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<document id="C0667FB8A6285E2DC3D1ACC5F6F14B1D" ID-CLB-Dataset="3066" ID-DOI="10.5252/geodiversitas2021v43a23" ID-GBIF-Dataset="8bc2657c-1d54-4780-88d2-7f10c5f868a8" ID-ISSN="1638-9395" ID-Zenodo-Dep="5764679" ID-ZooBank="urn:lsid:zoobank.org:pub:46B11D2C-7A6E-489F-AAF6-223919C61A23" IM.materialsCitations_approvedBy="felipe" IM.metadata_approvedBy="felipe" IM.tables_requiresApprovalFor="existingObjects,plazi" IM.taxonomicNames_approvedBy="felipe" checkinTime="1638893719025" checkinUser="felipe" docAuthor="Wu, Feixiang, Chang, Mee-Mann &amp; Janvier, Philippe" docDate="2021" docId="039887B1F5180930FCDAF895FAFBCD0A" docLanguage="en" docName="Geodiversitas.43.23.1293-1307.pdf" docOrigin="Geodiversitas 43 (23)" docStyle="DocumentStyle:F830B10FF475E64C1F1601E3B32DDC00.4:Geodiversitas.2018-.journal_article" docStyleId="F830B10FF475E64C1F1601E3B32DDC00" docStyleName="Geodiversitas.2018-.journal_article" docStyleVersion="4" docTitle="Mesomyzon mengae Chang, Zhang &amp; Miao 2006" docType="treatment" docVersion="7" lastPageNumber="1300" masterDocId="FFA1FFC9F51B0939FF86FFC7FF97CC78" masterDocTitle="A new look at the Cretaceous Lamprey Mesomyzon Chang, Zhang &amp; Miao, 2006 from the Jehol Biota" masterLastPageNumber="1307" masterPageNumber="1293" pageNumber="1294" updateTime="1699472073411" updateUser="ExternalLinkService" zenodo-license-document="CC0-1.0" zenodo-license-figures="CC0-1.0">
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<mods:title id="6FAD15933AE4000E49264C0CE61A5F1D">A new look at the Cretaceous Lamprey Mesomyzon Chang, Zhang &amp; Miao, 2006 from the Jehol Biota</mods:title>
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<mods:namePart id="B84790E58D43953BA92197174063BFD4">Wu, Feixiang</mods:namePart>
<mods:affiliation id="66AFA36E19C3F59E002BC744664259DD">Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences &amp; Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences Beijing 100044 (China) and CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044 (China)</mods:affiliation>
<mods:nameIdentifier id="D2868D3175254A9E217B11E34F9E7C9A" type="email">wufeixiang@ivpp.ac.cn</mods:nameIdentifier>
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<mods:namePart id="8EBCA5E3CF839B8402DB4798AB793B10">Chang, Mee-Mann</mods:namePart>
<mods:affiliation id="E598C2C0D308D511E6F0C226B8FD77DE">Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences &amp; Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences Beijing 100044 (China) and CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044 (China)</mods:affiliation>
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<mods:namePart id="D6E94862CAE97F971B7136E903D9AC43">Janvier, Philippe</mods:namePart>
<mods:affiliation id="5D041BFA1D4A7FFC05188EAA82078054">Sorbonne Université (CR 2 P - MNHN, CNRS, UPMC-Paris 6). Muséum national d’Histoire naturelle, Département Origine et Évolution. case postale 38, 57 rue Cuvier, 75231 Paris cedex 05 (France)</mods:affiliation>
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<mods:title id="9083342174CCA255486924ABBEFAD2CC">Geodiversitas</mods:title>
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<mods:date id="F797C98C467C91F4C0D6794FC6AD081F">2021</mods:date>
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<mods:number id="DF56661EC91785228BEE080373ED93B9">2021-11-25</mods:number>
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<treatment id="039887B1F5180930FCDAF895FAFBCD0A" ID-DOI="http://doi.org/10.5281/zenodo.5767838" ID-GBIF-Taxon="191256377" ID-Zenodo-Dep="5767838" LSID="urn:lsid:plazi:treatment:039887B1F5180930FCDAF895FAFBCD0A" httpUri="http://treatment.plazi.org/id/039887B1F5180930FCDAF895FAFBCD0A" lastPageId="9" lastPageNumber="1300" pageId="3" pageNumber="1294">
<subSubSection id="C32B652CF518093AFCDAF895FA17CB13" box="[860,1408,1873,1900]" pageId="3" pageNumber="1294" type="nomenclature">
<paragraph id="8B8E36A7F518093AFCDAF895FA17CB13" blockId="3.[860,1408,1873,1932]" box="[860,1408,1873,1900]" pageId="3" pageNumber="1294">
<taxonomicName id="4C314D24F518093AFCDAF895FA17CB13" authority="Chang, Zhang &amp; Miao, 2006" authorityName="Chang, Zhang &amp; Miao" authorityYear="2006" box="[860,1408,1873,1900]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="3" pageNumber="1294" phylum="Chordata" rank="species" species="mengae">
<emphasis id="B945EAB5F518093AFCDAF895FBADCB14" bold="true" box="[860,1082,1874,1900]" italics="true" pageId="3" pageNumber="1294">Mesomyzon mengae</emphasis>
<bibRefCitation id="EFA04B56F518093AFBC7F896FA17CB13" author="CHANG M. - M. &amp; ZHANG J. Y. &amp; MIAO D. S." box="[1089,1408,1873,1900]" pageId="3" pageNumber="1294" pagination="972 - 974" refId="ref11511" refString="CHANG M. - M., ZHANG J. Y. &amp; MIAO D. S. 2006. - A lamprey from the Cretaceous Jehol biota of China. Nature 441: 972 - 974. https: // doi. org / 10.1038 / nature 04730" type="journal article" year="2006">Chang, Zhang &amp; Miao, 2006</bibRefCitation>
</taxonomicName>
</paragraph>
</subSubSection>
<subSubSection id="C32B652CF518093AFBBCF8B6FB35CBF4" box="[1082,1186,1905,1932]" pageId="3" pageNumber="1294" type="description">
<paragraph id="8B8E36A7F518093AFBBCF8B6FB35CBF4" blockId="3.[860,1408,1873,1932]" box="[1082,1186,1905,1932]" pageId="3" pageNumber="1294">
(
<figureCitation id="130A2A22F518093AFBC4F8B6FB0ECBF3" box="[1090,1177,1905,1932]" captionStart-0="FIG" captionStart-1="FIG" captionStart-2="FIG" captionStartId-0="8.[132,143,1381,1399]" captionStartId-1="10.[132,143,1619,1637]" captionStartId-2="12.[132,143,1917,1935]" captionTargetBox-0="[132,1455,215,1322]" captionTargetBox-1="[132,1456,243,1562]" captionTargetBox-2="[136,1451,217,1872]" captionTargetId-0="figure-353@8.[132,1455,214,1339]" captionTargetId-1="figure-116@10.[132,1458,242,1565]" captionTargetId-2="figure-24@12.[136,1451,219,1873]" captionTargetPageId-0="8" captionTargetPageId-1="10" captionTargetPageId-2="12" captionText-0="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." captionText-1="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." captionText-2="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi-0="http://doi.org/10.5281/zenodo.5764681" figureDoi-1="http://doi.org/10.5281/zenodo.5764683" figureDoi-2="http://doi.org/10.5281/zenodo.5764685" httpUri-0="https://zenodo.org/record/5764681/files/figure.png" httpUri-1="https://zenodo.org/record/5764683/files/figure.png" httpUri-2="https://zenodo.org/record/5764685/files/figure.png" pageId="3" pageNumber="1294">Figs 2-4</figureCitation>
)
</paragraph>
</subSubSection>
<subSubSection id="C32B652CF518093DFCABF87EFD32CDC1" lastPageId="4" lastPageNumber="1295" pageId="3" pageNumber="1294" type="materials_examined">
<paragraph id="8B8E36A7F518093DFCABF87EFD32CDC1" blockId="3.[813,1457,1976,2027]" lastBlockId="4.[132,776,216,441]" lastPageId="4" lastPageNumber="1295" pageId="3" pageNumber="1294">
<materialsCitation id="3B593CFAF518093DFCABF87EFD36CDC1" ID-GBIF-Occurrence="3416549301" accessionNumber="V14719" country="China" county="Yongyin County" lastPageId="4" lastPageNumber="1295" location="Institute of Vertebrate Paleontology" municipality="Paleoanthropology" pageId="3" pageNumber="1294" specimenCount="1" stateProvince="Beijing" typeStatus="holotype">
<typeStatus id="548A8805F518093AFCABF87EFC0DCBB7" box="[813,922,1977,2000]" pageId="3" pageNumber="1294" type="holotype">HOLOTYPE</typeStatus>
. — IVPP (
<location id="8EEE607CF518093AFB97F87FFA16CBA8" LSID="urn:lsid:plazi:treatment:039887B1F5180930FCDAF895FAFBCD0A:8EEE607CF518093AFB97F87FFA16CBA8" box="[1041,1409,1976,2000]" country="China" municipality="Paleoanthropology" name="Institute of Vertebrate Paleontology" pageId="3" pageNumber="1294" stateProvince="Beijing">Institute of Vertebrate Paleontology</location>
and
<collectingMunicipality id="6BEAACDDF518093AFCA8F814FC7ECB93" box="[814,1001,2003,2027]" pageId="3" pageNumber="1294">Paleoanthropology</collectingMunicipality>
,
<collectingRegion id="49F5F845F518093AFC73F814FBA8CB93" box="[1013,1087,2003,2027]" country="China" name="Beijing" pageId="3" pageNumber="1294">Beijing</collectingRegion>
,
<collectingCountry id="F3267637F518093AFBCDF814FB1DCB93" box="[1099,1162,2003,2027]" name="China" pageId="3" pageNumber="1294">China</collectingCountry>
) collection number
<accessionNumber id="9462AB44F518093AFADFF814FA3ACB93" box="[1369,1453,2003,2027]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V14719" pageId="3" pageNumber="1294" type="EnaNcbi">V14719</accessionNumber>
, a nearly complete adult specimen, without preservation of the tail (
<bibRefCitation id="EFA04B56F51F093DFF0AFF34FEAECD73" author="CHANG M. - M. &amp; ZHANG J. Y. &amp; MIAO D. S." box="[140,313,243,267]" pageId="4" pageNumber="1295" pagination="972 - 974" refId="ref11511" refString="CHANG M. - M., ZHANG J. Y. &amp; MIAO D. S. 2006. - A lamprey from the Cretaceous Jehol biota of China. Nature 441: 972 - 974. https: // doi. org / 10.1038 / nature 04730" type="journal article" year="2006">
Chang
<emphasis id="B945EAB5F51F093DFF55FF34FE95CD73" box="[211,258,243,267]" italics="true" pageId="4" pageNumber="1295">et al.</emphasis>
2006
</bibRefCitation>
: fig. 1a). REFERRED MATERIAL. — IVPP
<accessionNumber id="9462AB44F51F093DFE20FEE5FE62CD42" box="[422,501,290,314]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V14718" pageId="4" pageNumber="1295" type="EnaNcbi">V14718</accessionNumber>
A, B (a metamorphosed individual),
<accessionNumber id="9462AB44F51F093DFF48FEFAFE8CCD2D" box="[206,283,317,341]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V14981" pageId="4" pageNumber="1295" type="EnaNcbi">V14981</accessionNumber>
A, B,
<accessionNumber id="9462AB44F51F093DFECBFEFAFE0CCD2D" box="[333,411,317,341]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15027" pageId="4" pageNumber="1295" type="EnaNcbi">V15027</accessionNumber>
A, B, V15450.3,
<accessionNumber id="9462AB44F51F093DFDB3FEFAFD15CD2D" box="[565,642,317,341]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15448" pageId="4" pageNumber="1295" type="EnaNcbi">V15448</accessionNumber>
A, B,
<accessionNumber id="9462AB44F51F093DFD35FEFAFC93CD2D" box="[691,772,317,341]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="4" pageNumber="1295" type="EnaNcbi">V15449</accessionNumber>
. HORIZON AND LOCALITY. — Yixian Formation,
<location id="8EEE607CF51F093DFDDEFEAAFC91CDFC" LSID="urn:lsid:plazi:treatment:039887B1F5180930FCDAF895FAFBCD0A:8EEE607CF51F093DFDDEFEAAFC91CDFC" box="[600,774,364,388]" name="Lower Cretaceous" pageId="4" pageNumber="1295">Lower Cretaceous</location>
(
<emphasis id="B945EAB5F51F093DFF0AFE4FFF02CDE7" box="[140,149,392,415]" italics="true" pageId="4" pageNumber="1295">c</emphasis>
. 125 Ma) (
<bibRefCitation id="EFA04B56F51F093DFE85FE40FEE5CDE7" author="ZHOU Z. H." box="[259,370,391,415]" pageId="4" pageNumber="1295" pagination="543 - 599" refId="ref13697" refString="ZHOU Z. H. 2014. - The Jehol Biota, an Early Cretaceous terrestrial Lagerstatte: new discoveries and implications. National Science Review 1: 543 - 599. https: // doi. org / 10.1093 / nsr / nwu 055" type="journal article" year="2014">Zhou 2014</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51F093DFEF8FE40FDD1CDE7" author="ZHOU Z. H. &amp; WANG Y." box="[382,582,391,415]" pageId="4" pageNumber="1295" pagination="241 - 252" refId="ref13742" refString="ZHOU Z. H. &amp; WANG Y. 2017. - Vertebrate assemblages of the Jurassic Yanliao Biota and the Early Cretaceous Jehol Biota: Comparisons and implications. Paleoword 26: 241 - 252. https: // doi. org / 10.1016 / j. palwor. 2017.01.002" type="journal article" year="2017">Zhou &amp; Wang 2017</bibRefCitation>
); Ningcheng, Inner Mongolia and
<collectingCounty id="62EF4E2BF51F093DFE95FE66FE22CDC1" box="[275,437,417,441]" pageId="4" pageNumber="1295">Yongyin County</collectingCounty>
, Hebei Province, China
</materialsCitation>
.
</paragraph>
</subSubSection>
<subSubSection id="C32B652CF51F093DFF02FE15FE1DCF5E" pageId="4" pageNumber="1295" type="diagnosis">
<paragraph id="8B8E36A7F51F093DFF02FE15FE1DCF5E" blockId="4.[131,777,465,806]" pageId="4" pageNumber="1295">
AMENDED DIAGNOSIS. — A fossil lamprey with elongated and eelshaped body, body length 12 times the maximum body depth, 4 times the head length; first gill pouch posteroventral to otic capsule; prebranchial region long, twice the maximum head height and 1.3- 1.8 times the branchial length; oral papillae large and triangular (conical); oral fimbriae numerous, maximum number presumably no less than 80; circumoral teeth series incomplete and lacking the posterior section; supraoral lamina large and bicuspid; two dorsal fins widely separated, anterior dorsal fin long and commencing above 4
<superScript id="7C449BEFF51F093DFF48FD78FF4ACEA8" attach="left" box="[206,221,703,720]" fontSize="7" pageId="4" pageNumber="1295">th</superScript>
gill pouch; ribbon-like preanal skin fold long and extending to anterior branchial region; anal fin fold present; 70-80 preanal muscular segments; preanal myomeres Z-shaped and caudal ones W-shaped; tail hypocercal.
