomicName id="4C645FD7FFA3FFE1EBB133CCD175FA4E" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1257,1364,1509,1533]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EBB133CCD175FA4E" box="[1257,1364,1509,1533]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
closely re - sembles the condition present in
<emphasis id="B910F846FFA3FFE1EBD7302CD100F9AE" box="[1167,1313,1541,1565]" italics="true" pageId="14" pageNumber="15">Potomotyphlus</emphasis>
, as in both taxa this element is limited to a short, rod -like style and a small foot - plate (
<bibRefCitation id="EFF559A5FFA3FFE1EC23306DD09DF9EF" author="Wilkinson M &amp; Nussbaum RA" box="[891,1212,1604,1628]" pageId="14" pageNumber="15" pagination="39 - 109" refId="ref14053" refString="Wilkinson M, Nussbaum RA. Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae). Biological Journal of the Linnean Societo 1997; 62: 39 - 109. https: // doi. org / 10.1111 / j. 1095 * 8312.1997. tb 01616. x" type="journal article" year="1997">Wilkinson and Nussbaum 1997</bibRefCitation>
).
</paragraph>
<paragraph id="8BDB2454FFA3FFE1EB1330ADD091F92D" blockId="14.[825,1475,1668,1981]" box="[1099,1200,1668,1694]" pageId="14" pageNumber="15">
<emphasis id="B910F846FFA3FFE1EB1330ADD091F92D" bold="true" box="[1099,1200,1668,1694]" pageId="14" pageNumber="15">Os basale</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA3FFE0EC613082D5FEF8AF" blockId="14.[825,1475,1668,1981]" lastBlockId="15.[113,762,1765,1820]" lastPageId="15" lastPageNumber="16" pageId="14" pageNumber="15">
The azygous os basale is a distinctive compound bone of cae - cilians that forms the posterior, posterolateral walls, and floor of the cranial cavity (
<bibRefCitation id="EFF559A5FFA3FFE1EB4430C0D103F8B2" author="Sarasin P &amp; Sarasin F" box="[1052,1314,1769,1793]" pageId="14" pageNumber="15" refId="ref13387" refString="Sarasin P, Sarasin F. Ergebnisse naturwissenschasslichen. Forschungen auf Ceolon in den Jahren 1884 - 1886. Zur Entwicklungsgeschichte und Anatomie der ceolonischen Blindwuhle Ichthoophis glutinosus. Wiesbaden: C. W. Kriedel's Verlag, 1890." type="book" year="1890">Sarasin and Sarasin 1890</bibRefCitation>
). This element includes the otic capsules and bears numerous processes (e.g. parasphenoid and basipterygoid processes) and foramina (e.g. foramen ovalis, jugular foramen, and antotic foramina; see:
<bibRefCitation id="EFF559A5FFA3FFE1EC61314FD7E6F8CD" author="Maddin HC" box="[825,967,1894,1918]" pageId="14" pageNumber="15" pagination="850 - 71" refId="ref12375" refString="Maddin HC. Deciphering morphological variation in the braincase of caecilian amphibians (Gymnophiona). Journal of Morphologo 2011; 272: 850 - 71. https: // doi. org / 10.1002 / jmor. 10953" type="journal article" year="2011">Maddin 2011</bibRefCitation>
). In the
<typeStatus id="54DF9AF6FFA3FFE1EB70314FD0A5F8CD" box="[1064,1156,1894,1918]" pageId="14" pageNumber="15" type="holotype">holotype</typeStatus>
of
<taxonomicName id="4C645FD7FFA3FFE1EBF1314FD135F8CD" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1193,1300,1894,1918]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="14" pageNumber="15" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA3FFE1EBF1314FD135F8CD" box="[1193,1300,1894,1918]" italics="true" pageId="14" pageNumber="15">Ymboirana</emphasis>
</taxonomicName>
, the os basale is represented by scattered fragments, few of which are sufficiently large to enable identification of features that might help inform the affinities of
<taxonomicName id="4C645FD7FFA2FFE0EE4E30CCD5A0F94E" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[278,385,1765,1789]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="15" pageNumber="16" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFA2FFE0EE4E30CCD5A0F94E" box="[278,385,1765,1789]" italics="true" pageId="15" pageNumber="16">Ymboirana</emphasis>
</taxonomicName>
, but a well -developed basipterygoid process places it within Teresomata.
</paragraph>
<caption id="DF1B74DCFFA2FFE0EF2B3075D06CF93C" ID-DOI="http://doi.org/10.5281/zenodo.14333177" ID-Zenodo-Dep="14333177" httpUri="https://zenodo.org/record/14333177/files/figure.png" pageId="15" pageNumber="16" startId="15.[115,180,1628,1652]" targetBox="[114,1458,144,1600]" targetPageId="15" targetType="figure">
<paragraph id="8BDB2454FFA2FFE0EF2B3075D06CF93C" blockId="15.[113,1450,1628,1680]" pageId="15" pageNumber="16">
<emphasis id="B910F846FFA2FFE0EF2B3075D4F6F9C7" bold="true" box="[115,215,1628,1652]" pageId="15" pageNumber="16">Figure 12.</emphasis>
Paired parietals of four different caecilian species, all in dorsal view.
<taxonomicName id="4C645FD7FFA2FFE0EC0D3075D7D0F9C7" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[853,1009,1628,1652]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="15" pageNumber="16" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFA2FFE0EC0D3075D7D0F9C7" box="[853,1009,1628,1652]" italics="true" pageId="15" pageNumber="16">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFA2FFE0ECAD3075D05EF9C0" box="[1013,1151,1628,1652]" pageId="15" pageNumber="16" rank="species">gen. et sp. nov.</taxonomicNameLabel>
(A),
<taxonomicName id="4C645FD7FFA2FFE0EBE83075D15EF9C7" baseAuthorityName="Guérin-Méneville" baseAuthorityYear="1838" box="[1200,1407,1628,1652]" class="Amphibia" family="Rhinatrematidae" genus="Rhinatrema" kingdom="Animalia" order="Gymnophiona" pageId="15" pageNumber="16" phylum="Chordata" rank="species" species="bivitatum">
<emphasis id="B910F846FFA2FFE0EBE83075D15EF9C7" box="[1200,1407,1628,1652]" italics="true" pageId="15" pageNumber="16">Rhinatrema bivittatum</emphasis>
</taxonomicName>
(B),
<taxonomicName id="4C645FD7FFA2FFE0EF293051D507F923" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" box="[113,294,1656,1680]" class="Amphibia" family="Typhlonectidae" genus="Tophlonectes" kingdom="Animalia" order="Gymnophiona" pageId="15" pageNumber="16" phylum="Chordata" rank="species" species="natans">
<emphasis id="B910F846FFA2FFE0EF293051D507F923" box="[113,294,1656,1680]" italics="true" pageId="15" pageNumber="16">Typhlonectes natans</emphasis>
</taxonomicName>
(C), and
<taxonomicName id="4C645FD7FFA2FFE0EED93051D61DF923" baseAuthorityName="Stutchbury" baseAuthorityYear="1836" box="[385,572,1656,1680]" class="Amphibia" family="Herpelidae" genus="Herpele" kingdom="Animalia" order="Gymnophiona" pageId="15" pageNumber="16" phylum="Chordata" rank="species" species="squalostoma">
<emphasis id="B910F846FFA2FFE0EED93051D61DF923" box="[385,572,1656,1680]" italics="true" pageId="15" pageNumber="16">Herpele squalostoma</emphasis>
</taxonomicName>
(D). See Appendix for abbreviations. Scale bar = 1 mm.
</paragraph>
</caption>
<paragraph id="8BDB2454FFA2FFE0EE223115D5D0F8E5" blockId="15.[113,763,1852,1977]" box="[378,497,1852,1878]" pageId="15" pageNumber="16">
<emphasis id="B910F846FFA2FFE0EE223115D5D0F8E5" bold="true" box="[378,497,1852,1878]" pageId="15" pageNumber="16">Lower jaws</emphasis>
</paragraph>
<paragraph id="8BDB2454FFA2FFFFEF29314BD5E1F881" blockId="15.[113,763,1852,1977]" lastBlockId="16.[129,778,1756,1999]" lastPageId="16" lastPageNumber="17" pageId="15" pageNumber="16">
Caecilian mandibles each have only two bones, named by
<bibRefCitation id="EFF559A5FFA2FFE0EF2931ABD511F829" author="Eifertinger L" box="[113,304,1922,1946]" pageId="15" pageNumber="16" pagination="534 - 52" refId="ref11513" refString="Eifertinger L. Die Entwicklung des knochernen Unterkiefers von Hypogeophis: Beitrag zur Kenntnis der Gymnophionen XX. Zeitschriss fur Anatomie und Entwicklungsgeschichte 1933; 101: 534 - 52. https: // doi. org / 10.1007 / bf 02118189" type="journal article" year="1933">Eifertinger (1933)</bibRefCitation>
: a toothed pseudodentary anteriorly and an adentigerous pseudangular posteriorly that articulates with the upper jaw and has a pronounced and distinctive retroarticular process (e.g.
<bibRefCitation id="EFF559A5FFA2FFE0ECE2312DD049F8AE" author="Nussbaum RA" box="[954,1128,1796,1821]" pageId="15" pageNumber="16" pagination="1 - 30" refId="ref12648" refString="Nussbaum RA. Rhinatrematidae: a new family of caecilians (Amphibia: Gymnophiona). Occasional Papers of the Museum of Zoologo, Universito of Michigan 1977; 682: 1 - 30." type="journal article" year="1977">Nussbaum 1977</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFA2FFE0EB21312CD08CF8AE" author="Nussbaum RA" box="[1145,1197,1797,1821]" pageId="15" pageNumber="16" pagination="545 - 54" refId="ref12683" refString="Nussbaum RA. The evolution of a unique dual jaw-closing mechanism in caecilians: (Amphibia: Gymnophiona) and its bearing on cae * cilian ancestry. Journal of Zoologo 1983; 199: 545 - 54. https: // doi. org / 10.1111 / j. 1469 * 7998.1983. tb 05105. x" type="journal article" year="1983">1983</bibRefCitation>
). The left pseudangular is one of the best -preserved bones of
<taxonomicName id="4C645FD7FFA2FFE0EB96310DD15DF88F" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1230,1404,1828,1852]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="15" pageNumber="16" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFA2FFE0EB96310DD15DF88F" box="[1230,1404,1828,1852]" italics="true" pageId="15" pageNumber="16">Ymboirana acrux</emphasis>
</taxonomicName>
, and is virtually complete, except for its anteriormost part. The retroarticular process is robust, posteriorly elongate, and re - curved, unlike the narrow, straight, and horizontal condition observed in rhinatrematids (
<bibRefCitation id="EFF559A5FFA2FFE0EB083188D0D6F80A" author="Nussbaum RA" box="[1104,1271,1953,1977]" pageId="15" pageNumber="16" pagination="1 - 30" refId="ref12648" refString="Nussbaum RA. Rhinatrematidae: a new family of caecilians (Amphibia: Gymnophiona). Occasional Papers of the Museum of Zoologo, Universito of Michigan 1977; 682: 1 - 30." type="journal article" year="1977">Nussbaum 1977</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFA2FFE0EA5B3188D116F80A" author="Nussbaum RA" box="[1283,1335,1953,1977]" pageId="15" pageNumber="16" pagination="545 - 54" refId="ref12683" refString="Nussbaum RA. The evolution of a unique dual jaw-closing mechanism in caecilians: (Amphibia: Gymnophiona) and its bearing on cae * cilian ancestry. Journal of Zoologo 1983; 199: 545 - 54. https: // doi. org / 10.1111 / j. 1469 * 7998.1983. tb 05105. x" type="journal article" year="1983">1983</bibRefCitation>
). A distinct processus internus, a feature common to almost all caecilians (except scolecomorphids;
<bibRefCitation id="EFF559A5FFBDFFFFEECC30D2D61FF8A0" author="Nussbaum RA" box="[404,574,1787,1811]" pageId="16" pageNumber="17" pagination="1 - 49" refId="ref12741" refString="Nussbaum RA. Systematics of caecilians (Amphibia: Gymnophiona) of the family Scolecomorphidae. Occasional Papers of the Museum of Zoologo, Universito of Michigan 1985; 713: 1 - 49." type="journal article" year="1985">Nussbaum 1985</bibRefCitation>
), is also present in the pseudangular of
<taxonomicName id="4C645FD7FFBDFFFFEE173133D59BF881" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[335,442,1818,1842]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBDFFFFEE173133D59BF881" box="[335,442,1818,1842]" italics="true" pageId="16" pageNumber="17">Ymboirana</emphasis>
</taxonomicName>
.
</paragraph>
<caption id="DF1B74DCFFBDFFFFEFDA3072D616F918" ID-DOI="http://doi.org/10.5281/zenodo.14333179" ID-Zenodo-Dep="14333179" httpUri="https://zenodo.org/record/14333179/files/figure.png" pageId="16" pageNumber="17" startId="16.[130,195,1627,1651]" targetBox="[129,1473,144,1600]" targetPageId="16" targetType="figure">
<paragraph id="8BDB2454FFBDFFFFEFDA3072D616F918" blockId="16.[129,1459,1627,1708]" pageId="16" pageNumber="17">
<emphasis id="B910F846FFBDFFFFEFDA3072D4C7F9C7" bold="true" box="[130,230,1627,1652]" pageId="16" pageNumber="17">Figure 13.</emphasis>
Left stapes of six different caecilian species, all in lateral view. Fragment tentatively identified as the stapes of
<taxonomicName id="4C645FD7FFBDFFFFEBBC3075D1A1F9C0" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1252,1408,1628,1652]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFBDFFFFEBBC3075D1A1F9C0" box="[1252,1408,1628,1652]" italics="true" pageId="16" pageNumber="17">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFBDFFFFEADC3075D4FFF93C" pageId="16" pageNumber="17" rank="species">gen. et sp. nov.</taxonomicNameLabel>
(A),
<taxonomicName id="4C645FD7FFBDFFFFEE573051D5F5F923" baseAuthorityName="Berthold" baseAuthorityYear="1859" box="[271,468,1656,1680]" class="Amphibia" family="Typhlonectidae" genus="Potomotophlus" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="species" species="kaupii">
<emphasis id="B910F846FFBDFFFFEE573051D5F5F923" box="[271,468,1656,1680]" italics="true" pageId="16" pageNumber="17">Potomotyphlus kaupii</emphasis>
</taxonomicName>
(B),
<taxonomicName id="4C645FD7FFBDFFFFED5D3051D698F93C" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" box="[517,697,1656,1680]" class="Amphibia" family="Typhlonectidae" genus="Tophlonectes" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="species" species="natans">
<emphasis id="B910F846FFBDFFFFED5D3051D698F93C" box="[517,697,1656,1680]" italics="true" pageId="16" pageNumber="17">Typhlonectes natans</emphasis>
</taxonomicName>
(C),
<taxonomicName id="4C645FD7FFBDFFFFEDB43051D775F93C" box="[748,852,1656,1680]" class="Amphibia" family="Caeciliidae" genus="Caecilia" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="species" species="undetermined">
<emphasis id="B910F846FFBDFFFFEDB43051D714F923" box="[748,821,1656,1680]" italics="true" pageId="16" pageNumber="17">Caecilia</emphasis>
sp.
</taxonomicName>
(D),
<taxonomicName id="4C645FD7FFBDFFFFECDF3051D01AF923" authorityName="Boettger" authorityYear="1892" box="[903,1083,1656,1680]" class="Amphibia" family="Siphonopidae" genus="Siphonops" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="species" species="paulensis">
<emphasis id="B910F846FFBDFFFFECDF3051D01AF923" box="[903,1083,1656,1680]" italics="true" pageId="16" pageNumber="17">Siphonops paulensis</emphasis>
</taxonomicName>
(E), and
<taxonomicName id="4C645FD7FFBDFFFFEBCB3051D143F923" baseAuthorityName="Guérin-Méneville" baseAuthorityYear="1838" box="[1171,1378,1656,1680]" class="Amphibia" family="Rhinatrematidae" genus="Rhinatrema" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="species" species="bivitatum">
<emphasis id="B910F846FFBDFFFFEBCB3051D143F923" box="[1171,1378,1656,1680]" italics="true" pageId="16" pageNumber="17">Rhinatrema bivittatum</emphasis>
</taxonomicName>
(F). See Appendix for abbreviations. Scale bar = 1 mm.
</paragraph>
</caption>
<paragraph id="8BDB2454FFBDFFFFEFC43113D152F823" blockId="16.[129,778,1756,1999]" lastBlockId="16.[825,1475,1755,1999]" pageId="16" pageNumber="17">
The orientation of the posterior end of the retroarticular process is variable among caecilians (
<figureCitation id="135F38D1FFBDFFFFEEFA3170D5C4F8C2" box="[418,485,1881,1905]" captionStart="Figure 14" captionStartId="17.[112,177,932,956]" captionTargetBox="[114,1458,143,904]" captionTargetId="figure-536@17.[114,1458,143,904]" captionTargetPageId="17" captionText="Figure 14. Left pseudangulars of four different caecilian species. Ymboirana acrux gen. et sp. nov. in lateral (A1) and dorsal (A2) views. Rhinatrema bivitatum in lateral (B1) and dorsal (B2) views. Scolecomorphus ulugurensis in lateral (C1) and dorsal (C2) views.Tophlonectes natans in lateral (D1) and dorsal (D2) views. See Appendix for abbreviations. Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333183" httpUri="https://zenodo.org/record/14333183/files/figure.png" pageId="16" pageNumber="17">Fig. 14</figureCitation>
). In some taxa, the distal tips aredirectedalmostcompletelydorsomedially(e.g.
<taxonomicName id="4C645FD7FFBDFFFFED353151D521F81C" authority=", Uraeotophlus" authorityName="Uraeotophlus" class="Amphibia" family="Scolecomorphidae" genus="Scolecomorphus" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBDFFFFED353151D725F823" box="[621,772,1912,1936]" italics="true" pageId="16" pageNumber="17">Scolecomorphus</emphasis>
,
<emphasis id="B910F846FFBDFFFFEFD931BED521F81C" box="[129,256,1943,1967]" italics="true" pageId="16" pageNumber="17">Uraeotyphlus</emphasis>
</taxonomicName>
, and
<taxonomicName id="4C645FD7FFBDFFFFEE6C31BED592F81C" authorityName="Nussbaum and Wilkinson" authorityYear="1995" box="[308,435,1943,1967]" class="Amphibia" family="Typhlonectidae" genus="Atretochoana" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBDFFFFEE6C31BED592F81C" box="[308,435,1943,1967]" italics="true" pageId="16" pageNumber="17">Atretochoana</emphasis>
</taxonomicName>
), whereas in most species they are directed posterodorsally (e.g. caeciliids, ichthyophiids, and most typhlonectids). In
<taxonomicName id="4C645FD7FFBDFFFFECA930F2D07BF940" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1009,1114,1755,1779]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBDFFFFECA930F2D07BF940" box="[1009,1114,1755,1779]" italics="true" pageId="16" pageNumber="17">Ymboirana</emphasis>
</taxonomicName>
it is oriented posteriorly, a condition found in some, but not all, individuals of
<taxonomicName id="4C645FD7FFBDFFFFEB8F30D2D1B7F8A0" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" box="[1239,1430,1787,1811]" class="Amphibia" family="Typhlonectidae" genus="Tophlonectes" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="species" species="natans">
<emphasis id="B910F846FFBDFFFFEB8F30D2D1B7F8A0" box="[1239,1430,1787,1811]" italics="true" pageId="16" pageNumber="17">Typhlonectes natans</emphasis>
</taxonomicName>
and
<emphasis id="B910F846FFBDFFFFEC613132D768F881" box="[825,841,1819,1842]" italics="true" pageId="16" pageNumber="17">T</emphasis>
.
<emphasis id="B910F846FFBDFFFFEC0D3133D7C8F881" box="[853,1001,1818,1842]" italics="true" pageId="16" pageNumber="17">compressicauda</emphasis>
. The taxonomic variation regarding this feature remains poorly documented and understood among caecilians, but the shape of the retroarticular process of
<taxonomicName id="4C645FD7FFBDFFFFEBA13170D143F8C2" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1273,1378,1881,1905]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="16" pageNumber="17" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBDFFFFEBA13170D143F8C2" box="[1273,1378,1881,1905]" italics="true" pageId="16" pageNumber="17">Ymboirana</emphasis>
</taxonomicName>
is at least compatible with our interpretation of it as a typhlonectid.
</paragraph>
<paragraph id="8BDB2454FFBDFFFEEC0D31BED630FA77" blockId="16.[825,1475,1755,1999]" lastBlockId="17.[113,763,1076,1476]" lastPageId="17" lastPageNumber="18" pageId="16" pageNumber="17">
Caecilian pseudangulars typically have a well -developed and dorsally projecting processus condyloides, posterior to the articular surface (
<figureCitation id="135F38D1FFBCFFFEEE7E321DD598FBFF" box="[294,441,1076,1100]" captionStart="Figure 11" captionStartId="13.[113,178,1836,1860]" captionTargetBox="[278,1294,144,1808]" captionTargetId="figure-8@13.[278,1294,144,1808]" captionTargetPageId="13" captionText="Figure 11. Caecilian skulls in lateral view. Skull of Siphonops paulensis (A). Skull of Rhinatrema bivitatum (B). Skull of Chthonerpeton indistinctum (C). Interpretive line drawing of Ymboirana acrux gen. et sp. nov. skull (D). See Appendix for abbreviations. Scale bar = 1 mm. Interpretive reconstruction made by Lazare Elbaz." figureDoi="http://doi.org/10.5281/zenodo.14333171" httpUri="https://zenodo.org/record/14333171/files/figure.png" pageId="17" pageNumber="18">Fig. 11B–D, B</figureCitation>
<figureCitation id="135F38D1FFBCFFFEEEE1321DD5D0FBFF" box="[441,497,1076,1100]" captionStart="Figure 1" captionStartId="1.[113,178,1960,1984]" captionTargetBox="[116,1456,1173,1930]" captionTargetId="figure-558@1.[114,1458,1171,1932]" captionTargetPageId="1" captionText="Figure 1. Map of the Taubaté Basin in Southeastern Brazil, showing the type locality for Ymboirana acrux gen. et sp.nov.." figureDoi="http://doi.org/10.5281/zenodo.14333143" httpUri="https://zenodo.org/record/14333143/files/figure.png" pageId="17" pageNumber="18">1–D1</figureCitation>
; Supporting Information,
<figureCitation id="135F38D1FFBCFFFEEF29327AD494FBD8" box="[113,181,1107,1131]" captionStart="Figure 4" captionStartId="5.[115,180,1628,1652]" captionTargetBox="[114,1458,144,1600]" captionTargetId="figure-107@5.[114,1458,144,1600]" captionTargetPageId="5" captionText="Figure 4. Skull bones of Ymboirana acrux gen. et sp. nov. Collapsed fragments of the posterolateral region of the os basale below the right parietal in ventral oblique view (A). Left quadrate and pseudangular in lateral view (B). Left occipital region of the os basale in lateral (C), posterior (D), and dorsal (E) views. Fragments of the left squamosal in lateral view (F). Fragment tentatively assigned to the stapes (G). See Appendix for abbreviations.Scale bars = 1 mm; upper scale bar is for A–F, and the lower one is for G." figureDoi="http://doi.org/10.5281/zenodo.14333151" httpUri="https://zenodo.org/record/14333151/files/figure.png" pageId="17" pageNumber="18">Fig. S4</figureCitation>
). However, the processus condyloides of
<taxonomicName id="4C645FD7FFBCFFFEED0C327AD6DAFBD8" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[596,763,1107,1131]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBCFFFEED0C327AD6DAFBD8" box="[596,763,1107,1131]" italics="true" pageId="17" pageNumber="18">Ymboirana acrux</emphasis>
</taxonomicName>
is small and faint. Additionally, as far as is known, in all caecilians (except
<taxonomicName id="4C645FD7FFBCFFFEEF9A32BBD565FB19" authorityName="Nussbaum and Wilkinson" authorityYear="1995" box="[194,324,1170,1194]" class="Amphibia" family="Typhlonectidae" genus="Atretochoana" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEF9A32BBD565FB19" box="[194,324,1170,1194]" italics="true" pageId="17" pageNumber="18">Atretochoana</emphasis>
</taxonomicName>
;
<bibRefCitation id="EFF559A5FFBCFFFEEE0932BBD6B3FB19" author="Wilkinson M &amp; Nussbaum RA" box="[337,658,1170,1194]" pageId="17" pageNumber="18" pagination="39 - 109" refId="ref14053" refString="Wilkinson M, Nussbaum RA. Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae). Biological Journal of the Linnean Societo 1997; 62: 39 - 109. https: // doi. org / 10.1111 / j. 1095 * 8312.1997. tb 01616. x" type="journal article" year="1997">Wilkinson and Nussbaum 1997</bibRefCitation>
) the fossa at the opening of the canalis primordialis is immediately anterior to the articular surface of pseudangular. In
<taxonomicName id="4C645FD7FFBCFFFEED1F32F9D6D4FB5B" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[583,757,1232,1256]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBCFFFEED1F32F9D6D4FB5B" box="[583,757,1232,1256]" italics="true" pageId="17" pageNumber="18">Ymboirana acrux</emphasis>
</taxonomicName>
, the dorsal region of the pseudangular, anterior to the articular surface, is flat and without signs of such a fossa or a distinct canalis primordialis. We assume this fossa bearing the canalis primordialis should presumably be located in the unpreserved anteriormost portion of the pseudangular, as its complete ab - sence is unknown among caecilians and would imply a complete rearrangement in the skull and lower jaw.