</paragraph>
</subSubSection>
<subSubSection id="C32B652CF51F0930FF02FC91FAFBCD0A" lastPageId="9" lastPageNumber="1300" pageId="4" pageNumber="1295" type="description">
<paragraph id="8B8E36A7F51F093DFF02FC91FE82CF16" blockId="4.[130,776,854,1135]" box="[132,277,854,880]" pageId="4" pageNumber="1295">DESCRIPTION</paragraph>
<paragraph id="8B8E36A7F51F093DFF02FCB2FED9CFF7" blockId="4.[130,776,854,1135]" box="[132,334,885,911]" pageId="4" pageNumber="1295">
<emphasis id="B945EAB5F51F093DFF02FCB2FED9CFF7" box="[132,334,885,911]" italics="true" pageId="4" pageNumber="1295">General appearance</emphasis>
</paragraph>
<paragraph id="8B8E36A7F51F093DFF02FC52FD22C817" blockId="4.[130,776,854,1135]" pageId="4" pageNumber="1295">
As described byChang
<emphasis id="B945EAB5F51F093DFEF3FC51FE32CFD7" box="[373,421,917,943]" italics="true" pageId="4" pageNumber="1295">et al.</emphasis>
(2006),
<taxonomicName id="4C314D24F51F093DFE7BFC51FDE5CFD7" authorityName="Chang, Zhang &amp; Miao" authorityYear="2006" box="[509,626,918,943]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="4" pageNumber="1295" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51F093DFE7BFC51FDE5CFD7" box="[509,626,918,943]" italics="true" pageId="4" pageNumber="1295">Mesomyzon</emphasis>
</taxonomicName>
has an eel-like body and lacks paired fins. The adult individuals described here are larger than the
<typeStatus id="548A8805F51F093DFEF9FC13FE49CF96" box="[383,478,980,1006]" pageId="4" pageNumber="1295" type="holotype">holotype</typeStatus>
(
<tableCitation id="C6B3031CF51F093DFE6AFC13FDADCF97" box="[492,570,980,1007]" captionStart="TABLE" captionStartId="7.[132,143,219,237]" captionTargetPageId="7" captionText="TABLE 1. — Meristic measurements of Mesomyzon mengae Chang, Zhang &amp; Miao, 2006. Abbreviations and interpretations: a, cloacal slit length; a-C, tail length; d, oral disc length;d-O, preorbital length (from anteriormost internal edge of oral disc to anterior edge of eye); d-B1, prebranchial length or head length;d-n, snout length (narial opening not well-preserved, measured between anterior edge of naso-hypophysial organ to anteriormost internal edge of oral disc); B1-B2, interbranchial opening length; B1-B7, branchial length; B7-a, trunk length; Hh, head height (measured at the level of posterior edge of eye); I, interocular length; O, eye length; O-B1, postocular length; TL, total length." httpUri="http://table.plazi.org/id/DF4E662FF51C093EFF02FF1CFD8FCD30" pageId="4" pageNumber="1295" tableUuid="DF4E662FF51C093EFF02FF1CFD8FCD30">Table 1</tableCitation>
). They have a welldeveloped oral disc and a long prebranchial region. The new materials here show that the anterior dorsal fin is very long and the ventral midline of the trunk is fringed with a ribbonlike preanal skin fold. The tail is hypocercal (
<figureCitation id="130A2A22F51F093DFDE1FB93FD32C816" box="[615,677,1108,1134]" captionStart="FIG" captionStartId="8.[132,143,1381,1399]" captionTargetBox="[132,1455,215,1322]" captionTargetId="figure-353@8.[132,1455,214,1339]" captionTargetPageId="8" captionText="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="4" pageNumber="1295">Fig. 2</figureCitation>
).
</paragraph>
<paragraph id="8B8E36A7F51F093DFF02FB53FF2BC8D6" blockId="4.[132,188,1172,1198]" box="[132,188,1172,1198]" pageId="4" pageNumber="1295">
<heading id="D0C681CBF51F093DFF02FB53FF2BC8D6" box="[132,188,1172,1198]" fontSize="11" level="2" pageId="4" pageNumber="1295" reason="8">
<emphasis id="B945EAB5F51F093DFF02FB53FF2BC8D6" box="[132,188,1172,1198]" italics="true" pageId="4" pageNumber="1295">Head</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F51F093DFF02FB73FE5CCB54" blockId="4.[130,777,1204,2028]" pageId="4" pageNumber="1295">
The cranial cartilages are preserved in imprints in some specimens. Here we follow
<bibRefCitation id="EFA04B56F51F093DFE3FFB13FD40C896" author="HARDISTY M. W. &amp; POTTER I. C." box="[441,727,1236,1262]" pageId="4" pageNumber="1295" pagination="118 - 124" refId="ref11958" refString="HARDISTY M. W. &amp; POTTER I. C. 1981. - The skeleton, in The biology of lampreys. in HARDISTY M. W. &amp; POTTER I. C. (eds), The Biology of Lampreys. Volume 3. Academic Press, New York: 118 - 124." type="book chapter" year="1981">Hardisty &amp; Potter (1981)</bibRefCitation>
and De Iluiis &amp; Pulerà (2011) for the terminology of the cranial cartilages referred below. The main parts of the anterior and posterior dorsal cartilages, and the anterior lateral cartilage can be delineated (
<figureCitation id="130A2A22F51F093DFEDEFA94FE0CC915" box="[344,411,1363,1389]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3</figureCitation>
A-D; 4A-C). The anterior lateral cartilage is situated ventrolaterally to the front part of the anterior dorsal cartilage and is tapering in the ventral part. The anterior dorsal cartilage is wider in the hind part than in the front, whose lateral margin is flared backward into a posterolateral angle. The posterior limit of the anterior dorsal cartilage terminates at the level very close to the external narial opening. The posterior dorsal cartilage is wider than the anterior dorsal cartilage and overlaps the latter posteriorly as in living lampreys (
<figureCitation id="130A2A22F51F093DFED5F9B5FE34CAF5" box="[339,419,1650,1677]" captionStart="FIG" captionStartId="6.[132,143,1916,1934]" captionTargetId="figure-32@6.[698,1267,769,1325]" captionTargetPageId="6" captionText="FIG. 1. — Generalized anatomy of living lampreys: A, schematic sagittal section through head and pharyngeal region; the vessels, esophagus, respiratory tube, and parts of the heart are shown with portions cut away, rather than in sagittal section; redrawn after De Iuliis &amp; Pulerà 2011, with the structures of the nasohypophysial complex labelled after Janvier 1974; B, the cranial skeleton of an adult lamprey, redrawn after Hardisty &amp; Potter 1981; C, arrangement pattern of the cranial nerves, redrawn after Marinelli &amp; Strenger 1954; D, oral disc of an adult lamprey showing the keratinous teeth and other associated structures. The dotted lines delineate the various fields. Redrawn after Renaud 2011." figureDoi="http://doi.org/10.5281/zenodo.5767846" httpUri="https://zenodo.org/record/5767846/files/figure.png" pageId="4" pageNumber="1295">Fig. 1B</figureCitation>
) (
<bibRefCitation id="EFA04B56F51F093DFE3CF9B5FD2BCAF4" author="HARDISTY M. W. &amp; POTTER I. C." box="[442,700,1650,1677]" pageId="4" pageNumber="1295" pagination="118 - 124" refId="ref11958" refString="HARDISTY M. W. &amp; POTTER I. C. 1981. - The skeleton, in The biology of lampreys. in HARDISTY M. W. &amp; POTTER I. C. (eds), The Biology of Lampreys. Volume 3. Academic Press, New York: 118 - 124." type="book chapter" year="1981">Hardisty &amp; Potter 1981</bibRefCitation>
: fig. 4;
<bibRefCitation id="EFA04B56F51F093DFF02F955FE25CAD5" author="MARINELLI W. &amp; STRENGER A." box="[132,434,1682,1709]" pageId="4" pageNumber="1295" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger, 1954</bibRefCitation>
: (figs 24, 51a). There is a joint occasionally preserved in the fossils along the dorsal edge of the snout region (some distance in front of the eyes) (
<figureCitation id="130A2A22F51F093DFD37F915FF0ECB74" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3B, C</figureCitation>
;
<figureCitation id="130A2A22F51F093DFF25F935FF53CB74" box="[163,196,1778,1804]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="4" pageNumber="1295">4A</figureCitation>
) which might indicate the differentiation of the anterior dorsal and posterior cartilages.
</paragraph>
<paragraph id="8B8E36A7F51F093DFF1DF8F5FC90CB93" blockId="4.[130,777,1204,2028]" pageId="4" pageNumber="1295">
To the rear of the posterior dorsal cartilage there is a notable dark imprint which is nearly vertically arranged immediately in front of the eye (
<figureCitation id="130A2A22F51F093DFEAFF8B6FE04CBF4" box="[297,403,1905,1932]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3A, B</figureCitation>
;
<figureCitation id="130A2A22F51F093DFE1FF8B6FE29CBF4" box="[409,446,1905,1932]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="4" pageNumber="1295">4A</figureCitation>
). This may represent the anterior pillar of the subocular arch (
<figureCitation id="130A2A22F51F093DFE2AF856FE6ACBD4" box="[428,509,1937,1964]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3B</figureCitation>
;
<figureCitation id="130A2A22F51F093DFD8EF856FDBFCBD3" box="[520,552,1937,1963]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="4" pageNumber="1295">4A</figureCitation>
) to form the anterior part of the orbital cavity as in living lampreys (
<bibRefCitation id="EFA04B56F51F093DFDF2F876FD68CBB3" author="JOHNELS A. G." box="[628,767,1969,1995]" pageId="4" pageNumber="1295" pagination="139 - 279" refId="ref12330" refString="JOHNELS A. G. 1948. - On the development and morphology of the skeleton of the head of Petromyzon. Acta Zoologica 29: 139 - 279. https: // doi. org / 10.1111 / j. 1463 - 6395.1948. tb 00030. x" type="journal article" year="1948">Johnels 1948</bibRefCitation>
: fig. 57;
<bibRefCitation id="EFA04B56F51F093DFF57F816FE5ACB93" author="HARDISTY M. W. &amp; POTTER I. C." box="[209,461,2001,2028]" pageId="4" pageNumber="1295" pagination="118 - 124" refId="ref11958" refString="HARDISTY M. W. &amp; POTTER I. C. 1981. - The skeleton, in The biology of lampreys. in HARDISTY M. W. &amp; POTTER I. C. (eds), The Biology of Lampreys. Volume 3. Academic Press, New York: 118 - 124." type="book chapter" year="1981">Hardisty &amp; Potter 1981</bibRefCitation>
: fig. 4;
<bibRefCitation id="EFA04B56F51F093DFD9FF816FD37CB93" author="JANVIER P." box="[537,672,2001,2027]" pageId="4" pageNumber="1295" pagination="131 - 188" refId="ref12070" refString="JANVIER P. 1993. - Patterns of diversity in the skull of jawless fishes, in HANKEN J. &amp; HALL B. K. (eds), The Skull. University of Chicago Press, Chicago: 131 - 188." type="book chapter" year="1993">
<date id="FF8F1067F51F093DFD9FF816FD37CB93" box="[537,672,2001,2027]" pageId="4" pageNumber="1295" value="1993-01">Janvier 1993</date>
</bibRefCitation>
: fig. 4.4).
</paragraph>
<paragraph id="8B8E36A7F51F093DFCC4FF10FB5CC8F7" blockId="4.[810,1458,215,1167]" pageId="4" pageNumber="1295">
The imprints of the styliform cartilage is preserved posteroventral to the otic capsule (
<figureCitation id="130A2A22F51F093DFBD8FF30FB0ACD69" box="[1118,1181,247,273]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3</figureCitation>
A-D; 4A). It extends posteroventrally towards the pharynx as its counterpart in living forms (
<bibRefCitation id="EFA04B56F51F093DFCFEFEF0FBE5CD29" author="HARDISTY M. W. &amp; POTTER I. C." box="[888,1138,311,337]" pageId="4" pageNumber="1295" pagination="118 - 124" refId="ref11958" refString="HARDISTY M. W. &amp; POTTER I. C. 1981. - The skeleton, in The biology of lampreys. in HARDISTY M. W. &amp; POTTER I. C. (eds), The Biology of Lampreys. Volume 3. Academic Press, New York: 118 - 124." type="book chapter" year="1981">Hardisty &amp; Potter 1981</bibRefCitation>
: fig. 4). It is linked to the velar skeleton by small muscles in modern lampreys (
<bibRefCitation id="EFA04B56F51F093DFA9CFE90FA08CD09" author="JANVIER P." box="[1306,1439,343,369]" pageId="4" pageNumber="1295" pagination="131 - 188" refId="ref12070" refString="JANVIER P. 1993. - Patterns of diversity in the skull of jawless fishes, in HANKEN J. &amp; HALL B. K. (eds), The Skull. University of Chicago Press, Chicago: 131 - 188." type="book chapter" year="1993">
<date id="FF8F1067F51F093DFA9CFE90FA08CD09" box="[1306,1439,343,369]" pageId="4" pageNumber="1295" value="1993-01">Janvier 1993</date>
</bibRefCitation>
). The structures of the naso-hypophysial complex is wellpreserved in IVPP
<accessionNumber id="9462AB44F51F093DFC7EFE50FBCFCDC9" box="[1016,1112,406,433]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="4" pageNumber="1295" type="EnaNcbi">V 15449</accessionNumber>
and V 15450.3, with the olfactory organ’s left side exposed in the former and the dorsal aspect in the latter (
<figureCitation id="130A2A22F51F093DFB83FE11FBD1CD88" box="[1029,1094,470,496]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3</figureCitation>
C-F; 4B, F). It is enclosed within the imprints of the nasal sac, which is located in the midline and just anterodorsally to the eyes and likely independent from the cranial cartilages. The olfactory organ is preserved in a way that it partly overlaps the naso-hypophysial atrium in IVPP
<accessionNumber id="9462AB44F51F093DFC09FDB1FC66CEE9" box="[911,1009,630,657]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="4" pageNumber="1295" type="EnaNcbi">V 15449</accessionNumber>
(
<figureCitation id="130A2A22F51F093DFB84FDB1FBE8CEE8" box="[1026,1151,630,656]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3C, D</figureCitation>
;
<figureCitation id="130A2A22F51F093DFB09FDB1FB38CEE8" box="[1167,1199,630,656]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="4" pageNumber="1295">4B</figureCitation>
). The preserved part of this organ bears eight folds in IVPP
<accessionNumber id="9462AB44F51F093DFB46FD51FAB5CEC8" box="[1216,1314,661,688]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="4" pageNumber="1295" type="EnaNcbi">V 15449</accessionNumber>
(dorsolateral view) (
<figureCitation id="130A2A22F51F093DFCF1FD72FC66CEA8" box="[887,1009,693,720]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3C, D</figureCitation>
;
<figureCitation id="130A2A22F51F093DFC78FD71FB89CEA8" box="[1022,1054,694,720]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="4" pageNumber="1295">4B</figureCitation>
) and six parallel and evenly arranged folds in IVPP V 15450.3 (dorsal view) (
<figureCitation id="130A2A22F51F093DFB5FFD12FAD0CE88" box="[1241,1351,725,752]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3E, F</figureCitation>
;
<figureCitation id="130A2A22F51F093DFAD4FD11FAE4CE88" box="[1362,1395,726,752]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="4" pageNumber="1295">4F</figureCitation>
). The naso-hypophysial duct extends anterodorsally for a length that approximates that of the short axis of the eye to the naris, which is dorsally positioned without a depression surrounding itself as in living lampreys (
<bibRefCitation id="EFA04B56F51F093DFB90FC92FB09CF17" author="JANVIER P." box="[1046,1182,853,879]" pageId="4" pageNumber="1295" pagination="193 - 200" refId="ref12015" refString="JANVIER P. 1974. - The structure of the naso-hypophysial complex and the mouth in fossil and extant cyclostomes, with remarks on amphiaspiforms. Zoologica Scripta, Stockholm 3: 193 - 200. https: // doi. org / 10.1111 / j. 1463 - 6409.1974. tb 00816. x" type="journal article" year="1974">
<date id="FF8F1067F51F093DFB90FC92FB09CF17" box="[1046,1182,853,879]" pageId="4" pageNumber="1295" value="1974-01">Janvier 1974</date>
</bibRefCitation>
). The hypophysial pouch (tube) (
<figureCitation id="130A2A22F51F093DFCF8FCB2FC6FCFF7" box="[894,1016,885,911]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3C, D</figureCitation>
;
<figureCitation id="130A2A22F51F093DFB85FCB2FBB2CFF7" box="[1027,1061,885,911]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="4" pageNumber="1295">4B</figureCitation>
), a blind-ending structure serving to pump water into and out of the naso-hypophysial atrium (
<bibRefCitation id="EFA04B56F51F093DFCB0FC72FC28CFB7" author="JANVIER P." box="[822,959,949,975]" pageId="4" pageNumber="1295" pagination="193 - 200" refId="ref12015" refString="JANVIER P. 1974. - The structure of the naso-hypophysial complex and the mouth in fossil and extant cyclostomes, with remarks on amphiaspiforms. Zoologica Scripta, Stockholm 3: 193 - 200. https: // doi. org / 10.1111 / j. 1463 - 6409.1974. tb 00816. x" type="journal article" year="1974">
<date id="FF8F1067F51F093DFCB0FC72FC28CFB7" box="[822,959,949,975]" pageId="4" pageNumber="1295" value="1974-01">Janvier 1974</date>
</bibRefCitation>
), extends posteroventrally from the bottom of the olfactory organtowards the pharynx, and bends downward abruptly when it approaches the branchial apparatus. It must have extended more posteriorly, as its rear is covered by the gill structures in IVPP
<accessionNumber id="9462AB44F51F093DFC7FFBF2FBCAC837" box="[1017,1117,1076,1103]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="4" pageNumber="1295" type="EnaNcbi">V 15449</accessionNumber>
. The region of the pineal organ cannot be clearly distinguished as it is blurred by a patch of dark matter above the olfactory organ.