</paragraph>
<caption id="DF1B74DCFFBCFFFEEF28358DD7D8FC40" ID-DOI="http://doi.org/10.5281/zenodo.14333183" ID-Zenodo-Dep="14333183" httpUri="https://zenodo.org/record/14333183/files/figure.png" pageId="17" pageNumber="18" startId="17.[112,177,932,956]" targetBox="[114,1458,143,904]" targetPageId="17" targetType="figure">
<paragraph id="8BDB2454FFBCFFFEEF28358DD7D8FC40" blockId="17.[112,1408,932,1012]" pageId="17" pageNumber="18">
<emphasis id="B910F846FFBCFFFEEF28358DD4F5FC0F" bold="true" box="[112,212,932,956]" pageId="17" pageNumber="18">Figure 14.</emphasis>
Left pseudangulars of four different caecilian species.
<taxonomicName id="4C645FD7FFBCFFFEED97358DD74AFC0F" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[719,875,932,956]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFBCFFFEED97358DD74AFC0F" box="[719,875,932,956]" italics="true" pageId="17" pageNumber="18">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFBCFFFEEC37358DD7D9FC08" box="[879,1016,932,956]" pageId="17" pageNumber="18" rank="species">gen. et sp. nov.</taxonomicNameLabel>
in lateral (A1) and dorsal (A2) views.
<taxonomicName id="4C645FD7FFBCFFFEEF2935E9D561FC6B" baseAuthorityName="Guérin-Méneville" baseAuthorityYear="1838" box="[113,320,960,984]" class="Amphibia" family="Rhinatrematidae" genus="Rhinatrema" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="species" species="bivitatum">
<emphasis id="B910F846FFBCFFFEEF2935E9D561FC6B" box="[113,320,960,984]" italics="true" pageId="17" pageNumber="18">Rhinatrema bivittatum</emphasis>
</taxonomicName>
in lateral (B1) and dorsal (B2) views.
<taxonomicName id="4C645FD7FFBCFFFEEDF035E9D781FC6B" authorityName="Barbour &amp; Loveridge" authorityYear="1928" box="[680,928,960,984]" class="Amphibia" family="Scolecomorphidae" genus="Scolecomorphus" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="species" species="ulugurensis">
<emphasis id="B910F846FFBCFFFEEDF035E9D781FC6B" box="[680,928,960,984]" italics="true" pageId="17" pageNumber="18">Scolecomorphus ulugurensis</emphasis>
</taxonomicName>
in lateral (C1) and dorsal (C2) views.
<taxonomicName id="4C645FD7FFBCFFFEEA5435E9D48CFC47" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" class="Amphibia" family="Typhlonectidae" genus="Tophlonectes" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="species" species="natans">
<emphasis id="B910F846FFBCFFFEEA5435E9D48CFC47" italics="true" pageId="17" pageNumber="18">Typhlonectes natans</emphasis>
</taxonomicName>
in lateral (D1) and dorsal (D2) views. See Appendix for abbreviations. Scale bar = 1 mm.
</paragraph>
</caption>
<paragraph id="8BDB2454FFBCFFFEEE3633CAD5DFFA4E" blockId="17.[113,763,1507,1977]" box="[366,510,1507,1533]" pageId="17" pageNumber="18">
<emphasis id="B910F846FFBCFFFEEE3633CAD5DFFA4E" bold="true" box="[366,510,1507,1533]" pageId="17" pageNumber="18">The dentition</emphasis>
</paragraph>
<paragraph id="8BDB2454FFBCFFFEEF293023D03DFBD8" blockId="17.[113,763,1507,1977]" lastBlockId="17.[810,1462,1076,1977]" pageId="17" pageNumber="18">
Caecilian teeth are pedicellate, mono or bicuspid, and arranged in two upper and one or two lower tooth rows (e.g.
<bibRefCitation id="EFF559A5FFBCFFFEEDCC3000D4CCF9D2" author="Wake MH &amp; Wurst GZ" pageId="17" pageNumber="18" pagination="331 - 41" refId="ref13822" refString="Wake MH, Wurst GZ. Tooth crown morphology in caecilians (Amphibia: Gymnophiona). Journal of Morphologo 1979; 159: 331 - 41. https: // doi. org / 10.1002 / jmor. 1051590304" type="journal article" year="1979">
<collectingCountry id="F37364C4FFBCFFFEEDCC3000D6ECF9F2" box="[660,717,1577,1601]" name="Wake Island" pageId="17" pageNumber="18">Wake</collectingCountry>
and Wurst 1979
</bibRefCitation>
). Adult tooth crown morphology is fairly simple among caecilians but there are some important variations that make tooth morphology helpful for interpreting the affinities of
<taxonomicName id="4C645FD7FFBCFFFEEF29308FD53AF90D" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[113,283,1702,1726]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBCFFFEEF29308FD53AF90D" box="[113,283,1702,1726]" italics="true" pageId="17" pageNumber="18">Ymboirana acrux</emphasis>
</taxonomicName>
, including the number of cusps, degree of size heterodonty within and between tooth rows, degree of recur - vature, the extent to which teeth are slender or robust, the shape of the distal tip, and the presence or absence of blade -like lateral flanges, crenulations, or serrations (e.g.
<bibRefCitation id="EFF559A5FFBCFFFEED54310DD6D4F88F" author="Wake MH &amp; Wurst GZ" box="[524,757,1828,1852]" pageId="17" pageNumber="18" pagination="331 - 41" refId="ref13822" refString="Wake MH, Wurst GZ. Tooth crown morphology in caecilians (Amphibia: Gymnophiona). Journal of Morphologo 1979; 159: 331 - 41. https: // doi. org / 10.1002 / jmor. 1051590304" type="journal article" year="1979">
<collectingCountry id="F37364C4FFBCFFFEED54310DD664F88F" box="[524,581,1828,1852]" name="Wake Island" pageId="17" pageNumber="18">Wake</collectingCountry>
and Wurst 1979
</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBCFFFEEF29316AD4D4F8E8" author="Greven H" box="[113,245,1859,1883]" pageId="17" pageNumber="18" pagination="85 - 90" refId="ref11743" refString="Greven H. On the diversity of tooth crowns in Gymnophiona. Memoires de La Societe Zoologique de France 1986; 43: 85 - 90." type="journal article" year="1986">Greven 1986</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBCFFFEEFA6316AD581F8E8" author="Wilkinson M" box="[254,416,1859,1883]" pageId="17" pageNumber="18" pagination="304 - 11" refId="ref13917" refString="Wilkinson M. Adult tooth crown morphology in the Typhlonectidae (Amphibia: Gymnophiona). Journal of Zoological Sostematics and Evolutionaro Research 1991; 29: 304 - 11. https: // doi. org / 10.1111 / j. 1439 * 0469.1991. tb 00675. x" type="journal article" year="1991">Wilkinson 1991</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBCFFFEEEF2316AD65DF8E8" author="Wilkinson M &amp; O'Connor A &amp; Nussbaum RA" box="[426,636,1859,1883]" pageId="17" pageNumber="18" pagination="1 - 12" refId="ref14257" refString="Wilkinson M, O'Connor A, Nussbaum RA. Taxonomic status of the neotropical caecilian genera Brasilotophlus Taylor, 1968, Microcaecilia Taylor, 1968 and Parvicaecilia Taylor, 1968 (Amphibia: Gymnophiona: Siphonopidae). Occasional Papers of the Museum of Zoologo, Universito of Michigan 2013; 744: 1 - 12." type="journal article" year="2013">
Wilkinson
<emphasis id="B910F846FFBCFFFEED40316DD664F8E8" box="[536,581,1859,1883]" italics="true" pageId="17" pageNumber="18">et al.</emphasis>
2013
</bibRefCitation>
). Structures resembling pedicels located near the mandibular symphyses are tentatively interpreted as forming an inner mandibulary tooth row in
<taxonomicName id="4C645FD7FFBCFFFEEFA33188D584F80A" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[251,421,1953,1977]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBCFFFEEFA33188D584F80A" box="[251,421,1953,1977]" italics="true" pageId="17" pageNumber="18">Ymboirana acrux</emphasis>
</taxonomicName>
that allows us to exclude it from the
<taxonomicName id="4C645FD7FFBCFFFEEC0F321DD7C7FBFF" authorityName="Bonaparte" authorityYear="1850" box="[855,998,1076,1100]" class="Amphibia" family="Siphonopidae" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="family">Siphonopidae</taxonomicName>
-crown, which lack inner mandibular teeth (
<bibRefCitation id="EFF559A5FFBCFFFEEC6D327AD02DFBD8" author="Wilkinson M &amp; San Mauro D &amp; Sherratt E" box="[821,1036,1107,1131]" pageId="17" pageNumber="18" pagination="41 - 64" refId="ref14211" refString="Wilkinson M, San Mauro D, Sherratt E et al. A nine * family classification of caecilians (Amphibia: Gymnophiona). Zootaxa 2011; 2874: 41 - 64. https: // doi. org / 10.11646 / zootaxa. 2874.1.3" type="journal article" year="2011">
Wilkinson
<emphasis id="B910F846FFBCFFFEECFD327DD7F2FBD8" box="[933,979,1107,1131]" italics="true" pageId="17" pageNumber="18">et al.</emphasis>
2011
</bibRefCitation>
).