</paragraph>
<paragraph id="8B8E36A7F51F093DFCABFB72FBBCC8B6" blockId="4.[813,1067,1204,1230]" box="[813,1067,1204,1230]" pageId="4" pageNumber="1295">
<heading id="D0C681CBF51F093DFCABFB72FBBCC8B6" box="[813,1067,1204,1230]" fontSize="11" level="2" pageId="4" pageNumber="1295" reason="8">
<emphasis id="B945EAB5F51F093DFCABFB72FBBCC8B6" box="[813,1067,1204,1230]" italics="true" pageId="4" pageNumber="1295">Brain and cranial nerves</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F51F093DFCABFB13FAC7CB34" blockId="4.[811,1457,1235,1868]" pageId="4" pageNumber="1295">
(IVPP V15450.3): The remnants of the brain are represented by a patch of coarse sediments in IVPP V 15450.3 (
<figureCitation id="130A2A22F51F093DFADEFB34FCA8C956" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="4" pageNumber="1295">Figs 3E, F</figureCitation>
;
<figureCitation id="130A2A22F51F093DFCCAFAD3FCFAC956" box="[844,877,1300,1326]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="4" pageNumber="1295">4F</figureCitation>
). Based on the position of the roots of some cranial nerves and their arrangement in living lamprey (
<figureCitation id="130A2A22F51F093DFACDFAF4FA36C935" box="[1355,1441,1331,1357]" captionStart="FIG" captionStartId="6.[132,143,1916,1934]" captionTargetId="figure-32@6.[698,1267,769,1325]" captionTargetPageId="6" captionText="FIG. 1. — Generalized anatomy of living lampreys: A, schematic sagittal section through head and pharyngeal region; the vessels, esophagus, respiratory tube, and parts of the heart are shown with portions cut away, rather than in sagittal section; redrawn after De Iuliis &amp; Pulerà 2011, with the structures of the nasohypophysial complex labelled after Janvier 1974; B, the cranial skeleton of an adult lamprey, redrawn after Hardisty &amp; Potter 1981; C, arrangement pattern of the cranial nerves, redrawn after Marinelli &amp; Strenger 1954; D, oral disc of an adult lamprey showing the keratinous teeth and other associated structures. The dotted lines delineate the various fields. Redrawn after Renaud 2011." figureDoi="http://doi.org/10.5281/zenodo.5767846" httpUri="https://zenodo.org/record/5767846/files/figure.png" pageId="4" pageNumber="1295">Fig. 1C</figureCitation>
), the major divisions of the brain can be roughly recognized. The paired olfactory nerves can be roughly discerned, which contact anteriorly with the hind part of the nasal sac. The posterior part of the telencephalon is rounded and terminated at the level of the posterior rim of the eyes. After exiting from the braincase, the trigeminus ophthalmicus profundus (V
<subScript id="17B534E2F51F093DFCCFF9D8FCC4CA48" attach="left" box="[841,851,1567,1584]" fontSize="7" pageId="4" pageNumber="1295">1</subScript>
) extends above the eyes and branches off to innervate the annular muscles of the oral disc. The buccal ramus of the facial nerve (VII.buc) exits below the eyes and extends anteriorly to be convergent with the V
<subScript id="17B534E2F51F093DFB40F9B8FB47CAE8" attach="left" box="[1222,1232,1663,1680]" fontSize="7" pageId="4" pageNumber="1295">1</subScript>
toward the oral disc. The recurrent rami of the facial nerve are well preserved
<emphasis id="B945EAB5F51F093DFA1DF954FCC5CAB4" italics="true" pageId="4" pageNumber="1295">in situ</emphasis>
, and originally surround the otic capsules. The labyrinth membrane cannot be detected in our materials. The glossophyngeus (IX) and vagus (X) nerves are also arranged in a pattern that is almost identical to that in living lampreys (
<figureCitation id="130A2A22F51F093DFCB0F8F6FC10CB34" box="[822,903,1841,1868]" captionStart="FIG" captionStartId="6.[132,143,1916,1934]" captionTargetId="figure-32@6.[698,1267,769,1325]" captionTargetPageId="6" captionText="FIG. 1. — Generalized anatomy of living lampreys: A, schematic sagittal section through head and pharyngeal region; the vessels, esophagus, respiratory tube, and parts of the heart are shown with portions cut away, rather than in sagittal section; redrawn after De Iuliis &amp; Pulerà 2011, with the structures of the nasohypophysial complex labelled after Janvier 1974; B, the cranial skeleton of an adult lamprey, redrawn after Hardisty &amp; Potter 1981; C, arrangement pattern of the cranial nerves, redrawn after Marinelli &amp; Strenger 1954; D, oral disc of an adult lamprey showing the keratinous teeth and other associated structures. The dotted lines delineate the various fields. Redrawn after Renaud 2011." figureDoi="http://doi.org/10.5281/zenodo.5767846" httpUri="https://zenodo.org/record/5767846/files/figure.png" pageId="4" pageNumber="1295">Fig. 1C</figureCitation>
) (
<bibRefCitation id="EFA04B56F51F093DFC26F8F6FB56CB34" author="MARINELLI W. &amp; STRENGER A." box="[928,1217,1841,1868]" pageId="4" pageNumber="1295" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
: figs 51, 52).
</paragraph>
<paragraph id="8B8E36A7F51F093DFCABF8B6FC1DCBF3" blockId="4.[813,906,1905,1931]" box="[813,906,1905,1931]" pageId="4" pageNumber="1295">
<heading id="D0C681CBF51F093DFCABF8B6FC1DCBF3" box="[813,906,1905,1931]" fontSize="11" level="2" pageId="4" pageNumber="1295" reason="8">
<emphasis id="B945EAB5F51F093DFCABF8B6FC1DCBF3" box="[813,906,1905,1931]" italics="true" pageId="4" pageNumber="1295">Oral disc</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F51F093DFCABF856FA27CB93" blockId="4.[811,1456,1937,2027]" pageId="4" pageNumber="1295">
The oral disc and other associated structures are detected based on the pattern in living lamprey (
<figureCitation id="130A2A22F51F093DFB0EF876FB4CCBB4" box="[1160,1243,1969,1996]" captionStart="FIG" captionStartId="6.[132,143,1916,1934]" captionTargetId="figure-32@6.[698,1267,769,1325]" captionTargetPageId="6" captionText="FIG. 1. — Generalized anatomy of living lampreys: A, schematic sagittal section through head and pharyngeal region; the vessels, esophagus, respiratory tube, and parts of the heart are shown with portions cut away, rather than in sagittal section; redrawn after De Iuliis &amp; Pulerà 2011, with the structures of the nasohypophysial complex labelled after Janvier 1974; B, the cranial skeleton of an adult lamprey, redrawn after Hardisty &amp; Potter 1981; C, arrangement pattern of the cranial nerves, redrawn after Marinelli &amp; Strenger 1954; D, oral disc of an adult lamprey showing the keratinous teeth and other associated structures. The dotted lines delineate the various fields. Redrawn after Renaud 2011." figureDoi="http://doi.org/10.5281/zenodo.5767846" httpUri="https://zenodo.org/record/5767846/files/figure.png" pageId="4" pageNumber="1295">Fig. 1D</figureCitation>
). In larger individuals, the oral disc is well developed, with the anterior fieldwider
</paragraph>
<paragraph id="8B8E36A7F51E093CFF02FF10FDB0CE09" blockId="5.[130,777,215,911]" pageId="5" pageNumber="1296">
than the lateral and posterior ones. In IVPP
<accessionNumber id="9462AB44F51E093CFDDDFF1FFD2ACC8A" box="[603,701,215,242]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="5" pageNumber="1296" type="EnaNcbi">V 15449</accessionNumber>
, where the oral disc is best preserved, the oral disc occupies 6.64% of the total body length. In the same specimen, the impressions of a dozen of oral fimbriae (right side) are preserved in the perimeter of the oral disc (
<figureCitation id="130A2A22F51E093CFE55FE90FDDACD09" box="[467,589,343,369]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Fig. 3C, D</figureCitation>
). They are small, rod-like, and so closely arranged that they form together a comb-like pattern. This morphology is reminiscent of the oral fimbriae in living lampreys (
<bibRefCitation id="EFA04B56F51E093CFE47FE71FDC0CDA9" author="RENAUD C. B." box="[449,599,438,465]" pageId="5" pageNumber="1296" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
) and the ridges along the periphery of the oral disc of fossil lamprey
<taxonomicName id="4C314D24F51E093CFD44FE10FD9BCE68" authority="(Miyashita et al. 2021) Based" authorityName="Based" baseAuthorityName="Miyashita" baseAuthorityYear="2021" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Priscomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="5" pageNumber="1296" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51E093CFD44FE10FF50CE68" italics="true" pageId="5" pageNumber="1296">Priscomyzon</emphasis>
(
<bibRefCitation id="EFA04B56F51E093CFF5EFE31FE2ACE68" author="MIYASHITA T. &amp; GESS R. W. &amp; TIETJEN K. &amp; COATES M. I." box="[216,445,502,528]" pageId="5" pageNumber="1296" pagination="408 - 412" refId="ref12907" refString="MIYASHITA T., GESS R. W., TIETJEN K. &amp; COATES M. I. 2021. - Non-ammocoete larvae of Palaeozoic stem lampreys. Nature 591: 408 - 412. https: // doi. org / 10.1038 / s 41586 - 021 - 03305 - 9" type="journal article" year="2021">
Miyashita
<emphasis id="B945EAB5F51E093CFECCFE30FEE9CE68" box="[330,382,502,528]" italics="true" pageId="5" pageNumber="1296">et al.</emphasis>
2021
</bibRefCitation>
) Based
</taxonomicName>
on the arrangement of these structures, and the proportion of the length with the fimbriae preserved, at least 80 oral fimbriae might be present around the oral disc in IVPP
<accessionNumber id="9462AB44F51E093CFE46FD91FDB3CE09" box="[448,548,598,625]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="5" pageNumber="1296" type="EnaNcbi">V 15449</accessionNumber>
.
</paragraph>
<paragraph id="8B8E36A7F51E093CFF1DFDB1FD7CCFF7" blockId="5.[130,777,215,911]" pageId="5" pageNumber="1296">
The oral papillae are partly preserved in IVPP
<accessionNumber id="9462AB44F51E093CFD22FDB1FC90CEE9" box="[676,775,630,657]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15027" pageId="5" pageNumber="1296" type="EnaNcbi">V 15027</accessionNumber>
and 15449 (larger individuals) (
<figureCitation id="130A2A22F51E093CFE5FFD51FD8FCEC8" box="[473,536,662,688]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Figs 3</figureCitation>
A-D; 4C). They fringe the outer rim of the oral disc. The papillae are fairly large in relative to the oral disc size and triangular in shape (possibly conical as in living lampreys when the animals were alive,
<bibRefCitation id="EFA04B56F51E093CFF00FCD2FEA6CF48" author="RENAUD C. B." box="[134,305,789,816]" pageId="5" pageNumber="1296" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011: 5</bibRefCitation>
, fig. 20). They are connected to each other at the base, so that they must have entirely surrounded the oral disc. Judging from their size and arrangement, there could be no more than 30 oral papillae in the material at hand.
</paragraph>
<paragraph id="8B8E36A7F51E093CFF02FC72FEAECFB7" blockId="5.[132,313,949,975]" box="[132,313,949,975]" pageId="5" pageNumber="1296">
<heading id="D0C681CBF51E093CFF02FC72FEAECFB7" box="[132,313,949,975]" fontSize="11" level="2" pageId="5" pageNumber="1296" reason="8">
<emphasis id="B945EAB5F51E093CFF02FC72FEAECFB7" box="[132,313,949,975]" italics="true" pageId="5" pageNumber="1296">Annular cartilage</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F51E093CFF02FC13FEF8C955" blockId="5.[130,777,980,1326]" pageId="5" pageNumber="1296">
This is the structure that supports the supraoral and infraoral laminae (
<bibRefCitation id="EFA04B56F51E093CFF61FC33FEE0C877" author="RENAUD C. B." box="[231,375,1012,1039]" pageId="5" pageNumber="1296" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
). The remains of the annular cartilage are seen in some specimens, which are demonstrated either as a horseshoe-like impression (smaller individuals) or a nearly complete circle (larger individuals) (
<figureCitation id="130A2A22F51E093CFE78FB93FDABC816" box="[510,572,1108,1134]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Figs 3</figureCitation>
A-F; 4A, C). When complete, its anterior part appears to be somehow broader than the posterior part. Interestingly, in the specimen (IVPP V 15450.3) with a horseshoe-like impression of the annular cartilage, no traces of the posterior part of the cartilage are discernable although the remainder of this cartilage (element) is very well-preserved.
</paragraph>
<paragraph id="8B8E36A7F51E093CFF02FA94FF58C915" blockId="5.[132,207,1363,1389]" box="[132,207,1363,1389]" pageId="5" pageNumber="1296">
<heading id="D0C681CBF51E093CFF02FA94FF58C915" box="[132,207,1363,1389]" fontSize="11" level="2" pageId="5" pageNumber="1296" reason="8">
<emphasis id="B945EAB5F51E093CFF02FA94FF58C915" box="[132,207,1363,1389]" italics="true" pageId="5" pageNumber="1296">“Teeth”</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F51E093CFF02FAB3FC90CB93" blockId="5.[130,777,1395,2028]" pageId="5" pageNumber="1296">
In all large adult individuals with the well-preserved impression of the oral disc and annular cartilage, some non-mineralized, presumably keratinous teeth are already in place, though being developed to a lesser extent than in extant lampreys (
<bibRefCitation id="EFA04B56F51E093CFF0BFA34FE21CA75" author="MARINELLI W. &amp; STRENGER A." box="[141,438,1522,1549]" pageId="5" pageNumber="1296" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51E093CFE40FA34FDCCCA75" author="RENAUD C. B." box="[454,603,1523,1549]" pageId="5" pageNumber="1296" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
). Although the arrangement of the keratinous teeth varies among living lampreys, e.g.,
<taxonomicName id="4C314D24F51E093CFEAEF9F4FDC4CA35" authority="Gray, 1851" authorityName="Gray" authorityYear="1851" box="[296,595,1586,1613]" class="Cephalaspidomorphi" family="Geotriidae" genus="Geotria" kingdom="Animalia" order="Petromyzontiformes" pageId="5" pageNumber="1296" phylum="Chordata" rank="species" species="australis">
<emphasis id="B945EAB5F51E093CFEAEF9F4FE45CA34" box="[296,466,1586,1613]" italics="true" pageId="5" pageNumber="1296">Geotria australis</emphasis>
Gray, 1851
</taxonomicName>
has few teeth in the posterior field of the oral disc,
<taxonomicName id="4C314D24F51E093CFE7AF994FE84CAF5" authority="(Linnaeus, 1758)" authorityName="" baseAuthorityName="Linnaeus" baseAuthorityYear="1758" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Lampetra" kingdom="Animalia" order="Petromyzontiformes" pageId="5" pageNumber="1296" phylum="Chordata" rank="species" species="fluviatilis">
<emphasis id="B945EAB5F51E093CFE7AF994FD5FCA14" box="[508,712,1618,1644]" italics="true" pageId="5" pageNumber="1296">Lampetra fluviatilis</emphasis>
(Linnaeus, 1758)
</taxonomicName>
lacks anterior and posterior circumoral teeth (
<bibRefCitation id="EFA04B56F51E093CFF0BF954FE14CAD4" author="POTTER I. C. &amp; HILLIARD R. W." box="[141,387,1682,1709]" pageId="5" pageNumber="1296" pagination="713 - 737" refId="ref13156" refString="POTTER I. C. &amp; HILLIARD R. W. 1987. - A proposal for the functional and phylogenetic significance of differences in the dentition of lampreys (Agnatha: Petromyzontiformes). Journal of Zoology 212: 713 - 737. https: // doi. org / 10.1111 / j. 1469 - 7998.1987. tb 05966. x" type="journal article" year="1987">Potter &amp; Hilliard 1987</bibRefCitation>
), as a whole they all have more teeth on the oral disc than
<taxonomicName id="4C314D24F51E093CFEE4F974FE4DCAB4" authorityName="Chang, Zhang &amp; Miao" authorityYear="2006" box="[354,474,1715,1740]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="5" pageNumber="1296" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51E093CFEE4F974FE4DCAB4" box="[354,474,1715,1740]" italics="true" pageId="5" pageNumber="1296">Mesomyzon</emphasis>
</taxonomicName>
. In
<taxonomicName id="4C314D24F51E093CFD82F974FDEBCAB4" authorityName="Chang, Zhang &amp; Miao" authorityYear="2006" box="[516,636,1715,1740]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="5" pageNumber="1296" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51E093CFD82F974FDEBCAB4" box="[516,636,1715,1740]" italics="true" pageId="5" pageNumber="1296">Mesomyzon</emphasis>
</taxonomicName>
, there are no teeth preserved on the anterior, lateral and posterior fields (see
<bibRefCitation id="EFA04B56F51E093CFF30F935FE3DCB74" author="HUBBS C. L. &amp; POTTER I. C." box="[182,426,1778,1804]" pageId="5" pageNumber="1296" pagination="1 - 65" refId="ref11905" refString="HUBBS C. L. &amp; POTTER I. C. 1971. - Distribution, phylogeny and taxonomy, in HARDISTY M. W. &amp; POTTER I. C. (eds), The Biology of Lampreys. Volume 1. Academic Press, London: 1 - 65." type="book chapter" year="1971">Hubbs &amp; Potter 1971</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51E093CFE3CF935FDD8CB74" author="RENAUD C. B." box="[442,591,1778,1804]" pageId="5" pageNumber="1296" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
and
<figureCitation id="130A2A22F51E093CFD0DF935FD48CB74" box="[651,735,1778,1804]" captionStart="FIG" captionStartId="6.[132,143,1916,1934]" captionTargetId="figure-32@6.[698,1267,769,1325]" captionTargetPageId="6" captionText="FIG. 1. — Generalized anatomy of living lampreys: A, schematic sagittal section through head and pharyngeal region; the vessels, esophagus, respiratory tube, and parts of the heart are shown with portions cut away, rather than in sagittal section; redrawn after De Iuliis &amp; Pulerà 2011, with the structures of the nasohypophysial complex labelled after Janvier 1974; B, the cranial skeleton of an adult lamprey, redrawn after Hardisty &amp; Potter 1981; C, arrangement pattern of the cranial nerves, redrawn after Marinelli &amp; Strenger 1954; D, oral disc of an adult lamprey showing the keratinous teeth and other associated structures. The dotted lines delineate the various fields. Redrawn after Renaud 2011." figureDoi="http://doi.org/10.5281/zenodo.5767846" httpUri="https://zenodo.org/record/5767846/files/figure.png" pageId="5" pageNumber="1296">Fig. 1D</figureCitation>
for delineation) of the oral disc outside of the circumoral teeth. Given the good preservation of the circumoral teeth under the same taphonomic condition, teeth might be absent, or at least very weakly developed on those fields. The series of the circumoral teeth is incomplete, only the anterior and lateral rows are prominent. These triangular teeth are relatively loosely arranged and similar in size. The teeth on the
</paragraph>
<paragraph id="8B8E36A7F51E093CFCA8FF10FA8CCDC9" blockId="5.[812,1456,215,433]" pageId="5" pageNumber="1296">
supraoral lamina are strong and bicuspid (
<figureCitation id="130A2A22F51E093CFB7FFF10FA3DCC8A" box="[1273,1450,215,242]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Figs 3A, B, E, F</figureCitation>
;
<figureCitation id="130A2A22F51E093CFCA8FF30FCE7CD69" box="[814,880,247,273]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="5" pageNumber="1296">4A, C</figureCitation>
). Those on the infraoral lamina are occasionally seen, and are also roughly triangular in shape (
<figureCitation id="130A2A22F51E093CFB64FED0FAC4CD4A" box="[1250,1363,279,306]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Figs 3A, B</figureCitation>
;
<figureCitation id="130A2A22F51E093CFAD8FED0FA35CD49" box="[1374,1442,279,305]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="5" pageNumber="1296">4A, C</figureCitation>
). Although their detailed structure of the transversal and longitudinal lingual laminae can be recognized, some dark matter preserved roughly at the anterior end of the piston cartilage might suggest their presence (
<figureCitation id="130A2A22F51E093CFBEBFE51FB3ACDC9" box="[1133,1197,406,433]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Figs 3</figureCitation>
B-D; 4A).
</paragraph>
<paragraph id="8B8E36A7F51E093CFCABFE11FBA6CD88" blockId="5.[813,1073,470,497]" box="[813,1073,470,497]" pageId="5" pageNumber="1296">
<heading id="D0C681CBF51E093CFCABFE11FBA6CD88" box="[813,1073,470,497]" fontSize="11" level="2" pageId="5" pageNumber="1296" reason="8">
<emphasis id="B945EAB5F51E093CFCABFE11FBA6CD88" box="[813,1073,470,497]" italics="true" pageId="5" pageNumber="1296">Lingual (piston) cartilage</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F51E093CFCABFE31FB0CCF37" blockId="5.[811,1456,502,848]" pageId="5" pageNumber="1296">
The piston cartilage is usually preserved as a slender longitudinal band extending along the ventral part of the pharynx from the mouth and posteriorly towards the branchial region (
<figureCitation id="130A2A22F51E093CFCB3FD91FCE7CE08" box="[821,880,598,624]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Fig. 3</figureCitation>
B-D). In IVPP
<accessionNumber id="9462AB44F51E093CFB88FD91FBF0CE09" box="[1038,1127,598,625]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15035" pageId="5" pageNumber="1296" type="EnaNcbi">V 15035</accessionNumber>
A (
<figureCitation id="130A2A22F51E093CFB0EFD91FB4FCE08" box="[1160,1240,598,624]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Figs 3B</figureCitation>
;
<figureCitation id="130A2A22F51E093CFB67FD91FA93CE08" box="[1249,1284,598,624]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="5" pageNumber="1296">4A</figureCitation>
), IVPP
<accessionNumber id="9462AB44F51E093CFAD5FD91FA27CE09" box="[1363,1456,598,625]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="5" pageNumber="1296" type="EnaNcbi">V 15449</accessionNumber>
(
<figureCitation id="130A2A22F51E093CFCB3FDB1FC3FCEE8" box="[821,936,630,656]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Fig. 3C, D</figureCitation>
), the anterior end of the piston cartilage, or apical cartilage, can be roughly recognized. It is continuous with the remaining part of this cartilage. This part is obviously darker in color than other part of the cartilage, possibly suggesting the fairly thick and complex structure (e.g., the apicalis cartilage) as in living lampreys (
<bibRefCitation id="EFA04B56F51E093CFB03FCD2FA3FCF48" author="MARINELLI W. &amp; STRENGER A." box="[1157,1448,789,816]" pageId="5" pageNumber="1296" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
: figs 19-21;
<bibRefCitation id="EFA04B56F51E093CFC21FCF2FBA7CF37" author="JANVIER P." box="[935,1072,821,847]" pageId="5" pageNumber="1296" pagination="131 - 188" refId="ref12070" refString="JANVIER P. 1993. - Patterns of diversity in the skull of jawless fishes, in HANKEN J. &amp; HALL B. K. (eds), The Skull. University of Chicago Press, Chicago: 131 - 188." type="book chapter" year="1993">
<date id="FF8F1067F51E093CFC21FCF2FBA7CF37" box="[935,1072,821,847]" pageId="5" pageNumber="1296" value="1993-01">Janvier 1993</date>
</bibRefCitation>
: fig. 4.4).
</paragraph>
<paragraph id="8B8E36A7F51E093CFCABFCB2FC2FCFF7" blockId="5.[813,952,885,911]" box="[813,952,885,911]" pageId="5" pageNumber="1296">
<heading id="D0C681CBF51E093CFCABFCB2FC2FCFF7" box="[813,952,885,911]" fontSize="11" level="2" pageId="5" pageNumber="1296" reason="8">
<emphasis id="B945EAB5F51E093CFCABFCB2FC2FCFF7" box="[813,952,885,911]" italics="true" pageId="5" pageNumber="1296">Velar skeleton</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F51E093CFCABFC52FAFDC8D6" blockId="5.[811,1457,917,1198]" pageId="5" pageNumber="1296">
Immediately in front of the branchial apparatus, there is a prominent dark impression with an irregular profile (
<figureCitation id="130A2A22F51E093CFADCFC72FA3DCFB7" box="[1370,1450,949,975]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Figs 3B</figureCitation>
;
<figureCitation id="130A2A22F51E093CFCABFC12FCD9CF97" box="[813,846,981,1007]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="5" pageNumber="1296">4A</figureCitation>
) which points to velar skeleton on the basis of the comparison to its homologue in extant lampreys (in
<figureCitation id="130A2A22F51E093CFAB7FC33FA17C877" box="[1329,1408,1012,1039]" captionStart="FIG" captionStartId="6.[132,143,1916,1934]" captionTargetId="figure-32@6.[698,1267,769,1325]" captionTargetPageId="6" captionText="FIG. 1. — Generalized anatomy of living lampreys: A, schematic sagittal section through head and pharyngeal region; the vessels, esophagus, respiratory tube, and parts of the heart are shown with portions cut away, rather than in sagittal section; redrawn after De Iuliis &amp; Pulerà 2011, with the structures of the nasohypophysial complex labelled after Janvier 1974; B, the cranial skeleton of an adult lamprey, redrawn after Hardisty &amp; Potter 1981; C, arrangement pattern of the cranial nerves, redrawn after Marinelli &amp; Strenger 1954; D, oral disc of an adult lamprey showing the keratinous teeth and other associated structures. The dotted lines delineate the various fields. Redrawn after Renaud 2011." figureDoi="http://doi.org/10.5281/zenodo.5767846" httpUri="https://zenodo.org/record/5767846/files/figure.png" pageId="5" pageNumber="1296">Fig. 1A</figureCitation>
and
<bibRefCitation id="EFA04B56F51E093CFCAAFBD3FBD5C857" author="MARINELLI W. &amp; STRENGER A." box="[812,1090,1044,1071]" pageId="5" pageNumber="1296" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
: figs 64, 65;
<bibRefCitation id="EFA04B56F51E093CFB42FBD3FADEC856" author="JANVIER P." box="[1220,1353,1044,1070]" pageId="5" pageNumber="1296" pagination="131 - 188" refId="ref12070" refString="JANVIER P. 1993. - Patterns of diversity in the skull of jawless fishes, in HANKEN J. &amp; HALL B. K. (eds), The Skull. University of Chicago Press, Chicago: 131 - 188." type="book chapter" year="1993">
<date id="FF8F1067F51E093CFB42FBD3FADEC856" box="[1220,1353,1044,1070]" pageId="5" pageNumber="1296" value="1993-01">Janvier 1993</date>
</bibRefCitation>
: fig. 4.4). More dorsally, there is a band-like impression extending anterodorsally toward the cranium, which is likely the imprinted styliform cartilage.This cartilage is linked to the velar skeleton by some muscles in modern lampreys (
<bibRefCitation id="EFA04B56F51E093CFB57FB53FACDC8D6" author="JANVIER P." box="[1233,1370,1172,1198]" pageId="5" pageNumber="1296" pagination="131 - 188" refId="ref12070" refString="JANVIER P. 1993. - Patterns of diversity in the skull of jawless fishes, in HANKEN J. &amp; HALL B. K. (eds), The Skull. University of Chicago Press, Chicago: 131 - 188." type="book chapter" year="1993">
<date id="FF8F1067F51E093CFB57FB53FACDC8D6" box="[1233,1370,1172,1198]" pageId="5" pageNumber="1296" value="1993-01">Janvier 1993</date>
</bibRefCitation>
).