</paragraph>
<paragraph id="8BDB2454FFBCFFFEEC1D325BD11CF9CC" blockId="17.[810,1462,1076,1977]" pageId="17" pageNumber="18">
Bicuspid teeth are considered primitive within caecilians, and are found (with or without monocusped teeth) in all rhinatrematids, ichthyophiids, chikilids, and grandisoniids, dermophiids (except
<taxonomicName id="4C645FD7FFBCFFFEEB5D32F9D051FB5B" authorityName="Peters" authorityYear="1880" box="[1029,1136,1232,1256]" class="Amphibia" family="Dermophiidae" genus="Dermophis" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEB5D32F9D051FB5B" box="[1029,1136,1232,1256]" italics="true" pageId="17" pageNumber="18">Dermophis</emphasis>
</taxonomicName>
), the siphonopids
<taxonomicName id="4C645FD7FFBCFFFEEA6B32F9D192FB5B" authorityName="Taylor" authorityYear="1968" box="[1331,1459,1232,1256]" class="Amphibia" family="Siphonopidae" genus="Microcaecilia" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEA6B32F9D192FB5B" box="[1331,1459,1232,1256]" italics="true" pageId="17" pageNumber="18">Microcaecilia</emphasis>
</taxonomicName>
and
<emphasis id="B910F846FFBCFFFEEC0332D9D7C7FABB" box="[859,998,1264,1288]" italics="true" pageId="17" pageNumber="18">Brasilotyphlus</emphasis>
, and the herpelid
<taxonomicName id="4C645FD7FFBCFFFEEBEC32D9D112FABB" authorityName="Tornier" authorityYear="1896" box="[1204,1331,1264,1288]" class="Amphibia" family="Herpelidae" genus="Boulengerula" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEBEC32D9D112FABB" box="[1204,1331,1264,1288]" italics="true" pageId="17" pageNumber="18">Boulengerula</emphasis>
</taxonomicName>
(
<bibRefCitation id="EFF559A5FFBCFFFEEA1132D9D785FA94" author="Wake MH &amp; Wurst GZ" pageId="17" pageNumber="18" pagination="331 - 41" refId="ref13822" refString="Wake MH, Wurst GZ. Tooth crown morphology in caecilians (Amphibia: Gymnophiona). Journal of Morphologo 1979; 159: 331 - 41. https: // doi. org / 10.1002 / jmor. 1051590304" type="journal article" year="1979">
<collectingCountry id="F37364C4FFBCFFFEEA1132D9D1A3FABB" box="[1353,1410,1264,1288]" name="Wake Island" pageId="17" pageNumber="18">Wake</collectingCountry>
and Wurst 1979
</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBCFFFEECEA3326D07AFA94" author="Nussbaum RA" box="[946,1115,1295,1319]" pageId="17" pageNumber="18" pagination="921 - 8" refId="ref12776" refString="Nussbaum RA. On the status of Copeotophlinus sontremus, Gomnopis oligozona, and Minascaecilia sartoria (Gymnophiona: Caeciliidae): a comedy of errors. Copeia 1988; 1988: 921 - 8. https: // doi. org / 10.2307 / 1445715" type="journal article" year="1988">Nussbaum 1988</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBCFFFEEB303326D12FFA94" author="Wilkinson M" box="[1128,1294,1295,1319]" pageId="17" pageNumber="18" pagination="423 - 70" refId="ref13967" refString="Wilkinson M. Characters, congruence and quality: a study of neuroana * tomical and traditional data in caecilian phylogeny. Biological Reviews 1997; 72: 423 - 70. https: // doi. org / 10.1111 / j. 1469 * 185 x. 1997. tb 00020. x" type="journal article" year="1997">Wilkinson 1997</bibRefCitation>
; M.W. personal observation). Like caeciliids, typhlonectids, siphonoform siphonopids, scolecomorphids,
<taxonomicName id="4C645FD7FFBCFFFEEBCF3367D0C3FAD5" authorityName="Peters" authorityYear="1880" box="[1175,1250,1358,1382]" class="Amphibia" family="Herpelidae" genus="Herpele" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEBCF3367D0C3FAD5" box="[1175,1250,1358,1382]" italics="true" pageId="17" pageNumber="18">Herpele</emphasis>
</taxonomicName>
, and
<taxonomicName id="4C645FD7FFBCFFFEEA1A3367D18CFAD5" authorityName="Peters" authorityYear="1880" box="[1346,1453,1358,1382]" class="Amphibia" family="Dermophiidae" genus="Dermophis" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEA1A3367D18CFAD5" box="[1346,1453,1358,1382]" italics="true" pageId="17" pageNumber="18">Dermophis</emphasis>
</taxonomicName>
,
<taxonomicName id="4C645FD7FFBCFFFEEC723344D7B4FA36" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[810,917,1389,1413]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEC723344D7B4FA36" box="[810,917,1389,1413]" italics="true" pageId="17" pageNumber="18">Ymboirana</emphasis>
</taxonomicName>
has only monocuspid teeth. There appears to be little variation in the size of individual teeth either within or between toothrowsin
<taxonomicName id="4C645FD7FFBCFFFEECE83385D03AFA77" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[944,1051,1452,1476]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEECE83385D03AFA77" box="[944,1051,1452,1476]" italics="true" pageId="17" pageNumber="18">Ymboirana</emphasis>
</taxonomicName>
,whichissimilartoaquatictyphlonectids (
<taxonomicName id="4C645FD7FFBCFFFEEC6D33E2D137FA50" authority=", Tophlonectes, and Potomotophlus" authorityName="Tophlonectes, and Potomotophlus" box="[821,1302,1483,1507]" class="Amphibia" family="Typhlonectidae" genus="Atretochoana" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEC6D33E2D796FA50" box="[821,951,1483,1507]" italics="true" pageId="17" pageNumber="18">Atretochoana</emphasis>
,
<emphasis id="B910F846FFBCFFFEEC9F33E2D065FA50" box="[967,1092,1483,1507]" italics="true" pageId="17" pageNumber="18">Typhlonectes</emphasis>
, and
<emphasis id="B910F846FFBCFFFEEBDC33E2D137FA50" box="[1156,1302,1483,1507]" italics="true" pageId="17" pageNumber="18">Potomotyphlus</emphasis>
</taxonomicName>
) and different from the more semi -aquatic typhlonectids
<taxonomicName id="4C645FD7FFBCFFFEEBAA33C3D1A2F9B1" authorityName="Peters" authorityYear="1879" box="[1266,1411,1514,1538]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEBAA33C3D1A2F9B1" box="[1266,1411,1514,1538]" italics="true" pageId="17" pageNumber="18">Chthonerpeton</emphasis>
</taxonomicName>
and
<taxonomicName id="4C645FD7FFBCFFFEEC723020D788F992" authorityName="Taylor" authorityYear="1968" box="[810,937,1545,1569]" class="Amphibia" family="Typhlonectidae" genus="Nectocaecilia" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEC723020D788F992" box="[810,937,1545,1569]" italics="true" pageId="17" pageNumber="18">Nectocaecilia</emphasis>
</taxonomicName>
, as well as many non -typhlonectids (including scolecomorphids, caeciliids, and herpelids). Judged by their pedicels, teeth of the inner rows are slightly smaller than those of the outer rows, which is typical of aquatic caecilians.
</paragraph>
<paragraph id="8BDB2454FFBCFFFDEC1D30AED685FF54" blockId="17.[810,1462,1076,1977]" lastBlockId="18.[129,777,144,231]" lastPageId="18" lastPageNumber="19" pageId="17" pageNumber="18">
<bibRefCitation id="EFF559A5FFBCFFFEEC1D30AED7DEF92C" author="Wilkinson M" box="[837,1023,1671,1695]" pageId="17" pageNumber="18" pagination="304 - 11" refId="ref13917" refString="Wilkinson M. Adult tooth crown morphology in the Typhlonectidae (Amphibia: Gymnophiona). Journal of Zoological Sostematics and Evolutionaro Research 1991; 29: 304 - 11. https: // doi. org / 10.1111 / j. 1439 * 0469.1991. tb 00675. x" type="journal article" year="1991">Wilkinson (1991)</bibRefCitation>
characterized typhlonectid teeth as mostly conical, recurved, and bearing lateral flanges. Exceptional morphologies include
<emphasis id="B910F846FFBCFFFEEB4130ECD119F96E" box="[1049,1336,1733,1757]" italics="true" pageId="17" pageNumber="18">Typhlonectes compressicauda</emphasis>
, which dif - fers from the other typhlonectids in having dilated, spoon, or chisel -shaped tooth crowns (
<bibRefCitation id="EFF559A5FFBCFFFEEB0A312DD0F9F8AF" author="Greven H" box="[1106,1240,1796,1820]" pageId="17" pageNumber="18" pagination="85 - 90" refId="ref11743" refString="Greven H. On the diversity of tooth crowns in Gymnophiona. Memoires de La Societe Zoologique de France 1986; 43: 85 - 90." type="journal article" year="1986">Greven 1986</bibRefCitation>
), and the monotypic
<emphasis id="B910F846FFBCFFFEEC72310AD79DF888" box="[810,956,1827,1851]" italics="true" pageId="17" pageNumber="18">Potomotyphlus</emphasis>
, which has very slender teeth that are more uni - form and less conical proximally. None of the preserved teeth in
<taxonomicName id="4C645FD7FFBCFFFEEC1C314BD78EF8C9" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[836,943,1890,1914]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="17" pageNumber="18" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBCFFFEEC1C314BD78EF8C9" box="[836,943,1890,1914]" italics="true" pageId="17" pageNumber="18">Ymboirana</emphasis>
</taxonomicName>
have the distinctive morphologies described for
<emphasis id="B910F846FFBCFFFEEAC7314AD7E3F82A" italics="true" pageId="17" pageNumber="18">T. compressicauda</emphasis>
or
<emphasis id="B910F846FFBCFFFEECBC31A8D057F82A" box="[996,1142,1921,1945]" italics="true" pageId="17" pageNumber="18">Potomotyphlus</emphasis>
, and they also seem to lack lat - eral flanges, but these structures are diminutive and consequently especially difficult to observe, given the available resolution in our CT -scans and the fact that no tooth crowns were preserved in the surface of the slabs to allow direct observations.
</paragraph>
<paragraph id="8BDB2454FFBFFFFDEE0C372FD617FE93" blockId="18.[128,779,262,1077]" box="[340,566,262,288]" pageId="18" pageNumber="19">
<emphasis id="B910F846FFBFFFFDEE0C372FD617FE93" bold="true" box="[340,566,262,288]" pageId="18" pageNumber="19">The vertebral column</emphasis>
</paragraph>
<paragraph id="8BDB2454FFBFFFFDEFD93704D6CBFCCA" blockId="18.[128,779,262,1077]" pageId="18" pageNumber="19">
Variation in the vertebral morphology of caecilians exists (e.g.
<bibRefCitation id="EFF559A5FFBFFFFDEFD93765D4D0FED7" author="Peter K" box="[129,241,332,356]" pageId="18" pageNumber="19" pagination="35 - 58" refId="ref12903" refString="Peter K. Die Wirbelsaule der Gymnophionen. Berichte der naturforschung Gesselschass zu Freiburg 1894; 9: 35 - 58." type="journal article" year="1894">Peter 1894</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBFFFFDEFA53765D5FAFED7" author="Estes R &amp; Wake MH" box="[253,475,332,356]" pageId="18" pageNumber="19" pagination="228 - 31" refId="ref11555" refString="Estes R, Wake MH. The first fossil record of caecilian amphibians. Nature 1972; 239: 228 - 31. https: // doi. org / 10.1038 / 239228 b 0" type="journal article" year="1972">
Estes and
<collectingCountry id="F37364C4FFBFFFFDEE3F3765D581FED7" box="[359,416,332,356]" name="Wake Island" pageId="18" pageNumber="19">Wake</collectingCountry>
1972
</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBFFFFDEEB03765D644FED7" author="Taylor EH" box="[488,613,332,356]" pageId="18" pageNumber="19" pagination="219 - 31" refId="ref13618" refString="Taylor EH. Comparative anatomy of caecilian anterior vertebrae. Ne Universito of Kansas Science Bulletin 1977; 51: 219 - 31. https: // doi. org / 10.5962 / bhl. part. 24959" type="journal article" year="1977">Taylor 1977</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBFFFFDED2A3765D506FE30" author="Wilkinson M &amp; Nussbaum RA" pageId="18" pageNumber="19" pagination="39 - 109" refId="ref14053" refString="Wilkinson M, Nussbaum RA. Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae). Biological Journal of the Linnean Societo 1997; 62: 39 - 109. https: // doi. org / 10.1111 / j. 1095 * 8312.1997. tb 01616. x" type="journal article" year="1997">Wilkinson and Nussbaum 1997</bibRefCitation>
), but is very incompletely known and its utility in systematics is underdeveloped. Many postcranial elements, including the atlas and the second vertebrae, are preserved in the
<typeStatus id="54DF9AF6FFBFFFFDEFF137E0D524FE52" box="[169,261,457,481]" pageId="18" pageNumber="19" type="holotype">holotype</typeStatus>
of
<taxonomicName id="4C645FD7FFBFFFFDEE7137E0D5F2FE52" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[297,467,457,481]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBFFFFDEE7137E0D5F2FE52" box="[297,467,457,481]" italics="true" pageId="18" pageNumber="19">Ymboirana acrux</emphasis>
</taxonomicName>
. Because the posterior region of the body was not preserved, and some portions of the ver - tebral column are damaged or compressed, it is not possible to determine the exact number of vertebrae of
<taxonomicName id="4C645FD7FFBFFFFDED1D340ED6CFFD8C" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[581,750,551,575]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBFFFFDED1D340ED6CFFD8C" box="[581,750,551,575]" italics="true" pageId="18" pageNumber="19">Ymboirana acrux</emphasis>
</taxonomicName>
(a total of 67 are recognized). Based on the shape of the preserved posteriormost ones, and comparisons with other caecilians, we conclude that approximately one -half of the specimen’s total body length is preserved. In modern caecilians, the known range in vertebral number is from 68 to 307 (
<bibRefCitation id="EFF559A5FFBFFFFDED5034EDD69FFD6F" author="Lowie A &amp; De Kegel B &amp; Wilkinson M" box="[520,702,708,732]" pageId="18" pageNumber="19" refId="ref12248" refString="Lowie A, De Kegel B, Wilkinson M et al. Regional differences in vertebral shapealongtheaxialskeletonincaecilians (Amphibia: Gymnophiona). Journal of Experimental Biologo 2022 b; 225: jeb 244288." type="journal volume" year="2022">
Lowie
<emphasis id="B910F846FFBFFFFDED1534ECD65AFD6F" box="[589,635,708,732]" italics="true" pageId="18" pageNumber="19">et al.</emphasis>
2022b
</bibRefCitation>
), but it is well -established that vertebral counts vary intraspecifically (e.g.
<bibRefCitation id="EFF559A5FFBFFFFDEFD8352BD4DAFCA9" author="Parker HW" box="[128,251,770,794]" pageId="18" pageNumber="19" pagination="71 - 6" refId="ref12867" refString="Parker HW. Caecilians of the Seychelles Islands with descrip * tion of a new subspecies. Copeia 1958; 1958: 71 - 6. https: // doi. org / 10.2307 / 1440543" type="journal article" year="1958">Parker 1958</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBFFFFDEE5D352BD55EFCA9" author="Taylor EH" box="[261,383,770,794]" pageId="18" pageNumber="19" refId="ref13564" refString="Taylor EH. Ne Caecilians of the World: a Taxonomic Review. Lawrence: University of Kansas Press, 1968." type="book" year="1968">Taylor 1968</bibRefCitation>
). Given the constraints on interpreting this character, we only made limited use of it, allowing us to rule out putative affinities between
<taxonomicName id="4C645FD7FFBFFFFDEE993568D60DFCEA" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[449,556,833,857]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEE993568D60DFCEA" box="[449,556,833,857]" italics="true" pageId="18" pageNumber="19">Ymboirana</emphasis>
</taxonomicName>
and abbreviated taxa (e.g. some species of
<emphasis id="B910F846FFBFFFFDEE0D3549D5F3FCCB" box="[341,466,864,888]" italics="true" pageId="18" pageNumber="19">Hypogeophis</emphasis>
; see:
<bibRefCitation id="EFF559A5FFBFFFFDED533549D6F8FCCA" author="Maddock ST &amp; Wilkinson M &amp; Gower DJ" box="[523,729,864,889]" pageId="18" pageNumber="19" pagination="359 - 75" refId="ref12414" refString="Maddock ST, Wilkinson M, Gower DJ. A new species of small, long * snouted Hopogeophis Peters, 1880 (Amphibia: Gymnophiona: Indotyphlidae) from the highest elevations of the Seychelles island of Mahe. Zootaxa 2018; 4450: 359 - 75. https: // doi. org / 10.11646 / zootaxa. 4450.3.3" type="journal article" year="2018">
Maddock
<emphasis id="B910F846FFBFFFFDED2A3548D680FCCB" box="[626,673,864,888]" italics="true" pageId="18" pageNumber="19">et al.</emphasis>
2018
</bibRefCitation>
).
</paragraph>
<paragraph id="8BDB2454FFBFFFFDEFC435A9D0AAFE71" blockId="18.[128,779,262,1077]" lastBlockId="18.[825,1474,144,1077]" pageId="18" pageNumber="19">
The neural arch of the atlas in
<taxonomicName id="4C645FD7FFBFFFFDEE9B35A9D60FFC2B" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[451,558,896,920]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEE9B35A9D60FFC2B" box="[451,558,896,920]" italics="true" pageId="18" pageNumber="19">Ymboirana</emphasis>
</taxonomicName>
lacks a distinct neural spine. Among extant typhlonectids, well -developed neural spines in the atlas are present in
<taxonomicName id="4C645FD7FFBFFFFDEE903597D678FC65" authorityName="Peters" authorityYear="1879" box="[456,601,958,982]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEE903597D678FC65" box="[456,601,958,982]" italics="true" pageId="18" pageNumber="19">Chthonerpeton</emphasis>
</taxonomicName>
and
<taxonomicName id="4C645FD7FFBFFFFDEDD33597D72BFC65" authorityName="Taylor" authorityYear="1968" box="[651,778,958,982]" class="Amphibia" family="Typhlonectidae" genus="Nectocaecilia" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEDD33597D72BFC65" box="[651,778,958,982]" italics="true" pageId="18" pageNumber="19">Nectocaecilia</emphasis>
</taxonomicName>
(
<figureCitation id="135F38D1FFBFFFFDEFD335F7D4C2FC45" box="[139,227,990,1014]" captionStart="Figure 15" captionStartId="18.[129,194,1899,1923]" captionTargetBox="[129,1473,1111,1872]" captionTargetId="figure-568@18.[129,1473,1111,1872]" captionTargetPageId="18" captionText="Figure 15. Atlases of four different typhlonectid caecilians. Ymboirana acrux gen. et sp. nov. in anterior (A1) and dorsal (A2) views. Chthonerpeton indistinctum in anterior (B1) and dorsal (B2) views. Potomotophlus kaupii in anterior (C1) and dorsal (C2) views. Nectocaecilia petersii in anterior (D1) and dorsal (D2) views. See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333185" httpUri="https://zenodo.org/record/14333185/files/figure.png" pageId="18" pageNumber="19">Fig. 15B</figureCitation>
<figureCitation id="135F38D1FFBFFFFDEFBB35F7D500FC45" box="[227,289,990,1014]" captionStart="Figure 2" captionStartId="3.[114,179,1836,1860]" captionTargetBox="[238,1336,144,1808]" captionTargetId="figure-8@3.[238,1336,144,1808]" captionTargetPageId="3" captionText="Figure 2. Fossil slabs containing the holotype (DGM 1462-R) of Ymboirana acrux gen. et sp. nov. (A1, B1). CT-scans of the part (A2) and counterpart (B2) of the holotype.Scale bar = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.14333145" httpUri="https://zenodo.org/record/14333145/files/figure.png" pageId="18" pageNumber="19">2, D2</figureCitation>
), whereas in the remaining typhlonectids (e.g.
<emphasis id="B910F846FFBFFFFDEFD835D4D4DCFBA6" box="[128,253,1021,1045]" italics="true" pageId="18" pageNumber="19">Typhlonectes</emphasis>
and
<taxonomicName id="4C645FD7FFBFFFFDEE7535D4D58EFBA6" box="[301,431,1021,1045]" class="Amphibia" family="Typhlonectidae" genus="Atretochoana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEE7535D4D58EFBA6" box="[301,431,1021,1045]" italics="true" pageId="18" pageNumber="19">Atretochoana</emphasis>
</taxonomicName>
) they are limited to faint ridges or even completely absent, such as in
<emphasis id="B910F846FFBFFFFDEEB63235D6A1FB87" box="[494,640,1052,1076]" italics="true" pageId="18" pageNumber="19">Potomotyphlus</emphasis>
(
<figureCitation id="135F38D1FFBFFFFDEDCA3235D6CAFB87" box="[658,747,1052,1076]" captionStart="Figure 15" captionStartId="18.[129,194,1899,1923]" captionTargetBox="[129,1473,1111,1872]" captionTargetId="figure-568@18.[129,1473,1111,1872]" captionTargetPageId="18" captionText="Figure 15. Atlases of four different typhlonectid caecilians. Ymboirana acrux gen. et sp. nov. in anterior (A1) and dorsal (A2) views. Chthonerpeton indistinctum in anterior (B1) and dorsal (B2) views. Potomotophlus kaupii in anterior (C1) and dorsal (C2) views. Nectocaecilia petersii in anterior (D1) and dorsal (D2) views. See Appendix for abbreviations.Scale bar = 1 mm." figureDoi="http://doi.org/10.5281/zenodo.14333185" httpUri="https://zenodo.org/record/14333185/files/figure.png" pageId="18" pageNumber="19">Fig. 15C</figureCitation>
<figureCitation id="135F38D1FFBFFFFDEDB33235D6D8FB87" box="[747,761,1052,1076]" captionStart="Figure 2" captionStartId="3.[114,179,1836,1860]" captionTargetBox="[238,1336,144,1808]" captionTargetId="figure-8@3.[238,1336,144,1808]" captionTargetPageId="3" captionText="Figure 2. Fossil slabs containing the holotype (DGM 1462-R) of Ymboirana acrux gen. et sp. nov. (A1, B1). CT-scans of the part (A2) and counterpart (B2) of the holotype.Scale bar = 1 cm." figureDoi="http://doi.org/10.5281/zenodo.14333145" httpUri="https://zenodo.org/record/14333145/files/figure.png" pageId="18" pageNumber="19">2</figureCitation>
).
<taxonomicName id="4C645FD7FFBFFFFDEC6136B9D785FF1B" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[825,932,144,168]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEC6136B9D785FF1B" box="[825,932,144,168]" italics="true" pageId="18" pageNumber="19">Ymboirana</emphasis>
</taxonomicName>
trunk vertebrae have the typical pattern of cae - cilian vertebrae, including the presence of medially constricted amphicoelous centra bearing well -developed hypapophyseal keels and large, anteriorly projecting basapophyseal processes (e.g.
<bibRefCitation id="EFF559A5FFBFFFFDEC343724D7C1FE96" author="Wake MH" box="[876,992,269,293]" pageId="18" pageNumber="19" pagination="117 - 30" refId="ref13684" refString="Wake MH. Morphometrics of the skeleton of Dermophis mexicanus (Amphibia: Gymnophiona) Part I The vertebrae, with comparisons to other species. Journal of Morphologo 1980; 165: 117 - 30. https: // doi. org / 10.1002 / jmor. 1051650202" type="journal article" year="1980">
<collectingCountry id="F37364C4FFBFFFFDEC343724D784FE96" box="[876,933,269,293]" name="Wake Island" pageId="18" pageNumber="19">Wake</collectingCountry>
1980
</bibRefCitation>
). Morphological variations within this general pattern are virtually unknown for most caecilians, hampering our interpretations; however,
<taxonomicName id="4C645FD7FFBFFFFDEB183765D0C0FED7" authorityName="Taylor" authorityYear="1968" box="[1088,1249,332,356]" class="Amphibia" family="Typhlonectidae" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="family">Typhlonectidae</taxonomicName>
are the only family in which differences in the postcranial osteology have been docu - mented in any detail (e.g.
<bibRefCitation id="EFF559A5FFBFFFFDEB1137A3D09FFE11" author="Wake MH" box="[1097,1214,394,418]" pageId="18" pageNumber="19" pagination="117 - 30" refId="ref13684" refString="Wake MH. Morphometrics of the skeleton of Dermophis mexicanus (Amphibia: Gymnophiona) Part I The vertebrae, with comparisons to other species. Journal of Morphologo 1980; 165: 117 - 30. https: // doi. org / 10.1002 / jmor. 1051650202" type="journal article" year="1980">
<collectingCountry id="F37364C4FFBFFFFDEB1137A3D0A3FE11" box="[1097,1154,394,418]" name="Wake Island" pageId="18" pageNumber="19">Wake</collectingCountry>
1980
</bibRefCitation>
, Azpelicuelta
<emphasis id="B910F846FFBFFFFDEA0937A2D1A3FE11" box="[1361,1410,394,418]" italics="true" pageId="18" pageNumber="19">et al.</emphasis>
1987,
<bibRefCitation id="EFF559A5FFBFFFFDEC613783D05AFE71" author="Wilkinson M &amp; Nussbaum RA" box="[825,1147,426,450]" pageId="18" pageNumber="19" pagination="191 - 223" refId="ref14113" refString="Wilkinson M, Nussbaum RA. Evolutionary relationships of the lung * less caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae). Zoological Journal of the Linnean Societo 1999; 126: 191 - 223. https: // doi. org / 10.1111 / j. 1096 * 3642.1999. tb 00153. x" type="journal article" year="1999">Wilkinson and Nussbaum 1999</bibRefCitation>
).