</paragraph>
<paragraph id="8B8E36A7F51E093CFCABFB13FC6AC895" blockId="5.[813,1021,1236,1262]" box="[813,1021,1236,1262]" pageId="5" pageNumber="1296">
<heading id="D0C681CBF51E093CFCABFB13FC6AC895" box="[813,1021,1236,1262]" fontSize="11" level="2" pageId="5" pageNumber="1296" reason="8">
<emphasis id="B945EAB5F51E093CFCABFB13FC6AC895" box="[813,1021,1236,1262]" italics="true" pageId="5" pageNumber="1296">Branchial apparatus</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F51E093CFCABFB34FA38CB93" blockId="5.[811,1457,1267,2027]" pageId="5" pageNumber="1296">
The distance between the eye and the branchial apparatus roughly equals the interval of four branchial openings. Seven gill pouches are seen, slightly slanting posteriorly, and of which the foremost one is triangular and much smaller than the remaining ones (
<figureCitation id="130A2A22F51E093CFB96FAB4FBFFC9F5" box="[1040,1128,1395,1421]" captionStart="FIG" captionStartId="8.[132,143,1381,1399]" captionTargetBox="[132,1455,215,1322]" captionTargetId="figure-353@8.[132,1455,214,1339]" captionTargetPageId="8" captionText="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="5" pageNumber="1296">Figs 2C</figureCitation>
;
<figureCitation id="130A2A22F51E093CFBF3FAB4FB16C9F5" box="[1141,1153,1395,1421]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">3</figureCitation>
A-D). The branchial basket is partially preserved in IVPP
<accessionNumber id="9462AB44F51E093CFBF5FA53FB47C9D6" box="[1139,1232,1427,1454]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15027" pageId="5" pageNumber="1296" type="EnaNcbi">V 15027</accessionNumber>
A and 15449, where the impressions of the ventral part of branchial basket is well exposed. In the anteriormost part, some relics of the extra hyal arch can be detected (
<figureCitation id="130A2A22F51E093CFBCBFA34FB51CA75" box="[1101,1222,1523,1549]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Figs 3C, D</figureCitation>
;
<figureCitation id="130A2A22F51E093CFB54FA34FA8FCA75" box="[1234,1304,1523,1549]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="5" pageNumber="1296">4D, E</figureCitation>
). More posteriorly, each of the branchial units shows a reversed Y-shaped profile in lateral view, which is connected ventrally with the longitudinal hypobranchial bar (
<figureCitation id="130A2A22F51E093CFB31F995FAC7CA15" box="[1207,1360,1618,1645]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="5" pageNumber="1296">Figs 3A, C, D</figureCitation>
;
<figureCitation id="130A2A22F51E093CFADBF995FA34CA15" box="[1373,1443,1618,1645]" captionStart="FIG" captionStartId="12.[132,143,1917,1935]" captionTargetBox="[136,1451,217,1872]" captionTargetId="figure-24@12.[136,1451,219,1873]" captionTargetPageId="12" captionText="FIG. 4. — Close-up of some anatomical structures of Mesomyzon Chang, Zhang &amp; Miao, 2006: A, head of IVPP V 15035A; B, naso-hypophysial complex and adjacent structures of IVPP V 15449; C, oral disc and associated structures of IVPP V 15027A; D, details of gills and branchial skeleton of IVPP V 15449; E, details of the branchial apparatus of IVPP V 15027A; F, imprints of the brain and some cranial nerves of IVPP V 15450.3. Abbreviations: alc, anterior lateral cartilage; nhd, naso-hypophysial duct; fr, presumed position of fossa rhomboidea; g1, gill filaments of the first gill; nsc2, ventral spino-occipital radix nerve. See Figures 1 and 2 for other abbreviations. Scale bars: 5 mm." figureDoi="http://doi.org/10.5281/zenodo.5764685" httpUri="https://zenodo.org/record/5764685/files/figure.png" pageId="5" pageNumber="1296">4D, E</figureCitation>
). Based on the position relative to the external gill openings, this fork must be positioned below the hypotrematic bar, by comparison to the arrangement of gill basket in living lampreys (
<figureCitation id="130A2A22F51E093CFC1AF915FC7BCA94" box="[924,1004,1746,1772]" captionStart="FIG" captionStartId="6.[132,143,1916,1934]" captionTargetId="figure-32@6.[698,1267,769,1325]" captionTargetPageId="6" captionText="FIG. 1. — Generalized anatomy of living lampreys: A, schematic sagittal section through head and pharyngeal region; the vessels, esophagus, respiratory tube, and parts of the heart are shown with portions cut away, rather than in sagittal section; redrawn after De Iuliis &amp; Pulerà 2011, with the structures of the nasohypophysial complex labelled after Janvier 1974; B, the cranial skeleton of an adult lamprey, redrawn after Hardisty &amp; Potter 1981; C, arrangement pattern of the cranial nerves, redrawn after Marinelli &amp; Strenger 1954; D, oral disc of an adult lamprey showing the keratinous teeth and other associated structures. The dotted lines delineate the various fields. Redrawn after Renaud 2011." figureDoi="http://doi.org/10.5281/zenodo.5767846" httpUri="https://zenodo.org/record/5767846/files/figure.png" pageId="5" pageNumber="1296">Fig. 1B</figureCitation>
) (
<bibRefCitation id="EFA04B56F51E093CFB82F915FAB2CA95" author="MARINELLI W. &amp; STRENGER A." box="[1028,1317,1746,1773]" pageId="5" pageNumber="1296" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
). This is different from the living lampreys in lacking the slanting rods above the junction of this bar and each extrabranchial arch as the attachment area of some external branchial constrictor muscles (
<bibRefCitation id="EFA04B56F51E093CFC16F896FB25CB14" author="MARINELLI W. &amp; STRENGER A." box="[912,1202,1873,1900]" pageId="5" pageNumber="1296" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
: figs 13, 14). Although we cannot say with certainty that this suggests difference in the configuration of the branchial muscles, the available information indeed reflects some structural variations of the gill-supporting architecture between
<taxonomicName id="4C314D24F51E093CFA84F815FAE9CB93" authorityName="Chang, Zhang &amp; Miao" authorityYear="2006" box="[1282,1406,2002,2027]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="5" pageNumber="1296" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51E093CFA84F815FAE9CB93" box="[1282,1406,2002,2027]" italics="true" pageId="5" pageNumber="1296">Mesomyzon</emphasis>
</taxonomicName>
and
</paragraph>
<paragraph id="8B8E36A7F51D093FFE75FF2EFD15CD1F" blockId="6.[225,852,233,377]" pageId="6" pageNumber="1297">olfactory pineal organ naso-hypophysial organ notochord atrium hypophysial pouch brain</paragraph>
<caption id="DF4E662FF51D093FFF02F8BBFD10CB91" ID-DOI="http://doi.org/10.5281/zenodo.5767846" ID-Zenodo-Dep="5767846" httpUri="https://zenodo.org/record/5767846/files/figure.png" pageId="6" pageNumber="1297" startId="6.[132,143,1916,1934]" targetBox="[132,1450,218,1864]" targetPageId="6">
<paragraph id="8B8E36A7F51D093FFF02F8BBFD10CB91" blockId="6.[132,1457,1916,2025]" pageId="6" pageNumber="1297">
FIG. 1. — Generalized anatomy of living lampreys:
<emphasis id="B945EAB5F51D093FFDA1F8BBFDA3CBF6" bold="true" box="[551,564,1916,1934]" pageId="6" pageNumber="1297">A</emphasis>
, schematic sagittal section through head and pharyngeal region; the vessels, esophagus, respiratory tube, and parts of the heart are shown with portions cut away, rather than in sagittal section; redrawn after
<bibRefCitation id="EFA04B56F51D093FFC5BF855FB0BCBDC" author="DE IULIIS G. &amp; PULERA D." box="[989,1180,1938,1956]" pageId="6" pageNumber="1297" refId="ref11693" refString="DE IULIIS G. &amp; PULERA D. 2011. - The Dissection of Vertebrates: A Laboratory Manual. Academic Press. https: // doi. org / 10.1016 / C 2009 - 0 - 00124 - X" type="book" year="2011">De Iuliis &amp; Pulerà 2011</bibRefCitation>
, with the structures of the nasohypophysial complex labelled after
<bibRefCitation id="EFA04B56F51D093FFE2FF86EFD84CBC3" author="JANVIER P." box="[425,531,1961,1979]" pageId="6" pageNumber="1297" pagination="193 - 200" refId="ref12015" refString="JANVIER P. 1974. - The structure of the naso-hypophysial complex and the mouth in fossil and extant cyclostomes, with remarks on amphiaspiforms. Zoologica Scripta, Stockholm 3: 193 - 200. https: // doi. org / 10.1111 / j. 1463 - 6409.1974. tb 00816. x" type="journal article" year="1974">Janvier 1974</bibRefCitation>
;
<emphasis id="B945EAB5F51D093FFD9BF86EFDBDCBC3" bold="true" box="[541,554,1961,1979]" pageId="6" pageNumber="1297">B</emphasis>
, the cranial skeleton of an adult lamprey, redrawn after
<bibRefCitation id="EFA04B56F51D093FFC72F86EFB27CBC3" author="HARDISTY M. W. &amp; POTTER I. C." box="[1012,1200,1961,1979]" pageId="6" pageNumber="1297" pagination="118 - 124" refId="ref11958" refString="HARDISTY M. W. &amp; POTTER I. C. 1981. - The skeleton, in The biology of lampreys. in HARDISTY M. W. &amp; POTTER I. C. (eds), The Biology of Lampreys. Volume 3. Academic Press, New York: 118 - 124." type="book chapter" year="1981">Hardisty &amp; Potter 1981</bibRefCitation>
;
<emphasis id="B945EAB5F51D093FFB3FF86EFB50CBC3" bold="true" box="[1209,1223,1961,1979]" pageId="6" pageNumber="1297">C</emphasis>
, arrangement pattern of the cranial nerves, redrawn after
<bibRefCitation id="EFA04B56F51D093FFEF5F807FDD4CBAA" author="MARINELLI W. &amp; STRENGER A." box="[371,579,1984,2002]" pageId="6" pageNumber="1297" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
;
<emphasis id="B945EAB5F51D093FFDCBF807FDCCCBAA" bold="true" box="[589,603,1984,2002]" pageId="6" pageNumber="1297">D</emphasis>
, oral disc of an adult lamprey showing the keratinous teeth and other associated structures. The dotted lines delineate the various fields. Redrawn after
<bibRefCitation id="EFA04B56F51D093FFD94F810FD15CB91" author="RENAUD C. B." box="[530,642,2007,2025]" pageId="6" pageNumber="1297" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
.
</paragraph>
</caption>
<caption id="DF4E662FF51C093EFF02FF1CFD8FCD30" ID-Table-UUID="DF4E662FF51C093EFF02FF1CFD8FCD30" httpUri="http://table.plazi.org/id/DF4E662FF51C093EFF02FF1CFD8FCD30" pageId="7" pageNumber="1298" startId="7.[132,143,219,237]" targetBox="[134,1429,389,517]" targetIsTable="true" targetPageId="7">
<paragraph id="8B8E36A7F51C093EFF02FF1CFD8FCD30" blockId="7.[132,1457,219,331]" pageId="7" pageNumber="1298">
TABLE 1. — Meristic measurements of
<taxonomicName id="4C314D24F51C093EFE39FF1CFCCBCC95" authority="Chang, Zhang &amp; Miao, 2006" authorityName="Chang, Zhang &amp; Miao" authorityYear="2006" box="[447,860,219,237]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="species" species="mengae">
<emphasis id="B945EAB5F51C093EFE39FF1CFDFBCC95" box="[447,620,219,237]" italics="true" pageId="7" pageNumber="1298">Mesomyzon mengae</emphasis>
<bibRefCitation id="EFA04B56F51C093EFDF6FF1CFCCBCC95" author="CHANG M. - M. &amp; ZHANG J. Y. &amp; MIAO D. S." box="[624,860,219,237]" pageId="7" pageNumber="1298" pagination="972 - 974" refId="ref11511" refString="CHANG M. - M., ZHANG J. Y. &amp; MIAO D. S. 2006. - A lamprey from the Cretaceous Jehol biota of China. Nature 441: 972 - 974. https: // doi. org / 10.1038 / nature 04730" type="journal article" year="2006">Chang, Zhang &amp; Miao, 2006</bibRefCitation>
</taxonomicName>
. Abbreviations and interpretations:
<emphasis id="B945EAB5F51C093EFB06FF1CFB1CCC95" bold="true" box="[1152,1163,219,237]" pageId="7" pageNumber="1298">a</emphasis>
, cloacal slit length;
<emphasis id="B945EAB5F51C093EFAA9FF1CFAD8CC95" bold="true" box="[1327,1359,219,237]" pageId="7" pageNumber="1298">a-C</emphasis>
, tail length;
<emphasis id="B945EAB5F51C093EFF02FF35FF18CD7C" bold="true" box="[132,143,242,260]" pageId="7" pageNumber="1298">d</emphasis>
, oral disc length;
<emphasis id="B945EAB5F51C093EFE99FF35FED6CD7C" bold="true" box="[287,321,242,260]" pageId="7" pageNumber="1298">d-O</emphasis>
, preorbital length (from anteriormost internal edge of oral disc to anterior edge of eye);
<emphasis id="B945EAB5F51C093EFB82FF35FBB9CD7C" bold="true" box="[1028,1070,242,260]" pageId="7" pageNumber="1298">d-B1</emphasis>
, prebranchial length or head length;
<emphasis id="B945EAB5F51C093EFADFFF35FAE0CD7C" bold="true" box="[1369,1399,242,260]" pageId="7" pageNumber="1298">d-n</emphasis>
, snout length (narial opening not well-preserved, measured between anterior edge of naso-hypophysial organ to anteriormost internal edge of oral disc);
<emphasis id="B945EAB5F51C093EFACFFECEFAEECD65" bold="true" box="[1353,1401,265,285]" pageId="7" pageNumber="1298">
B
<subScript id="17B534E2F51C093EFAD0FED7FACACD65" attach="left" box="[1366,1373,272,285]" fontSize="5" pageId="7" pageNumber="1298">1</subScript>
-B
<subScript id="17B534E2F51C093EFAF4FED7FAEECD65" attach="left" box="[1394,1401,272,285]" fontSize="5" pageId="7" pageNumber="1298">2</subScript>
</emphasis>
, interbranchial opening length;
<emphasis id="B945EAB5F51C093EFEDCFED8FE1DCD4C" bold="true" box="[346,394,287,308]" pageId="7" pageNumber="1298">
B
<subScript id="17B534E2F51C093EFEE1FEE0FEF9CD4C" attach="left" box="[359,366,295,308]" fontSize="5" pageId="7" pageNumber="1298">1</subScript>
-B
<subScript id="17B534E2F51C093EFE05FEE0FE1DCD4C" attach="left" box="[387,394,295,308]" fontSize="5" pageId="7" pageNumber="1298">7</subScript>
</emphasis>
, branchial length;
<emphasis id="B945EAB5F51C093EFDA4FED8FDDECD49" bold="true" box="[546,585,287,308]" pageId="7" pageNumber="1298">
B
<subScript id="17B534E2F51C093EFDA9FEE0FDA1CD4C" attach="left" box="[559,566,295,308]" fontSize="5" pageId="7" pageNumber="1298">7</subScript>
-a
</emphasis>
, trunk length;
<emphasis id="B945EAB5F51C093EFD38FED8FD40CD49" bold="true" box="[702,727,287,305]" pageId="7" pageNumber="1298">Hh</emphasis>
, head height (measured at the level of posterior edge of eye);
<emphasis id="B945EAB5F51C093EFB57FED8FB40CD49" bold="true" box="[1233,1239,287,305]" pageId="7" pageNumber="1298">I</emphasis>
, interocular length;
<emphasis id="B945EAB5F51C093EFAFCFED8FA1ECD49" bold="true" box="[1402,1417,287,305]" pageId="7" pageNumber="1298">O</emphasis>
, eye length;
<emphasis id="B945EAB5F51C093EFF44FEF1FF7BCD33" bold="true" box="[194,236,310,331]" pageId="7" pageNumber="1298">
O-B
<subScript id="17B534E2F51C093EFF63FEF9FF7BCD33" attach="left" box="[229,236,318,331]" fontSize="5" pageId="7" pageNumber="1298">1</subScript>
</emphasis>
, postocular length;
<emphasis id="B945EAB5F51C093EFE15FEF1FE3ECD30" bold="true" box="[403,425,310,328]" pageId="7" pageNumber="1298">TL</emphasis>
, total length.