</paragraph>
<paragraph id="8BDB2454FFBFFFFDEC0D37E0D0CEFC8A" blockId="18.[825,1474,144,1077]" pageId="18" pageNumber="19">
The obligate aquatic typhlonectids (
<taxonomicName id="4C645FD7FFBFFFFDEA6237E0D0A2FDB3" authority=", Potomotophlus, and Tophlonectes" authorityName="Potomotophlus, and Tophlonectes" class="Amphibia" family="Typhlonectidae" genus="Atretochoana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEA6237E0D19DFE52" box="[1338,1468,457,481]" italics="true" pageId="18" pageNumber="19">Atretochoana</emphasis>
,
<emphasis id="B910F846FFBFFFFDEC6137C1D7EAFDB3" box="[825,971,488,512]" italics="true" pageId="18" pageNumber="19">Potomotyphlus</emphasis>
, and
<emphasis id="B910F846FFBFFFFDEB5E37C1D0A2FDB3" box="[1030,1155,488,512]" italics="true" pageId="18" pageNumber="19">Typhlonectes</emphasis>
</taxonomicName>
) have distinctive elongate and narrow trunk vertebrae compared to other caecilians (
<bibRefCitation id="EFF559A5FFBFFFFDEA003421D035FD8C" author="Wilkinson M &amp; Nussbaum RA" pageId="18" pageNumber="19" pagination="39 - 109" refId="ref14053" refString="Wilkinson M, Nussbaum RA. Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae). Biological Journal of the Linnean Societo 1997; 62: 39 - 109. https: // doi. org / 10.1111 / j. 1095 * 8312.1997. tb 01616. x" type="journal article" year="1997">Wilkinson and Nussbaum 1997</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBFFFFDEB7B340ED076FD8C" author="Wilkinson M &amp; Nussbaum RA" box="[1059,1111,551,575]" pageId="18" pageNumber="19" pagination="191 - 223" refId="ref14113" refString="Wilkinson M, Nussbaum RA. Evolutionary relationships of the lung * less caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae). Zoological Journal of the Linnean Societo 1999; 126: 191 - 223. https: // doi. org / 10.1111 / j. 1096 * 3642.1999. tb 00153. x" type="journal article" year="1999">1999</bibRefCitation>
). Additionally, their neural spines are limited to faint ridges or are absent from most vertebrae (
<bibRefCitation id="EFF559A5FFBFFFFDEC1C344FD0AEFDCD" author="Wilkinson M &amp; Nussbaum RA" box="[836,1167,614,638]" pageId="18" pageNumber="19" pagination="191 - 223" refId="ref14113" refString="Wilkinson M, Nussbaum RA. Evolutionary relationships of the lung * less caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae). Zoological Journal of the Linnean Societo 1999; 126: 191 - 223. https: // doi. org / 10.1111 / j. 1096 * 3642.1999. tb 00153. x" type="journal article" year="1999">Wilkinson and Nussbaum 1999</bibRefCitation>
). The latter condition is also observed in the similarly elongate trunk vertebrae of
<taxonomicName id="4C645FD7FFBFFFFDEA0934ACD19DFD2E" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1361,1468,645,669]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEA0934ACD19DFD2E" box="[1361,1468,645,669]" italics="true" pageId="18" pageNumber="19">Ymboirana</emphasis>
</taxonomicName>
, in which the ridge is hardly distinguished dorsally. Ventral ridges on the basapophyseal processes constitute another distinctive feature of typhlonectids other than
<taxonomicName id="4C645FD7FFBFFFFDEBEA34CAD039FCA9" authority="(Wilkinson and Nussbaum 1999)" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEBEA34CAD162FD48" box="[1202,1347,739,763]" italics="true" pageId="18" pageNumber="19">Chthonerpeton</emphasis>
(
<bibRefCitation id="EFF559A5FFBFFFFDEA0034CAD02DFCA9" author="Wilkinson M &amp; Nussbaum RA" pageId="18" pageNumber="19" pagination="191 - 223" refId="ref14113" refString="Wilkinson M, Nussbaum RA. Evolutionary relationships of the lung * less caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae). Zoological Journal of the Linnean Societo 1999; 126: 191 - 223. https: // doi. org / 10.1111 / j. 1096 * 3642.1999. tb 00153. x" type="journal article" year="1999">Wilkinson and Nussbaum 1999</bibRefCitation>
)
</taxonomicName>
. These ventral ridges are particularly well - developed in trunk vertebrae of
<taxonomicName id="4C645FD7FFBFFFFDEB26350BD0C8FC89" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1150,1257,802,826]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEB26350BD0C8FC89" box="[1150,1257,802,826]" italics="true" pageId="18" pageNumber="19">Ymboirana</emphasis>
</taxonomicName>
.
</paragraph>
<paragraph id="8BDB2454FFBFFFFCEC0D3568D497FF54" blockId="18.[825,1474,144,1077]" lastBlockId="19.[113,762,144,231]" lastPageId="19" lastPageNumber="20" pageId="18" pageNumber="19">
The
<typeStatus id="54DF9AF6FFBFFFFDECDC3568D7C1FCEA" box="[900,992,833,857]" pageId="18" pageNumber="19" type="holotype">holotype</typeStatus>
of
<taxonomicName id="4C645FD7FFBFFFFDEB5C3568D08EFCEA" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1028,1199,833,857]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBFFFFDEB5C3568D08EFCEA" box="[1028,1199,833,857]" italics="true" pageId="18" pageNumber="19">Ymboirana acrux</emphasis>
</taxonomicName>
also preserves several ribs along its vertebral column, but most are badly damaged. Two ribs, preserved near a trunk vertebra located at the middle por - tion of the specimen, remain almost fully preserved. These ribs are relatively straight, and also dorsoventrally expanded at their anteriormost portion, narrowing distally as in the more aquatic typhlonectids (i.e. not
<taxonomicName id="4C645FD7FFBFFFFDEBD935D4D133FBA6" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" box="[1153,1298,1021,1045]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEBD935D4D133FBA6" box="[1153,1298,1021,1045]" italics="true" pageId="18" pageNumber="19">Chthonerpeton</emphasis>
</taxonomicName>
or
<taxonomicName id="4C645FD7FFBFFFFDEA6435D4D19AFBA6" authorityName="Taylor" authorityYear="1968" box="[1340,1467,1021,1045]" class="Amphibia" family="Typhlonectidae" genus="Nectocaecilia" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBFFFFDEA6435D4D19AFBA6" box="[1340,1467,1021,1045]" italics="true" pageId="18" pageNumber="19">Nectocaecilia</emphasis>
</taxonomicName>
; see:
<bibRefCitation id="EFF559A5FFBFFFFDEC343234D0E0FB86" author="Wilkinson M &amp; Nussbaum RA" box="[876,1217,1053,1077]" pageId="18" pageNumber="19" pagination="191 - 223" refId="ref14113" refString="Wilkinson M, Nussbaum RA. Evolutionary relationships of the lung * less caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae). Zoological Journal of the Linnean Societo 1999; 126: 191 - 223. https: // doi. org / 10.1111 / j. 1096 * 3642.1999. tb 00153. x" type="journal article" year="1999">Wilkinson and Nussbaum 1999</bibRefCitation>
). The capitula of these ribs are elongate anteriorly, a feature previously reported as an apomorphy of
<taxonomicName id="4C645FD7FFBEFFFCEE573686D490FF54" authority="(Wilkinson and Nussbaum 1999)" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" class="Amphibia" family="Typhlonectidae" genus="Tophlonectes" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="species" species="natans">
<emphasis id="B910F846FFBEFFFCEE573686D5F7FF74" box="[271,470,175,199]" italics="true" pageId="19" pageNumber="20">Typhlonectes natans</emphasis>
(
<bibRefCitation id="EFF559A5FFBEFFFCEEB23686D484FF54" author="Wilkinson M &amp; Nussbaum RA" pageId="19" pageNumber="20" pagination="191 - 223" refId="ref14113" refString="Wilkinson M, Nussbaum RA. Evolutionary relationships of the lung * less caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae). Zoological Journal of the Linnean Societo 1999; 126: 191 - 223. https: // doi. org / 10.1111 / j. 1096 * 3642.1999. tb 00153. x" type="journal article" year="1999">Wilkinson and Nussbaum 1999</bibRefCitation>
)
</taxonomicName>
.
</paragraph>
<caption id="DF1B74DCFFBFFFFDEFD93142D03CF808" ID-DOI="http://doi.org/10.5281/zenodo.14333185" ID-Zenodo-Dep="14333185" httpUri="https://zenodo.org/record/14333185/files/figure.png" pageId="18" pageNumber="19" startId="18.[129,194,1899,1923]" targetBox="[129,1473,1111,1872]" targetPageId="18" targetType="figure">
<paragraph id="8BDB2454FFBFFFFDEFD93142D03CF808" blockId="18.[129,1454,1899,1980]" pageId="18" pageNumber="19">
<emphasis id="B910F846FFBFFFFDEFD93142D4C4F830" bold="true" box="[129,229,1899,1923]" pageId="18" pageNumber="19">Figure 15.</emphasis>
Atlases of four different typhlonectid caecilians.
<taxonomicName id="4C645FD7FFBFFFFDEDF73145D76AF830" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[687,843,1900,1924]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="species" species="acrux" status="gen. et sp. nov.">
<emphasis id="B910F846FFBFFFFDEDF73145D76AF830" box="[687,843,1900,1924]" italics="true" pageId="18" pageNumber="19">Ymboirana acrux</emphasis>
</taxonomicName>
<taxonomicNameLabel id="A223453DFFBFFFFDEC173145D7F9F830" box="[847,984,1900,1924]" pageId="18" pageNumber="19" rank="species">gen. et sp. nov.</taxonomicNameLabel>
in anterior (A1) and dorsal (A2) views.
<taxonomicName id="4C645FD7FFBFFFFDEFD931A1D55DF813" baseAuthorityName="Reinhardt &amp; Lutken" baseAuthorityYear="1862" box="[129,380,1928,1952]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="species" species="indistinctum">
<emphasis id="B910F846FFBFFFFDEFD931A1D55DF813" box="[129,380,1928,1952]" italics="true" pageId="18" pageNumber="19">Chthonerpeton indistinctum</emphasis>
</taxonomicName>
in anterior (B1) and dorsal (B2) views.
<taxonomicName id="4C645FD7FFBFFFFDEDAE31A1D79AF813" baseAuthorityName="Berthold" baseAuthorityYear="1859" box="[758,955,1928,1952]" class="Amphibia" family="Typhlonectidae" genus="Potomotophlus" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="species" species="kaupii">
<emphasis id="B910F846FFBFFFFDEDAE31A1D79AF813" box="[758,955,1928,1952]" italics="true" pageId="18" pageNumber="19">Potomotyphlus kaupii</emphasis>
</taxonomicName>
in anterior (C1) and dorsal (C2) views.
<taxonomicName id="4C645FD7FFBFFFFDEA6131A1D4E0F808" baseAuthorityName="Boulenger" baseAuthorityYear="1882" class="Amphibia" family="Typhlonectidae" genus="Nectocaecilia" kingdom="Animalia" order="Gymnophiona" pageId="18" pageNumber="19" phylum="Chordata" rank="species" species="petersii">
<emphasis id="B910F846FFBFFFFDEA6131A1D4E0F808" italics="true" pageId="18" pageNumber="19">Nectocaecilia petersii</emphasis>
</taxonomicName>
in anterior (D1) and dorsal (D2) views. See Appendix for abbreviations. Scale bar = 1 mm.
</paragraph>
</caption>
<paragraph id="8BDB2454FFBEFFFCEF88372FD6BAFE92" blockId="19.[113,763,262,1327]" box="[208,667,262,289]" pageId="19" pageNumber="20">
<emphasis id="B910F846FFBEFFFCEF88372FD5CBFE93" bold="true" box="[208,490,262,288]" pageId="19" pageNumber="20">The taxonomic affinities of</emphasis>
<taxonomicName id="4C645FD7FFBEFFFCEEB6372FD6BAFE92" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[494,667,262,289]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBEFFFCEEB6372FD6BAFE92" bold="true" box="[494,667,262,289]" italics="true" pageId="19" pageNumber="20">Ymboirana acrux</emphasis>
</taxonomicName>
</paragraph>
<paragraph id="8BDB2454FFBEFFFCEF293704D69AFCA9" blockId="19.[113,763,262,1327]" pageId="19" pageNumber="20">
According to the most recent classification proposal of
<taxonomicName id="4C645FD7FFBEFFFCEF293765D528FED7" authorityName="Rafinesque" authorityYear="1814" box="[113,265,332,356]" class="Amphibia" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="order">Gymnophiona</taxonomicName>
, representatives of the family
<taxonomicName id="4C645FD7FFBEFFFCED013765D6DBFED7" authorityName="Taylor" authorityYear="1968" box="[601,762,332,356]" class="Amphibia" family="Typhlonectidae" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="family">Typhlonectidae</taxonomicName>
can be differentiated from all other caecilians by having fused, sheet - or sac -like embryonic gills (
<bibRefCitation id="EFF559A5FFBEFFFCEE8137A2D697FE10" author="Wilkinson M &amp; San Mauro D &amp; Sherratt E" box="[473,694,395,419]" pageId="19" pageNumber="20" pagination="41 - 64" refId="ref14211" refString="Wilkinson M, San Mauro D, Sherratt E et al. A nine * family classification of caecilians (Amphibia: Gymnophiona). Zootaxa 2011; 2874: 41 - 64. https: // doi. org / 10.11646 / zootaxa. 2874.1.3" type="journal article" year="2011">
Wilkinson
<emphasis id="B910F846FFBEFFFCED1337A2D65DFE10" box="[587,636,395,419]" italics="true" pageId="19" pageNumber="20">et al.</emphasis>
2011
</bibRefCitation>
). This minimal diagnosis, although useful for the taxonomy of living groups, cannot be applied to the case of
<taxonomicName id="4C645FD7FFBEFFFCED7837E0D6AAFE52" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[544,651,457,481]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCED7837E0D6AAFE52" box="[544,651,457,481]" italics="true" pageId="19" pageNumber="20">Ymboirana</emphasis>
</taxonomicName>
given that early life -history stages are unknown.