</paragraph>
</caption>
<paragraph id="8B8E36A7F51C093EFEA7FE42FA02CE7D" pageId="7" pageNumber="1298">
<table id="F931C407F51CF6C6FF00FE42FA02CE7D" box="[134,1429,389,517]" gridcols="14" gridrows="5" pageId="7" pageNumber="1298">
<tr id="350134E5F51CF6C6FF00FE42FA02CDE1" box="[134,1429,389,409]" gridrow="0" pageId="7" pageNumber="1298" rowspan-0="1">
<th id="76D05D99F51CF6C6FE97FE42FEDBCDE1" box="[273,332,389,409]" gridcol="1" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFEA7FE42FEACCDE1" bold="true" box="[289,315,389,409]" pageId="7" pageNumber="1298">TL</emphasis>
</th>
<th id="76D05D99F51CF6C6FEFAFE42FE3BCDE1" box="[380,428,389,409]" gridcol="2" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFEFAFE42FE3BCDE1" bold="true" box="[380,428,389,409]" pageId="7" pageNumber="1298">B7-a</emphasis>
</th>
<th id="76D05D99F51CF6C6FE59FE42FD93CDE1" box="[479,516,389,409]" gridcol="3" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFE59FE42FD93CDE1" bold="true" box="[479,516,389,409]" pageId="7" pageNumber="1298">a-C</emphasis>
</th>
<th id="76D05D99F51CF6C6FDBCFE42FDF3CDE1" box="[570,612,389,409]" gridcol="4" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFDB8FE42FDF7CDE1" bold="true" box="[574,608,389,409]" pageId="7" pageNumber="1298">d-n</emphasis>
</th>
<th id="76D05D99F51CF6C6FD1BFE42FD2CCDE1" box="[669,699,389,409]" gridcol="5" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFD22FE42FD22CDE1" bold="true" box="[676,693,389,409]" pageId="7" pageNumber="1298">O</emphasis>
</th>
<th id="76D05D99F51CF6C6FD69FE42FCB3CDE1" box="[751,804,389,409]" gridcol="6" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFD69FE42FCB3CDE1" bold="true" box="[751,804,389,409]" pageId="7" pageNumber="1298">O-B1</emphasis>
</th>
<th id="76D05D99F51CF6C6FCCEFE42FC11CDE1" box="[840,902,389,409]" gridcol="7" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFCCEFE42FC11CDE1" bold="true" box="[840,902,389,409]" pageId="7" pageNumber="1298">B1-B2</emphasis>
</th>
<th id="76D05D99F51CF6C6FC29FE42FC4ECDE1" box="[943,985,389,409]" gridcol="8" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFC30FE42FC45CDE1" bold="true" box="[950,978,389,409]" pageId="7" pageNumber="1298">Hh</emphasis>
</th>
<th id="76D05D99F51CF6C6FB95FE42FBA6CDE1" box="[1043,1073,389,409]" gridcol="9" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFB9DFE42FBBFCDE1" bold="true" box="[1051,1064,389,409]" pageId="7" pageNumber="1298">d</emphasis>
</th>
<th id="76D05D99F51CF6C6FBECFE42FB03CDE1" box="[1130,1172,389,409]" gridcol="10" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFBEAFE42FB05CDE1" bold="true" box="[1132,1170,389,409]" pageId="7" pageNumber="1298">d-O</emphasis>
</th>
<th id="76D05D99F51CF6C6FB42FE42FB62CDE1" box="[1220,1269,389,409]" gridcol="11" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFB42FE42FB62CDE1" bold="true" box="[1220,1269,389,409]" pageId="7" pageNumber="1298">d-B1</emphasis>
</th>
<th id="76D05D99F51CF6C6FA9BFE42FACBCDE1" box="[1309,1372,389,409]" gridcol="12" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFA9BFE42FACBCDE1" bold="true" box="[1309,1372,389,409]" pageId="7" pageNumber="1298">B1-B7</emphasis>
</th>
<th id="76D05D99F51CF6C6FA0EFE42FA02CDE1" box="[1416,1429,389,409]" gridcol="13" gridrow="0" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFA0EFE42FA03CDE1" bold="true" box="[1416,1428,389,409]" pageId="7" pageNumber="1298">a</emphasis>
</th>
</tr>
<tr id="350134E5F51CF6C6FF00FE6EFA02CDC5" box="[134,1429,425,445]" gridrow="1" pageId="7" pageNumber="1298">
<th id="76D05D99F51CF6C6FF00FE6EFF4BCDC5" box="[134,220,425,445]" gridcol="0" gridrow="1" pageId="7" pageNumber="1298">
<accessionNumber id="9462AB44F51C093EFF00FE6EFF59CDC5" box="[134,206,425,445]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V14981" pageId="7" pageNumber="1298" type="EnaNcbi">V14981</accessionNumber>
</th>
<td id="76D05D99F51CF6C6FE97FE6EFEDBCDC5" box="[273,332,425,445]" gridcol="1" gridrow="1" pageId="7" pageNumber="1298">
<emphasis id="B945EAB5F51C093EFE97FE6EFEB4CDC5" box="[273,291,425,445]" italics="true" pageId="7" pageNumber="1298">c.</emphasis>
150
</td>
<td id="76D05D99F51CF6C6FEFAFE6EFE3BCDC5" box="[380,428,425,445]" gridcol="2" gridrow="1" pageId="7" pageNumber="1298">74</td>
<td id="76D05D99F51CF6C6FE59FE6EFD93CDC5" box="[479,516,425,445]" gridcol="3" gridrow="1" pageId="7" pageNumber="1298">37</td>
<td id="76D05D99F51CF6C6FDBCFE6EFDF3CDC5" box="[570,612,425,445]" gridcol="4" gridrow="1" pageId="7" pageNumber="1298">?</td>
<td id="76D05D99F51CF6C6FD1BFE6EFD2CCDC5" box="[669,699,425,445]" gridcol="5" gridrow="1" pageId="7" pageNumber="1298">?</td>
<td id="76D05D99F51CF6C6FD69FE6EFCB3CDC5" box="[751,804,425,445]" gridcol="6" gridrow="1" pageId="7" pageNumber="1298">?</td>
<td id="76D05D99F51CF6C6FCCEFE6EFC11CDC5" box="[840,902,425,445]" gridcol="7" gridrow="1" pageId="7" pageNumber="1298">2</td>
<td id="76D05D99F51CF6C6FC29FE6EFC4ECDC5" box="[943,985,425,445]" gridcol="8" gridrow="1" pageId="7" pageNumber="1298">?</td>
<td id="76D05D99F51CF6C6FB95FE6EFBA6CDC5" box="[1043,1073,425,445]" gridcol="9" gridrow="1" pageId="7" pageNumber="1298">?</td>
<td id="76D05D99F51CF6C6FBECFE6EFB03CDC5" box="[1130,1172,425,445]" gridcol="10" gridrow="1" pageId="7" pageNumber="1298">?</td>
<td id="76D05D99F51CF6C6FB42FE6EFB62CDC5" box="[1220,1269,425,445]" gridcol="11" gridrow="1" pageId="7" pageNumber="1298">20</td>
<td id="76D05D99F51CF6C6FA9BFE6EFACBCDC5" box="[1309,1372,425,445]" gridcol="12" gridrow="1" pageId="7" pageNumber="1298">13</td>
<td id="76D05D99F51CF6C6FA0EFE6EFA02CDC5" box="[1416,1429,425,445]" gridcol="13" gridrow="1" pageId="7" pageNumber="1298">2</td>
</tr>
<tr id="350134E5F51CF6C6FF00FE06FA02CDAD" box="[134,1429,449,469]" gridrow="2" pageId="7" pageNumber="1298">
<th id="76D05D99F51CF6C6FF00FE06FF4BCDAD" box="[134,220,449,469]" gridcol="0" gridrow="2" pageId="7" pageNumber="1298">
<accessionNumber id="9462AB44F51C093EFF00FE06FF5ACDAD" box="[134,205,449,469]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15448" pageId="7" pageNumber="1298" type="EnaNcbi">V15448</accessionNumber>
A
</th>
<td id="76D05D99F51CF6C6FE97FE06FEDBCDAD" box="[273,332,449,469]" gridcol="1" gridrow="2" pageId="7" pageNumber="1298">186</td>
<td id="76D05D99F51CF6C6FEFAFE06FE3BCDAD" box="[380,428,449,469]" gridcol="2" gridrow="2" pageId="7" pageNumber="1298">99</td>
<td id="76D05D99F51CF6C6FE59FE06FD93CDAD" box="[479,516,449,469]" gridcol="3" gridrow="2" pageId="7" pageNumber="1298">41</td>
<td id="76D05D99F51CF6C6FDBCFE06FDF3CDAD" box="[570,612,449,469]" gridcol="4" gridrow="2" pageId="7" pageNumber="1298">16.5</td>
<td id="76D05D99F51CF6C6FD1BFE06FD2CCDAD" box="[669,699,449,469]" gridcol="5" gridrow="2" pageId="7" pageNumber="1298">2.5</td>
<td id="76D05D99F51CF6C6FD69FE06FCB3CDAD" box="[751,804,449,469]" gridcol="6" gridrow="2" pageId="7" pageNumber="1298">8</td>
<td id="76D05D99F51CF6C6FCCEFE06FC11CDAD" box="[840,902,449,469]" gridcol="7" gridrow="2" pageId="7" pageNumber="1298">2.5</td>
<td id="76D05D99F51CF6C6FC29FE06FC4ECDAD" box="[943,985,449,469]" gridcol="8" gridrow="2" pageId="7" pageNumber="1298">12</td>
<td id="76D05D99F51CF6C6FB95FE06FBA6CDAD" box="[1043,1073,449,469]" gridcol="9" gridrow="2" pageId="7" pageNumber="1298">13</td>
<td id="76D05D99F51CF6C6FBECFE06FB03CDAD" box="[1130,1172,449,469]" gridcol="10" gridrow="2" pageId="7" pageNumber="1298">17</td>
<td id="76D05D99F51CF6C6FB42FE06FB62CDAD" box="[1220,1269,449,469]" gridcol="11" gridrow="2" pageId="7" pageNumber="1298">25.5</td>
<td id="76D05D99F51CF6C6FA9BFE06FACBCDAD" box="[1309,1372,449,469]" gridcol="12" gridrow="2" pageId="7" pageNumber="1298">18</td>
<td id="76D05D99F51CF6C6FA0EFE06FA02CDAD" box="[1416,1429,449,469]" gridcol="13" gridrow="2" pageId="7" pageNumber="1298">?</td>
</tr>
<tr id="350134E5F51CF6C6FF00FE1EFA02CD95" box="[134,1429,473,493]" gridrow="3" pageId="7" pageNumber="1298">
<th id="76D05D99F51CF6C6FF00FE1EFF4BCD95" box="[134,220,473,493]" gridcol="0" gridrow="3" pageId="7" pageNumber="1298">
<accessionNumber id="9462AB44F51C093EFF00FE1EFF59CD95" box="[134,206,473,493]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15027" pageId="7" pageNumber="1298" type="EnaNcbi">V15027</accessionNumber>
</th>
<td id="76D05D99F51CF6C6FE97FE1EFEDBCD95" box="[273,332,473,493]" gridcol="1" gridrow="3" pageId="7" pageNumber="1298">177</td>
<td id="76D05D99F51CF6C6FEFAFE1EFE3BCD95" box="[380,428,473,493]" gridcol="2" gridrow="3" pageId="7" pageNumber="1298">88</td>
<td id="76D05D99F51CF6C6FE59FE1EFD93CD95" box="[479,516,473,493]" gridcol="3" gridrow="3" pageId="7" pageNumber="1298">40</td>
<td id="76D05D99F51CF6C6FDBCFE1EFDF3CD95" box="[570,612,473,493]" gridcol="4" gridrow="3" pageId="7" pageNumber="1298">13</td>
<td id="76D05D99F51CF6C6FD1BFE1EFD2CCD95" box="[669,699,473,493]" gridcol="5" gridrow="3" pageId="7" pageNumber="1298">2</td>
<td id="76D05D99F51CF6C6FD69FE1EFCB3CD95" box="[751,804,473,493]" gridcol="6" gridrow="3" pageId="7" pageNumber="1298">7.5</td>
<td id="76D05D99F51CF6C6FCCEFE1EFC11CD95" box="[840,902,473,493]" gridcol="7" gridrow="3" pageId="7" pageNumber="1298">2</td>
<td id="76D05D99F51CF6C6FC29FE1EFC4ECD95" box="[943,985,473,493]" gridcol="8" gridrow="3" pageId="7" pageNumber="1298">12.5</td>
<td id="76D05D99F51CF6C6FB95FE1EFBA6CD95" box="[1043,1073,473,493]" gridcol="9" gridrow="3" pageId="7" pageNumber="1298">7.5</td>
<td id="76D05D99F51CF6C6FBECFE1EFB03CD95" box="[1130,1172,473,493]" gridcol="10" gridrow="3" pageId="7" pageNumber="1298">15.5</td>
<td id="76D05D99F51CF6C6FB42FE1EFB62CD95" box="[1220,1269,473,493]" gridcol="11" gridrow="3" pageId="7" pageNumber="1298">24</td>
<td id="76D05D99F51CF6C6FA9BFE1EFACBCD95" box="[1309,1372,473,493]" gridcol="12" gridrow="3" pageId="7" pageNumber="1298">15</td>
<td id="76D05D99F51CF6C6FA0EFE1EFA02CD95" box="[1416,1429,473,493]" gridcol="13" gridrow="3" pageId="7" pageNumber="1298">2</td>
</tr>
<tr id="350134E5F51CF6C6FF00FE36FA02CE7D" box="[134,1429,497,517]" gridrow="4" pageId="7" pageNumber="1298">
<th id="76D05D99F51CF6C6FF00FE36FF4BCE7D" box="[134,220,497,517]" gridcol="0" gridrow="4" pageId="7" pageNumber="1298">
<accessionNumber id="9462AB44F51C093EFF00FE36FF58CE7D" box="[134,207,497,517]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="7" pageNumber="1298" type="EnaNcbi">V15449</accessionNumber>
</th>
<td id="76D05D99F51CF6C6FE97FE36FEDBCE7D" box="[273,332,497,517]" gridcol="1" gridrow="4" pageId="7" pageNumber="1298">217</td>
<td id="76D05D99F51CF6C6FEFAFE36FE3BCE7D" box="[380,428,497,517]" gridcol="2" gridrow="4" pageId="7" pageNumber="1298">107</td>
<td id="76D05D99F51CF6C6FE59FE36FD93CE7D" box="[479,516,497,517]" gridcol="3" gridrow="4" pageId="7" pageNumber="1298">51</td>
<td id="76D05D99F51CF6C6FDBCFE36FDF3CE7D" box="[570,612,497,517]" gridcol="4" gridrow="4" pageId="7" pageNumber="1298">20</td>
<td id="76D05D99F51CF6C6FD1BFE36FD2CCE7D" box="[669,699,497,517]" gridcol="5" gridrow="4" pageId="7" pageNumber="1298">2.5</td>
<td id="76D05D99F51CF6C6FD69FE36FCB3CE7D" box="[751,804,497,517]" gridcol="6" gridrow="4" pageId="7" pageNumber="1298">8</td>
<td id="76D05D99F51CF6C6FCCEFE36FC11CE7D" box="[840,902,497,517]" gridcol="7" gridrow="4" pageId="7" pageNumber="1298">3</td>
<td id="76D05D99F51CF6C6FC29FE36FC4ECE7D" box="[943,985,497,517]" gridcol="8" gridrow="4" pageId="7" pageNumber="1298">12.5</td>
<td id="76D05D99F51CF6C6FB95FE36FBA6CE7D" box="[1043,1073,497,517]" gridcol="9" gridrow="4" pageId="7" pageNumber="1298">13</td>
<td id="76D05D99F51CF6C6FBECFE36FB03CE7D" box="[1130,1172,497,517]" gridcol="10" gridrow="4" pageId="7" pageNumber="1298">21.5</td>
<td id="76D05D99F51CF6C6FB42FE36FB62CE7D" box="[1220,1269,497,517]" gridcol="11" gridrow="4" pageId="7" pageNumber="1298">32</td>
<td id="76D05D99F51CF6C6FA9BFE36FACBCE7D" box="[1309,1372,497,517]" gridcol="12" gridrow="4" pageId="7" pageNumber="1298">18</td>
<td id="76D05D99F51CF6C6FA0EFE36FA02CE7D" box="[1416,1429,497,517]" gridcol="13" gridrow="4" pageId="7" pageNumber="1298">3</td>