<bibRefCitation id="EFF559A5FFBEFFFCEEA937C0D49DFD93" author="Wilkinson M &amp; Nussbaum RA" pageId="19" pageNumber="20" pagination="191 - 223" refId="ref14113" refString="Wilkinson M, Nussbaum RA. Evolutionary relationships of the lung * less caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae). Zoological Journal of the Linnean Societo 1999; 126: 191 - 223. https: // doi. org / 10.1111 / j. 1096 * 3642.1999. tb 00153. x" type="journal article" year="1999">Wilkinson and Nussbaum (1999)</bibRefCitation>
have provided an extended diagnosis of
<taxonomicName id="4C645FD7FFBEFFFCED013421D6DBFD93" authorityName="Taylor" authorityYear="1968" box="[601,762,520,544]" class="Amphibia" family="Typhlonectidae" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="family">Typhlonectidae</taxonomicName>
and listed 28 features that are considered derived among teresomatan caecilians. However, the conditions of most of these are also unknown in
<taxonomicName id="4C645FD7FFBEFFFCEE1B344FD58FFDCD" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[323,430,614,638]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCEE1B344FD58FFDCD" box="[323,430,614,638]" italics="true" pageId="19" pageNumber="20">Ymboirana</emphasis>
</taxonomicName>
(either because they are features of soft anatomy or of unpreserved regions of the skeleton). Of these characters, only the presence of monocusped teeth can be verified reliably in
<taxonomicName id="4C645FD7FFBEFFFCEE7234EDD5B4FD6F" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[298,405,708,732]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCEE7234EDD5B4FD6F" box="[298,405,708,732]" italics="true" pageId="19" pageNumber="20">Ymboirana</emphasis>
</taxonomicName>
, and this feature is known in several non -typhlonectid caecilians too. Thus, unambiguous synapo - morphies of
<taxonomicName id="4C645FD7FFBEFFFCEFAA352BD5B2FCA9" authorityName="Taylor" authorityYear="1968" box="[242,403,770,794]" class="Amphibia" family="Typhlonectidae" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="family">Typhlonectidae</taxonomicName>
are not known in
<taxonomicName id="4C645FD7FFBEFFFCED12352BD694FCA9" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[586,693,770,794]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCED12352BD694FCA9" box="[586,693,770,794]" italics="true" pageId="19" pageNumber="20">Ymboirana</emphasis>
</taxonomicName>
.
</paragraph>
<paragraph id="8BDB2454FFBEFFFCEFD5350BD537FA9C" blockId="19.[113,763,262,1327]" pageId="19" pageNumber="20">
But the typhlonectid affinities of
<taxonomicName id="4C645FD7FFBEFFFCEE86350BD668FC89" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[478,585,802,826]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCEE86350BD668FC89" box="[478,585,802,826]" italics="true" pageId="19" pageNumber="20">Ymboirana</emphasis>
</taxonomicName>
are evidenced by features it shares with some, but not all, living representatives of
<taxonomicName id="4C645FD7FFBEFFFCEFD53549D510FCCB" authorityName="Taylor" authorityYear="1968" box="[141,305,864,888]" class="Amphibia" family="Typhlonectidae" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="family">Typhlonectidae</taxonomicName>
. For example, the presence of ventral ridges in the basapophyseal processes is reported in all typhlonectids except
<taxonomicName id="4C645FD7FFBEFFFCEFE235B6D56AFC04" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" box="[186,331,927,951]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCEFE235B6D56AFC04" box="[186,331,927,951]" italics="true" pageId="19" pageNumber="20">Chthonerpeton</emphasis>
</taxonomicName>
, and the presence of elongate and narrow trunk vertebrae and strongly distally tapering ribs are known exclusively in the subgroup of fully aquatic typhlonectids (i.e.
<emphasis id="B910F846FFBEFFFCEF2935D4D4CFFBA6" box="[113,238,1021,1045]" italics="true" pageId="19" pageNumber="20">Typhlonectes</emphasis>
,
<emphasis id="B910F846FFBEFFFCEFA535D4D5AEFBA6" box="[253,399,1021,1045]" italics="true" pageId="19" pageNumber="20">Potomotyphlus</emphasis>
, and
<taxonomicName id="4C645FD7FFBEFFFCEE9535D4D66EFBA6" box="[461,591,1021,1045]" class="Amphibia" family="Typhlonectidae" genus="Atretochoana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCEE9535D4D66EFBA6" box="[461,591,1021,1045]" italics="true" pageId="19" pageNumber="20">Atretochoana</emphasis>
</taxonomicName>
; see:
<bibRefCitation id="EFF559A5FFBEFFFCEDC835D4D56DFB86" author="Wilkinson M &amp; Nussbaum RA" pageId="19" pageNumber="20" pagination="191 - 223" refId="ref14113" refString="Wilkinson M, Nussbaum RA. Evolutionary relationships of the lung * less caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae). Zoological Journal of the Linnean Societo 1999; 126: 191 - 223. https: // doi. org / 10.1111 / j. 1096 * 3642.1999. tb 00153. x" type="journal article" year="1999">Wilkinson and Nussbaum 1999</bibRefCitation>
). Further, the presence of a strong ven - tral sloping on the parietals, as well as the straightness of the ribs and the lack of posterior flexure, are at least reminiscent of
<taxonomicName id="4C645FD7FFBEFFFCEFD73253D501FB21" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" box="[143,288,1146,1170]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCEFD73253D501FB21" box="[143,288,1146,1170]" italics="true" pageId="19" pageNumber="20">Chthonerpeton</emphasis>
</taxonomicName>
and
<taxonomicName id="4C645FD7FFBEFFFCEE003253D490FB01" authority="(Wilkinson and Nussbaum 1999)" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" class="Amphibia" family="Typhlonectidae" genus="Nectocaecilia" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCEE003253D5F6FB21" box="[344,471,1146,1170]" italics="true" pageId="19" pageNumber="20">Nectocaecilia</emphasis>
(
<bibRefCitation id="EFF559A5FFBEFFFCEEB33253D484FB01" author="Wilkinson M &amp; Nussbaum RA" pageId="19" pageNumber="20" pagination="191 - 223" refId="ref14113" refString="Wilkinson M, Nussbaum RA. Evolutionary relationships of the lung * less caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae). Zoological Journal of the Linnean Societo 1999; 126: 191 - 223. https: // doi. org / 10.1111 / j. 1096 * 3642.1999. tb 00153. x" type="journal article" year="1999">Wilkinson and Nussbaum 1999</bibRefCitation>
)
</taxonomicName>
. Taken together these features suggest that
<taxonomicName id="4C645FD7FFBEFFFCED2032B3D6C2FB01" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[632,739,1178,1202]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCED2032B3D6C2FB01" box="[632,739,1178,1202]" italics="true" pageId="19" pageNumber="20">Ymboirana</emphasis>
</taxonomicName>
is more closely related to the fully aquatic typhlonectids than it is to
<taxonomicName id="4C645FD7FFBEFFFCEFD332F1D53DFB43" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" box="[139,284,1240,1264]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCEFD332F1D53DFB43" box="[139,284,1240,1264]" italics="true" pageId="19" pageNumber="20">Chthonerpeton</emphasis>
</taxonomicName>
or
<taxonomicName id="4C645FD7FFBEFFFCEE6532F1D59DFB43" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" box="[317,444,1240,1264]" class="Amphibia" family="Typhlonectidae" genus="Nectocaecilia" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCEE6532F1D59DFB43" box="[317,444,1240,1264]" italics="true" pageId="19" pageNumber="20">Nectocaecilia</emphasis>
</taxonomicName>
, and is possibly its sister -group, a hypothesis requiring further evaluation through formal phylo - genetic analysis.
</paragraph>
<paragraph id="8BDB2454FFBEFFFCEE2D3366D5D7FADA" blockId="19.[113,763,1359,1985]" box="[373,502,1359,1385]" pageId="19" pageNumber="20">
<emphasis id="B910F846FFBEFFFCEE2D3366D5D7FADA" bold="true" box="[373,502,1359,1385]" pageId="19" pageNumber="20">Taphonomy</emphasis>
</paragraph>
<paragraph id="8BDB2454FFBEFFFCEF29335CD514F8B6" blockId="19.[113,763,1359,1985]" pageId="19" pageNumber="20">
During the collection of the
<taxonomicName id="4C645FD7FFBEFFFCEEF4335CD67BFA3E" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[428,602,1397,1421]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBEFFFCEEF4335CD67BFA3E" box="[428,602,1397,1421]" italics="true" pageId="19" pageNumber="20">Ymboirana acrux</emphasis>
</taxonomicName>
<typeStatus id="54DF9AF6FFBEFFFCED3C335CD6E1FA3E" box="[612,704,1397,1421]" pageId="19" pageNumber="20" type="holotype">holotype</typeStatus>
skel - eton, taphonomic procedures, such as the definition of the azi - muthal orientation or the top and the bottom of the fossiliferous assemblage, were not followed (e.g.
<bibRefCitation id="EFF559A5FFBEFFFCEEAC33FAD6C8FA58" author="Holz M &amp; Simoes MG" box="[500,745,1491,1515]" pageId="19" pageNumber="20" pagination="249 - 278" refId="ref11849" refString="Holz M, Simoes MG. Taphonomy - overview of main concepts and ap * plications to sequence stratigraphic analysis. In: Koutsoukos EAM (ed.), Applied Stratigrapho. Dordrecht: Springer, 2005, 249 - 278." type="book chapter" year="2005">Holz and Simões 2005</bibRefCitation>
). Because the fossil was originally considered mining tailings, it was stored near other similar materials in a spoil pile exposed to weathering. Furthermore, there are still no studies focused on the taphonomy of caecilian remains. Therefore, taphonomic in - terpretations are naturally restricted. It is also worth mentioning that because lacustrine deposits routinely preserve remains of allochthonous terrestrial animals, our conclusions remain only tentative and based on indirect evidence. Thus, they should be taken with caution.
</paragraph>
<paragraph id="8BDB2454FFBEFFFCEFD53125D7F2FE10" blockId="19.[113,763,1359,1985]" lastBlockId="19.[810,1460,144,1452]" pageId="19" pageNumber="20">
Tremembé Formation is interpreted as having been depos - ited in a playa -lake system developed during the Oligocene (
<bibRefCitation id="EFF559A5FFBEFFFCEF243162D50BF8D0" author="Riccomini C" box="[124,298,1867,1891]" pageId="19" pageNumber="20" refId="ref13048" refString="Riccomini C. O riss continental do sudeste do Brasil. Unpublished D. Phil. Thesis, Universidade de Sao Paulo, 1989." type="book" year="1989">Riccomini 1989</bibRefCitation>
). Lacustrine environments are character - ized by a poorly oxygenated bottom and low energy available for the transport of sediments (e.g.