</tr>
</table>
</paragraph>
<paragraph id="8B8E36A7F51C093EFF02FD91FD5ECF08" blockId="7.[130,777,598,2027]" pageId="7" pageNumber="1298">
extant lampreys. We note that these muscle-supporting bars are not seen in lamprey larvae but exist later in adult forms (Hardisty 1981;
<bibRefCitation id="EFA04B56F51C093EFEBDFD51FE51CEC8" author="JANVIER P." box="[315,454,662,688]" pageId="7" pageNumber="1298" pagination="131 - 188" refId="ref12070" refString="JANVIER P. 1993. - Patterns of diversity in the skull of jawless fishes, in HANKEN J. &amp; HALL B. K. (eds), The Skull. University of Chicago Press, Chicago: 131 - 188." type="book chapter" year="1993">
<date id="FF8F1067F51C093EFEBDFD51FE51CEC8" box="[315,454,662,688]" pageId="7" pageNumber="1298" value="1993-01">Janvier 1993</date>
</bibRefCitation>
,
<bibRefCitation id="EFA04B56F51C093EFE53FD51FD9ACEC8" author="JANVIER P." box="[469,525,662,688]" pageId="7" pageNumber="1298" pagination="1045 - 1056" refId="ref12202" refString="JANVIER P. 2008. - Early jawless vertebrates and cyclostome origins. Zoological Science 25: 1045 - 1056. https: // doi. org / 10.2108 / zsj. 25.1045" type="journal article" year="2008">2008</bibRefCitation>
). The branchial basket is relatively well preserved in the Devonian lamprey
<taxonomicName id="4C314D24F51C093EFD45FD71FDA1CE97" authority="Gess, Coates &amp; Rubidge, 2006" authorityName="Gess, Coates &amp; Rubidge" authorityYear="2006" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Priscomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFD45FD71FF5ECE97" italics="true" pageId="7" pageNumber="1298">Priscomyzon</emphasis>
<bibRefCitation id="EFA04B56F51C093EFF55FD11FDA1CE97" author="GESS R. W. &amp; COATES M. I. &amp; RUBIDGE B. S." box="[211,566,725,752]" pageId="7" pageNumber="1298" pagination="981 - 984" refId="ref11795" refString="GESS R. W., COATES M. I. &amp; RUBIDGE B. S. 2006. - A lamprey from the Devonian period of Southern Africa. Nature 443: 981 - 984. https: // doi. org / 10.1038 / nature 05150" type="journal article" year="2006">Gess, Coates &amp; Rubidge, 2006</bibRefCitation>
</taxonomicName>
(
<bibRefCitation id="EFA04B56F51C093EFDCEFD11FC97CE97" author="GESS R. W. &amp; COATES M. I. &amp; RUBIDGE B. S." box="[584,768,725,752]" pageId="7" pageNumber="1298" pagination="981 - 984" refId="ref11795" refString="GESS R. W., COATES M. I. &amp; RUBIDGE B. S. 2006. - A lamprey from the Devonian period of Southern Africa. Nature 443: 981 - 984. https: // doi. org / 10.1038 / nature 05150" type="journal article" year="2006">
Gess
<emphasis id="B945EAB5F51C093EFD03FD11FD2ACE97" box="[645,701,725,751]" italics="true" pageId="7" pageNumber="1298">et al.</emphasis>
2006
</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFF02FD32FEFACF77" author="MIYASHITA T. &amp; GESS R. W. &amp; TIETJEN K. &amp; COATES M. I." box="[132,365,757,783]" pageId="7" pageNumber="1298" pagination="408 - 412" refId="ref12907" refString="MIYASHITA T., GESS R. W., TIETJEN K. &amp; COATES M. I. 2021. - Non-ammocoete larvae of Palaeozoic stem lampreys. Nature 591: 408 - 412. https: // doi. org / 10.1038 / s 41586 - 021 - 03305 - 9" type="journal article" year="2021">
Miyashita
<emphasis id="B945EAB5F51C093EFF7EFD31FEBACF77" box="[248,301,757,783]" italics="true" pageId="7" pageNumber="1298">et al.</emphasis>
2021
</bibRefCitation>
); however, its ventral part is also different from its analogue in
<taxonomicName id="4C314D24F51C093EFE2BFCD1FDB3CF57" authorityName="Chang, Zhang &amp; Miao" authorityYear="2006" box="[429,548,790,815]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFE2BFCD1FDB3CF57" box="[429,548,790,815]" italics="true" pageId="7" pageNumber="1298">Mesomyzon</emphasis>
</taxonomicName>
. There appears to be no bifurcation of the gill arch below the hypotrematic bar in
<taxonomicName id="4C314D24F51C093EFF05FC91FE94CF17" authorityName="Gess, Coates &amp; Rubidge" authorityYear="2006" box="[131,259,854,879]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Priscomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFF05FC91FE94CF17" box="[131,259,854,879]" italics="true" pageId="7" pageNumber="1298">Priscomyzon</emphasis>
</taxonomicName>
(
<bibRefCitation id="EFA04B56F51C093EFE92FC92FE28CF17" author="GESS R. W. &amp; COATES M. I. &amp; RUBIDGE B. S." box="[276,447,853,879]" pageId="7" pageNumber="1298" pagination="981 - 984" refId="ref11795" refString="GESS R. W., COATES M. I. &amp; RUBIDGE B. S. 2006. - A lamprey from the Devonian period of Southern Africa. Nature 443: 981 - 984. https: // doi. org / 10.1038 / nature 05150" type="journal article" year="2006">
Gess
<emphasis id="B945EAB5F51C093EFECBFC91FE17CF17" box="[333,384,853,879]" italics="true" pageId="7" pageNumber="1298">et al.</emphasis>
2006
</bibRefCitation>
; Miyashista
<emphasis id="B945EAB5F51C093EFDC1FC91FDECCF17" box="[583,635,853,879]" italics="true" pageId="7" pageNumber="1298">et al.</emphasis>
2021).
</paragraph>
<paragraph id="8B8E36A7F51C093EFF1DFCB2FE3DCF96" blockId="7.[130,777,598,2027]" pageId="7" pageNumber="1298">More dorsally, the longitudinal hypotrematic bar, the epitrematic bar and the sub-chordal rod of the branchial basket are either blurred by the gill tissues or not observable in available fossil materials.</paragraph>
<paragraph id="8B8E36A7F51C093EFF1DFC33FEBAC8D6" blockId="7.[130,777,598,2027]" pageId="7" pageNumber="1298">
The external openings of the branchial apparatus are arranged in a posteriorly slanting line (
<figureCitation id="130A2A22F51C093EFE4FFBD3FDB7C856" box="[457,544,1044,1070]" captionStart="FIG" captionStartId="8.[132,143,1381,1399]" captionTargetBox="[132,1455,215,1322]" captionTargetId="figure-353@8.[132,1455,214,1339]" captionTargetPageId="8" captionText="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="7" pageNumber="1298">Figs 2C</figureCitation>
;
<figureCitation id="130A2A22F51C093EFDA8FBD3FDC7C857" box="[558,592,1044,1071]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="7" pageNumber="1298">3B</figureCitation>
). Their posterior rims are usually more visible (darker) than the anterior rims, which might be resultant from the existence of the papillae in the posterior edge (
<bibRefCitation id="EFA04B56F51C093EFEEAFBB3FD1EC8F7" author="MARINELLI W. &amp; STRENGER A." box="[364,649,1140,1167]" pageId="7" pageNumber="1298" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
: figs 13-15, 37, 38, 40, 41).
</paragraph>
<paragraph id="8B8E36A7F51C093EFF02FB73FE60CA55" blockId="7.[130,777,598,2027]" pageId="7" pageNumber="1298">
Relative to the eyes, the branchial apparatus is more posteriorly positioned in
<taxonomicName id="4C314D24F51C093EFEEEFB13FE75C895" authorityName="Chang, Zhang &amp; Miao" authorityYear="2006" box="[360,482,1236,1261]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFEEEFB13FE75C895" box="[360,482,1236,1261]" italics="true" pageId="7" pageNumber="1298">Mesomyzon</emphasis>
</taxonomicName>
than in its Paleozoic relatives, whose branchial region extends forward nearly below the eyes (
<bibRefCitation id="EFA04B56F51C093EFF6AFAD4FD96C955" author="BARDACK D. &amp; ZANGERL R." box="[236,513,1299,1326]" pageId="7" pageNumber="1298" pagination="1265 - 1267" refId="ref11425" refString="BARDACK D. &amp; ZANGERL R. 1968. - First fossil lamprey: a record from the Pennsylvanian of Illinois. Science 162: 1265 - 1267. https: // doi. org / 10.1126 / science. 162.3859.126" type="journal article" year="1968">Bardack &amp; Zangerl 1968</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFD97FAD4FC97C956" author="JANVIER P. &amp; LUND R." box="[529,768,1299,1326]" pageId="7" pageNumber="1298" pagination="407 - 413" refId="ref12269" refString="JANVIER P. &amp; LUND R. 1983. - Hardistiella montanensis n. gen. et sp. (Petromyzontida) from the Lower Carboniferous of Montana, with remarks on the affinities of the lampreys. Journal of Vertebrate Paleontology 2: 407 - 413. https: // doi. org / 10.1080 / 027246 34.1983. 1001194" type="journal article" year="1983">Janvier &amp; Lund 1983</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFF02FAF4FEF9C935" author="LUND R. &amp; JANVIER P." box="[132,366,1331,1357]" pageId="7" pageNumber="1298" pagination="647 - 652" refId="ref12673" refString="LUND R. &amp; JANVIER P. 1986. - A second lamprey from the Lower Carboniferous (Namurian) of Bear Gulch, Montana (U. S. A.). Geobios 19: 647 - 652. https: // doi. org / 10.1016 / s 0016 - 6995 (86) 80061 - 4" type="journal article" year="1986">
Lund &amp;
<date id="FF8F1067F51C093EFF62FAF4FEF9C935" box="[228,366,1331,1357]" pageId="7" pageNumber="1298" value="1986-01">Janvier 1986</date>
</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFEFAFAF4FD92C935" author="JANVIER P." box="[380,517,1331,1357]" pageId="7" pageNumber="1298" pagination="1045 - 1056" refId="ref12202" refString="JANVIER P. 2008. - Early jawless vertebrates and cyclostome origins. Zoological Science 25: 1045 - 1056. https: // doi. org / 10.2108 / zsj. 25.1045" type="journal article" year="2008">
<date id="FF8F1067F51C093EFEFAFAF4FD92C935" box="[380,517,1331,1357]" pageId="7" pageNumber="1298" value="2008-01">Janvier 2008</date>
</bibRefCitation>
) or even anterior to the eyes (
<bibRefCitation id="EFA04B56F51C093EFF39FA94FE37C915" author="MIYASHITA T. &amp; GESS R. W. &amp; TIETJEN K. &amp; COATES M. I." box="[191,416,1363,1389]" pageId="7" pageNumber="1298" pagination="408 - 412" refId="ref12907" refString="MIYASHITA T., GESS R. W., TIETJEN K. &amp; COATES M. I. 2021. - Non-ammocoete larvae of Palaeozoic stem lampreys. Nature 591: 408 - 412. https: // doi. org / 10.1038 / s 41586 - 021 - 03305 - 9" type="journal article" year="2021">
Miyashita
<emphasis id="B945EAB5F51C093EFEB6FA93FEF4C915" box="[304,355,1363,1389]" italics="true" pageId="7" pageNumber="1298">et al.</emphasis>
2021
</bibRefCitation>
). The majority of living lampreys have a slightly more anteriorly located branchial region than in
<taxonomicName id="4C314D24F51C093EFF25FA53FE8CC9D5" authorityName="Chang, Zhang &amp; Miao" authorityYear="2006" box="[163,283,1428,1453]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFF25FA53FE8CC9D5" box="[163,283,1428,1453]" italics="true" pageId="7" pageNumber="1298">Mesomyzon</emphasis>
</taxonomicName>
, except for quite a few parasitic species, i.e.,
<taxonomicName id="4C314D24F51C093EFF00FA74FDDEC9B5" authority="(Bond &amp; Kan, 1973)" baseAuthorityName="Bond &amp; Kan" baseAuthorityYear="1973" box="[134,585,1459,1485]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Entosphenus" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="species" species="minimus">
<emphasis id="B945EAB5F51C093EFF00FA74FEF1C9B5" box="[134,358,1459,1485]" italics="true" pageId="7" pageNumber="1298">Entosphenus minimus</emphasis>
(Bond &amp; Kan, 1973)
</taxonomicName>
,
<taxonomicName id="4C314D24F51C093EFDD2FA73FE04C995" authority="Kux &amp; Steiner, 1972" authorityName="Kux &amp; Steiner" authorityYear="1972" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Lampetra" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="species" species="lanceolata">
<emphasis id="B945EAB5F51C093EFDD2FA73FF3BC995" italics="true" pageId="7" pageNumber="1298">Lampetra lanceolata</emphasis>
Kux &amp; Steiner, 1972
</taxonomicName>
, which display a similar postocular length (the distance between the eyes and the first gill opening) to
<taxonomicName id="4C314D24F51C093EFF52F9D4FE65CA55" authority="(Renaud 2011)" baseAuthorityName="Renaud" baseAuthorityYear="2011" box="[212,498,1554,1581]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFF52F9D4FEDBCA54" box="[212,332,1555,1580]" italics="true" pageId="7" pageNumber="1298">Mesomyzon</emphasis>
(
<bibRefCitation id="EFA04B56F51C093EFED2F9D5FE70CA55" author="RENAUD C. B." box="[340,487,1554,1581]" pageId="7" pageNumber="1298" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
)
</taxonomicName>
.