<bibRefCitation id="EFF559A5FFBEFFFCEEB431A3D64EF811" author="Wetzel RG" box="[492,623,1930,1954]" pageId="19" pageNumber="20" refId="ref13862" refString="Wetzel RG. Limnologo: Lake and River Ecosostems. San Diego: Academic Press, 2001." type="book" year="2001">Wetzel 2001</bibRefCitation>
) and, conse - quently, biological remains. These two factors contribute to the fossilization process in lacustrine systems and both were present in the Tremembé palaeolake (
<bibRefCitation id="EFF559A5FFBEFFFCEB293686D13AFF74" author="Riccomini C" box="[1137,1307,175,199]" pageId="19" pageNumber="20" refId="ref13048" refString="Riccomini C. O riss continental do sudeste do Brasil. Unpublished D. Phil. Thesis, Universidade de Sao Paulo, 1989." type="book" year="1989">Riccomini 1989</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBEFFFCEA733699D77FFF55" author="Bergue CT &amp; Maranhao MDSA &amp; Fauth G" pageId="19" pageNumber="20" pagination="1531 - 44" refId="ref11271" refString="Bergue CT, Maranhao MDSA, Fauth G. Paleolimnological infer * ences based on Oligocene ostracods (Crustacea: Ostracoda) from Tremembe Formation, southeast Brazil. Anais da Academia Brasileira de Ciencias 2015; 87: 1531 - 44." type="journal article" year="2015">
Bergue
<emphasis id="B910F846FFBEFFFCEA273699D195FF74" box="[1407,1460,175,199]" italics="true" pageId="19" pageNumber="20">et al.</emphasis>
2015
</bibRefCitation>
). The other lissamphibian found in Tremembé Formation, a neobatrachian anuran, was described based on damaged and disarticulated remains (Barcelos and Santos 2023). To explain the damaged condition of the specimen, it was proposed that the remains pass through a ‘bloat and float’ stage, which is common for vertebrates fossilized in aquatic environments (e.g.
<bibRefCitation id="EFF559A5FFBEFFFCEA173742D7E3FE10" author="Syme CE &amp; Salisbury SW" pageId="19" pageNumber="20" pagination="108 - 23" refId="ref13477" refString="Syme CE, Salisbury SW. Patterns of aquatic decay and disarticulation in juvenile Indo * Pacific crocodiles (Crocodolus porosus), and implications for the taphonomic interpretation of fossil crocodyliform material. Palaeogeographo, Palaeoclimatologo, Palaeoecologo 2014; 412: 108 - 23. https: // doi. org / 10.1016 / j. palaeo. 2014.07.031" type="journal article" year="2014">Syme and Salisbury 2014</bibRefCitation>
).
</paragraph>
<paragraph id="8BDB2454FFBEFFFCEC1D3783D7A2FCEA" blockId="19.[810,1460,144,1452]" pageId="19" pageNumber="20">
Despite being damaged and compressed, several elements of the specimen assigned to
<taxonomicName id="4C645FD7FFBEFFFCEB6137E0D0C5FE52" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1081,1252,457,481]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBEFFFCEB6137E0D0C5FE52" box="[1081,1252,457,481]" italics="true" pageId="19" pageNumber="20">Ymboirana acrux</emphasis>
</taxonomicName>
are still articulated, including some vertebrae, but the skull bones and some ver - tebrae at the middle portion of the fossil are scattered (i.e. not aligned with the rest of the vertebral column). In this scenario, it is plausible that the fragmented condition of some elements oc - curred during the ‘bloat and float’ stage, whereas the presence of still articulated elements could be related to the low intensity of transport events between death and deposition of the remains. Additionally, the scattered vertebrae at the central portion of the specimen may be related to reworking made by scavengers or abdominal rupture, one of the most common causes of local - ized disarticulation (see:
<bibRefCitation id="EFF559A5FFBEFFFCEB76350BD133FC89" author="McNamara ME &amp; Orr PJ &amp; Manzocchi T" box="[1070,1298,802,826]" pageId="19" pageNumber="20" pagination="210 - 26" refId="ref12475" refString="McNamara ME, Orr PJ, Manzocchi T et al. Biological controls upon the physical taphonomy of exceptionally preserved salamanders from the Miocene of Rubielos de Mora, northeast Spain. Lethaia 2012; 45: 210 - 26. https: // doi. org / 10.1111 / j. 1502 * 3931.2011.00274. x" type="journal article" year="2012">
McNamara
<emphasis id="B910F846FFBEFFFCEBF0350AD0F9FC89" box="[1192,1240,802,826]" italics="true" pageId="19" pageNumber="20">et al.</emphasis>
2012
</bibRefCitation>
, and references therein).
</paragraph>
<paragraph id="8BDB2454FFBEFFFCEC1D3548D155FA1F" blockId="19.[810,1460,144,1452]" pageId="19" pageNumber="20">
The identification of
<taxonomicName id="4C645FD7FFBEFFFCEB7B3549D0ECFCCB" authority="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher, 2024" authorityName="Santos &amp; Wilkinson &amp; Ribeiro &amp; Carvalho &amp; Zaher" authorityYear="2024" box="[1059,1229,864,888]" class="Amphibia" family="Typhlonectidae" genus="Ymboirana" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="species" species="acrux">
<emphasis id="B910F846FFBEFFFCEB7B3549D0ECFCCB" box="[1059,1229,864,888]" italics="true" pageId="19" pageNumber="20">Ymboirana acrux</emphasis>
</taxonomicName>
as a representative of
<taxonomicName id="4C645FD7FFBEFFFCEC7235A9D7E8FC2B" authorityName="Taylor" authorityYear="1968" box="[810,969,896,920]" class="Amphibia" family="Typhlonectidae" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="family">Typhlonectidae</taxonomicName>
, a group traditionally known by their aquatic or semi -aquatic behaviour, is another piece of evidence corrobor - ating the taphonomic interpretation here proposed. Regarding extant typhlonectids, species of
<taxonomicName id="4C645FD7FFBEFFFCEBC835F7D13FFC45" baseAuthorityName="Wilkinson and Nussbaum" baseAuthorityYear="1999" box="[1168,1310,990,1014]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="genus">
<emphasis id="B910F846FFBEFFFCEBC835F7D13FFC45" box="[1168,1310,990,1014]" italics="true" pageId="19" pageNumber="20">Chthonerpeton</emphasis>
</taxonomicName>
were usually considered to be less adapted to the aquatic environment, and have been found in wet soil as well as in rivers, small ponds, and flocked marshes (
<bibRefCitation id="EFF559A5FFBEFFFCEC833215D072FBE7" author="Taylor EH" box="[987,1107,1084,1108]" pageId="19" pageNumber="20" refId="ref13564" refString="Taylor EH. Ne Caecilians of the World: a Taxonomic Review. Lawrence: University of Kansas Press, 1968." type="book" year="1968">Taylor 1968</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBEFFFCEB063215D0FFFBE7" author="Tanner K" box="[1118,1246,1084,1108]" pageId="19" pageNumber="20" pagination="91 - 100" refId="ref13538" refString="Tanner K. Notizen zur Pflege und zum Verhalten einiger Blindwuhlen (Amphibia: Gymnophiona). Salamandra 1971; 7: 91 - 100." type="journal article" year="1971">Tanner 1971</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBEFFFCEBB13215D18CFBE7" author="Gudynas E &amp; Williams JD &amp; Azpelicueta M" box="[1257,1453,1084,1108]" pageId="19" pageNumber="20" pagination="5 - 28" refId="ref11810" refString="Gudynas E, Williams JD, Azpelicueta M. Morphology, ecology and biogeography of the South American caecilian Chthonerpeton indistinctum (Amphibia: Gymnophiona: Typhlonectidae). Zoologische Mededelingen 1988; 62: 5 - 28." type="journal article" year="1988">
Gudynas
<emphasis id="B910F846FFBEFFFCEA103214D157FBE7" box="[1352,1398,1084,1108]" italics="true" pageId="19" pageNumber="20">et al.</emphasis>
1988
</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBEFFFCEC723272D7CCFBC0" author="Da Silva HR" box="[810,1005,1115,1139]" pageId="19" pageNumber="20" pagination="1 - 11" refId="ref11417" refString="Da Silva HR, de Britto * Pereira MC, Caramaschi U. A new species of Chthonerpeton (Amphibia: Gymnophiona: Typhlonectidae) from Bahia, Brazil. Zootaxa 2003; 381: 1 - 11. https: // doi. org / 10.11646 / zootaxa. 381.1.1" type="journal article" year="2003">
da Silva
<emphasis id="B910F846FFBEFFFCECDA3275D792FBC0" box="[898,947,1115,1139]" italics="true" pageId="19" pageNumber="20">et al.</emphasis>
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; M.W. personal observation).
<taxonomicName id="4C645FD7FFBEFFFCEA7D3272D781FB21" baseAuthorityName="Reinhardt &amp; Lutken" baseAuthorityYear="1862" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="species" species="indistinctum">
<emphasis id="B910F846FFBEFFFCEA7D3272D781FB21" italics="true" pageId="19" pageNumber="20">Chthonerpeton indistinctum</emphasis>
</taxonomicName>
and
<taxonomicName id="4C645FD7FFBEFFFCEC823252D07EFB21" authorityName="Silva, Britto-Pereira &amp; Caramaschi" authorityYear="2003" box="[986,1119,1147,1170]" class="Amphibia" family="Typhlonectidae" genus="Chthonerpeton" kingdom="Animalia" order="Gymnophiona" pageId="19" pageNumber="20" phylum="Chordata" rank="species" species="noctinectes">
<emphasis id="B910F846FFBEFFFCEC823252D7CAFB21" box="[986,1003,1147,1170]" italics="true" pageId="19" pageNumber="20">C</emphasis>
.
<emphasis id="B910F846FFBEFFFCECA23252D07EFB21" box="[1018,1119,1147,1170]" italics="true" pageId="19" pageNumber="20">noctinectes</emphasis>
</taxonomicName>
have been kept in aquaria, sug - gesting that representatives of this genus are indeed well adapted to freshwater environments too (Barrio 1969,
<bibRefCitation id="EFF559A5FFBEFFFCEBB73290D182FB62" author="Da Silva HR" box="[1263,1443,1209,1233]" pageId="19" pageNumber="20" pagination="1 - 11" refId="ref11417" refString="Da Silva HR, de Britto * Pereira MC, Caramaschi U. A new species of Chthonerpeton (Amphibia: Gymnophiona: Typhlonectidae) from Bahia, Brazil. Zootaxa 2003; 381: 1 - 11. https: // doi. org / 10.11646 / zootaxa. 381.1.1" type="journal article" year="2003">
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). The remaining extant typhlonectid taxa are more adapted to a fully obligate aquatic lifestyle (e.g.
<bibRefCitation id="EFF559A5FFBEFFFCEB3A32D1D18CFAA3" author="Wilkinson M &amp; Nussbaum RA" box="[1122,1453,1272,1296]" pageId="19" pageNumber="20" pagination="39 - 109" refId="ref14053" refString="Wilkinson M, Nussbaum RA. Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae). Biological Journal of the Linnean Societo 1997; 62: 39 - 109. https: // doi. org / 10.1111 / j. 1095 * 8312.1997. tb 01616. x" type="journal article" year="1997">Wilkinson and Nussbaum 1997</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBEFFFCEC72333ED016FA9C" author="Gorzula S &amp; Senaris JC" box="[810,1079,1303,1327]" pageId="19" pageNumber="20" pagination="1 - 270" refId="ref11715" refString="Gorzula S, Senaris JC. Contribution to the herpetofauna of the Venezuelan Guayana I A database. Scientia Guaiane 1998; 8: 1 - 270." type="journal article" year="1998">Gorzula and Señaris 1998</bibRefCitation>
,
<bibRefCitation id="EFF559A5FFBEFFFCEB1D333ED14EFA9C" author="Maciel AO &amp; Hoogmoed MS" box="[1093,1391,1303,1327]" pageId="19" pageNumber="20" pagination="1 - 53" refId="ref12283" refString="Maciel AO, Hoogmoed MS. Taxonomy and distribution of caecilian am * phibians (Gymnophiona) of Brazilian Amazonia, with a key to their identification. Zootaxa 2011; 2984: 1 - 53. https: // doi. org / 10.11646 / zootaxa. 2984.1.1" type="journal article" year="2011">Maciel and Hoogmoed 2011</bibRefCitation>
). This finding also corroborates the hypothesis proposed by Barcelos and Santos (2023), who suggested that the fossil record of am - phibians (including caecilians) in South America may be biased favouring the preservation of aquatic and well -ossified taxa.
</paragraph>
</subSubSection>
</treatment>
</document>
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