</paragraph>
<paragraph id="8B8E36A7F51C093EFF1DF9F5FADFCF08" blockId="7.[130,777,598,2027]" lastBlockId="7.[812,1455,598,880]" pageId="7" pageNumber="1298">
The ratio of prebranchial length/ branchial length in
<taxonomicName id="4C314D24F51C093EFD53F9F4FF44CA14" baseAuthorityName="Renaud" baseAuthorityYear="2011" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFD53F9F4FF44CA14" italics="true" pageId="7" pageNumber="1298">Mesomyzon</emphasis>
</taxonomicName>
ranges from 1.4 to 1.8, a similar state as in Paleozoic lampreys (
<bibRefCitation id="EFA04B56F51C093EFF73F9B5FD91CAF4" author="BARDACK D. &amp; ZANGERL R." box="[245,518,1650,1676]" pageId="7" pageNumber="1298" pagination="1265 - 1267" refId="ref11425" refString="BARDACK D. &amp; ZANGERL R. 1968. - First fossil lamprey: a record from the Pennsylvanian of Illinois. Science 162: 1265 - 1267. https: // doi. org / 10.1126 / science. 162.3859.126" type="journal article" year="1968">Bardack &amp; Zangerl 1968</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFD92F9B5FC97CAF4" author="JANVIER P. &amp; LUND R." box="[532,768,1650,1676]" pageId="7" pageNumber="1298" pagination="407 - 413" refId="ref12269" refString="JANVIER P. &amp; LUND R. 1983. - Hardistiella montanensis n. gen. et sp. (Petromyzontida) from the Lower Carboniferous of Montana, with remarks on the affinities of the lampreys. Journal of Vertebrate Paleontology 2: 407 - 413. https: // doi. org / 10.1080 / 027246 34.1983. 1001194" type="journal article" year="1983">Janvier &amp; Lund 1983</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFF02F955FEF8CAD4" author="LUND R. &amp; JANVIER P." box="[132,367,1682,1708]" pageId="7" pageNumber="1298" pagination="647 - 652" refId="ref12673" refString="LUND R. &amp; JANVIER P. 1986. - A second lamprey from the Lower Carboniferous (Namurian) of Bear Gulch, Montana (U. S. A.). Geobios 19: 647 - 652. https: // doi. org / 10.1016 / s 0016 - 6995 (86) 80061 - 4" type="journal article" year="1986">
Lund &amp;
<date id="FF8F1067F51C093EFF63F955FEF8CAD4" box="[229,367,1682,1708]" pageId="7" pageNumber="1298" value="1986-01">Janvier 1986</date>
</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFEFBF955FDBECAD4" author="GESS R. W. &amp; COATES M. I. &amp; RUBIDGE B. S." box="[381,553,1682,1708]" pageId="7" pageNumber="1298" pagination="981 - 984" refId="ref11795" refString="GESS R. W., COATES M. I. &amp; RUBIDGE B. S. 2006. - A lamprey from the Devonian period of Southern Africa. Nature 443: 981 - 984. https: // doi. org / 10.1038 / nature 05150" type="journal article" year="2006">
Gess
<emphasis id="B945EAB5F51C093EFE30F954FE7DCAD4" box="[438,490,1682,1708]" italics="true" pageId="7" pageNumber="1298">et al.</emphasis>
2006
</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFDB1F955FD56CAD4" author="JANVIER P." box="[567,705,1682,1708]" pageId="7" pageNumber="1298" pagination="1045 - 1056" refId="ref12202" refString="JANVIER P. 2008. - Early jawless vertebrates and cyclostome origins. Zoological Science 25: 1045 - 1056. https: // doi. org / 10.2108 / zsj. 25.1045" type="journal article" year="2008">
<date id="FF8F1067F51C093EFDB1F955FD56CAD4" box="[567,705,1682,1708]" pageId="7" pageNumber="1298" value="2008-01">Janvier 2008</date>
</bibRefCitation>
). This ratio in six out of all 39 living lamprey species falls within this range or slightly exceeds it (see Appendices 1; 2). It is interesting that all these six species above except for
<taxonomicName id="4C314D24F51C093EFD08F935FE77CB54" authority="Vladykov &amp; Kott, 1978" authorityName="Vladykov &amp; Kott" authorityYear="1978" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Lethenteron" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="species" species="alaskenses">
<emphasis id="B945EAB5F51C093EFD08F935FF72CB54" italics="true" pageId="7" pageNumber="1298">Lethenteron alaskenses</emphasis>
Vladykov &amp; Kott, 1978
</taxonomicName>
are parasitic (
<bibRefCitation id="EFA04B56F51C093EFDEDF8D5FD60CB54" author="RENAUD C. B." box="[619,759,1810,1836]" pageId="7" pageNumber="1298" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
). Among all living species, the non-parasitic species tend to have a smaller prebranchial length/ branchial length ratio than the parasitic ones (
<bibRefCitation id="EFA04B56F51C093EFE9DF8B6FE30CBF3" author="RENAUD C. B." box="[283,423,1905,1931]" pageId="7" pageNumber="1298" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
). The prebranchial length was also assessed in another criterion. This region in
<taxonomicName id="4C314D24F51C093EFDD0F855FD59CBD3" baseAuthorityName="Renaud" baseAuthorityYear="2011" box="[598,718,1938,1963]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFDD0F855FD59CBD3" box="[598,718,1938,1963]" italics="true" pageId="7" pageNumber="1298">Mesomyzon</emphasis>
</taxonomicName>
is no less than twice the maximal head depth. It is notably longer than that in
<taxonomicName id="4C314D24F51C093EFE86F815FD19CB93" authority="Bardack &amp; Zangerl, 1968" authorityName="Bardack &amp; Zangerl" authorityYear="1968" box="[256,654,2001,2027]" class="Cephalaspidomorphi" genus="Mayomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFE86F815FEECCB93" box="[256,379,2002,2027]" italics="true" pageId="7" pageNumber="1298">Mayomyzon</emphasis>
<bibRefCitation id="EFA04B56F51C093EFE04F816FD19CB93" author="BARDACK D. &amp; ZANGERL R." box="[386,654,2001,2027]" pageId="7" pageNumber="1298" pagination="1265 - 1267" refId="ref11425" refString="BARDACK D. &amp; ZANGERL R. 1968. - First fossil lamprey: a record from the Pennsylvanian of Illinois. Science 162: 1265 - 1267. https: // doi. org / 10.1126 / science. 162.3859.126" type="journal article" year="1968">Bardack &amp; Zangerl, 1968</bibRefCitation>
</taxonomicName>
,
<emphasis id="B945EAB5F51C093EFD13F816FC92CB93" box="[661,773,2001,2027]" italics="true" pageId="7" pageNumber="1298">Hardistella</emphasis>
<bibRefCitation id="EFA04B56F51C093EFCABFD91FB8BCE08" author="JANVIER P. &amp; LUND R." box="[813,1052,598,624]" pageId="7" pageNumber="1298" pagination="407 - 413" refId="ref12269" refString="JANVIER P. &amp; LUND R. 1983. - Hardistiella montanensis n. gen. et sp. (Petromyzontida) from the Lower Carboniferous of Montana, with remarks on the affinities of the lampreys. Journal of Vertebrate Paleontology 2: 407 - 413. https: // doi. org / 10.1080 / 027246 34.1983. 1001194" type="journal article" year="1983">Janvier &amp; Lund, 1983</bibRefCitation>
and
<taxonomicName id="4C314D24F51C093EFBD4FD90FCF4CEE8" authority="Bardack &amp; Richardson, 1977" authorityName="Bardack &amp; Richardson" authorityYear="1977" class="Cephalaspidomorphi" family="Pipisciidae" genus="Pipiscius" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFBD4FD90FB3CCE08" box="[1106,1195,599,624]" italics="true" pageId="7" pageNumber="1298">Pipiscius</emphasis>
<bibRefCitation id="EFA04B56F51C093EFB34FD91FCF4CEE8" author="BARDACK D. &amp; RICHARDSON E. S." pageId="7" pageNumber="1298" pagination="489 - 510" refId="ref11466" refString="BARDACK D. &amp; RICHARDSON E. S. 1977. - New agnathous fishes from the Pennsylvanian of Illinois. Fieldiana (Geology) 33: 489 - 510. https: // doi. org / 10.5962 / bhl. title. 5167" type="journal article" year="1977">Bardack &amp; Richardson, 1977</bibRefCitation>
</taxonomicName>
(
<bibRefCitation id="EFA04B56F51C093EFCF7FDB1FBE3CEE8" author="BARDACK D. &amp; ZANGERL R." box="[881,1140,630,656]" pageId="7" pageNumber="1298" pagination="1265 - 1267" refId="ref11425" refString="BARDACK D. &amp; ZANGERL R. 1968. - First fossil lamprey: a record from the Pennsylvanian of Illinois. Science 162: 1265 - 1267. https: // doi. org / 10.1126 / science. 162.3859.126" type="journal article" year="1968">Bardack &amp; Zangerl 1968</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFBF9FDB1FA3FCEE8" author="BARDACK D. &amp; RICHARDSON E. S." box="[1151,1448,630,656]" pageId="7" pageNumber="1298" pagination="489 - 510" refId="ref11466" refString="BARDACK D. &amp; RICHARDSON E. S. 1977. - New agnathous fishes from the Pennsylvanian of Illinois. Fieldiana (Geology) 33: 489 - 510. https: // doi. org / 10.5962 / bhl. title. 5167" type="journal article" year="1977">Bardack &amp; Richardson 1977</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFCABFD51FB86CEC8" author="JANVIER P. &amp; LUND R." box="[813,1041,662,688]" pageId="7" pageNumber="1298" pagination="407 - 413" refId="ref12269" refString="JANVIER P. &amp; LUND R. 1983. - Hardistiella montanensis n. gen. et sp. (Petromyzontida) from the Lower Carboniferous of Montana, with remarks on the affinities of the lampreys. Journal of Vertebrate Paleontology 2: 407 - 413. https: // doi. org / 10.1080 / 027246 34.1983. 1001194" type="journal article" year="1983">Janvier &amp; Lund 1983</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFB9BFD51FB32CEC8" author="JANVIER P." box="[1053,1189,662,688]" pageId="7" pageNumber="1298" pagination="1045 - 1056" refId="ref12202" refString="JANVIER P. 2008. - Early jawless vertebrates and cyclostome origins. Zoological Science 25: 1045 - 1056. https: // doi. org / 10.2108 / zsj. 25.1045" type="journal article" year="2008">
<date id="FF8F1067F51C093EFB9BFD51FB32CEC8" box="[1053,1189,662,688]" pageId="7" pageNumber="1298" value="2008-01">Janvier 2008</date>
</bibRefCitation>
).
<taxonomicName id="4C314D24F51C093EFB3CFD51FCF1CEB7" authority="Gess et al., 2006" authorityName="Gess" authorityYear="2006" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Priscomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFB3CFD51FAADCED7" box="[1210,1338,662,687]" italics="true" pageId="7" pageNumber="1298">Priscomyzon</emphasis>
<bibRefCitation id="EFA04B56F51C093EFAB9FD51FCF1CEB7" author="GESS R. W. &amp; COATES M. I. &amp; RUBIDGE B. S." pageId="7" pageNumber="1298" pagination="981 - 984" refId="ref11795" refString="GESS R. W., COATES M. I. &amp; RUBIDGE B. S. 2006. - A lamprey from the Devonian period of Southern Africa. Nature 443: 981 - 984. https: // doi. org / 10.1038 / nature 05150" type="journal article" year="2006">
Gess
<emphasis id="B945EAB5F51C093EFAF3FD51FA30CEC8" box="[1397,1447,662,688]" italics="true" pageId="7" pageNumber="1298">et al.</emphasis>
, 2006
</bibRefCitation>
</taxonomicName>
displays a prebranchial length/maximal head depth ratio of
<emphasis id="B945EAB5F51C093EFC02FD11FC1ACE97" box="[900,909,726,751]" italics="true" pageId="7" pageNumber="1298">c</emphasis>
. 2, which actually results from the enlargement of the oral disc (
<bibRefCitation id="EFA04B56F51C093EFC44FD32FBF8CF77" author="GESS R. W. &amp; COATES M. I. &amp; RUBIDGE B. S." box="[962,1135,757,783]" pageId="7" pageNumber="1298" pagination="981 - 984" refId="ref11795" refString="GESS R. W., COATES M. I. &amp; RUBIDGE B. S. 2006. - A lamprey from the Devonian period of Southern Africa. Nature 443: 981 - 984. https: // doi. org / 10.1038 / nature 05150" type="journal article" year="2006">
Gess
<emphasis id="B945EAB5F51C093EFC7AFD31FBA7CF77" box="[1020,1072,757,783]" italics="true" pageId="7" pageNumber="1298">et al.</emphasis>
2006
</bibRefCitation>
). This ratio in half of the living lampreys is smaller than that in
<taxonomicName id="4C314D24F51C093EFB2AFCD1FAB3CF57" baseAuthorityName="Renaud" baseAuthorityYear="2011" box="[1196,1316,790,815]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="7" pageNumber="1298" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F51C093EFB2AFCD1FAB3CF57" box="[1196,1316,790,815]" italics="true" pageId="7" pageNumber="1298">Mesomyzon</emphasis>
</taxonomicName>
, whereas the remaining living species (21 out of 39 species) have a ratio approximating 2 or beyond (see Appendices 1; 2).
</paragraph>
<paragraph id="8B8E36A7F51C093EFCABFC52FB9ECFD7" blockId="7.[813,1033,917,943]" box="[813,1033,917,943]" pageId="7" pageNumber="1298">
<heading id="D0C681CBF51C093EFCABFC52FB9ECFD7" box="[813,1033,917,943]" fontSize="11" level="2" pageId="7" pageNumber="1298" reason="8">
<emphasis id="B945EAB5F51C093EFCABFC52FB9ECFD7" box="[813,1033,917,943]" italics="true" pageId="7" pageNumber="1298">Pericardinal cartilage</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F51C093EFCABFC72FBD7C837" blockId="7.[810,1455,949,1103]" pageId="7" pageNumber="1298">
The pericardial cartilage is connected to the rear of the branchial basket (
<figureCitation id="130A2A22F51C093EFCF9FC13FC28CF97" box="[895,959,980,1007]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="7" pageNumber="1298">Figs 3</figureCitation>
A-F; 4D), and shows a profile of an equilateral triangle with little difference from that in living lampreys (
<figureCitation id="130A2A22F51C093EFCB0FBD3FC3AC857" box="[822,941,1044,1071]" captionStart="FIG" captionStartId="6.[132,143,1916,1934]" captionTargetId="figure-32@6.[698,1267,769,1325]" captionTargetPageId="6" captionText="FIG. 1. — Generalized anatomy of living lampreys: A, schematic sagittal section through head and pharyngeal region; the vessels, esophagus, respiratory tube, and parts of the heart are shown with portions cut away, rather than in sagittal section; redrawn after De Iuliis &amp; Pulerà 2011, with the structures of the nasohypophysial complex labelled after Janvier 1974; B, the cranial skeleton of an adult lamprey, redrawn after Hardisty &amp; Potter 1981; C, arrangement pattern of the cranial nerves, redrawn after Marinelli &amp; Strenger 1954; D, oral disc of an adult lamprey showing the keratinous teeth and other associated structures. The dotted lines delineate the various fields. Redrawn after Renaud 2011." figureDoi="http://doi.org/10.5281/zenodo.5767846" httpUri="https://zenodo.org/record/5767846/files/figure.png" pageId="7" pageNumber="1298">Fig. 1A, B</figureCitation>
and
<bibRefCitation id="EFA04B56F51C093EFC6AFBD3FA8AC857" author="MARINELLI W. &amp; STRENGER A." box="[1004,1309,1044,1071]" pageId="7" pageNumber="1298" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
: figs 59, 60;
<bibRefCitation id="EFA04B56F51C093EFCA9FBF3FBA7C836" author="HARDISTY M. W. &amp; POTTER I. C." box="[815,1072,1076,1103]" pageId="7" pageNumber="1298" pagination="118 - 124" refId="ref11958" refString="HARDISTY M. W. &amp; POTTER I. C. 1981. - The skeleton, in The biology of lampreys. in HARDISTY M. W. &amp; POTTER I. C. (eds), The Biology of Lampreys. Volume 3. Academic Press, New York: 118 - 124." type="book chapter" year="1981">Hardisty &amp; Potter 1981</bibRefCitation>
).
</paragraph>
<paragraph id="8B8E36A7F51C093EFCABFBB2FC13C8F6" blockId="7.[813,900,1141,1166]" box="[813,900,1141,1166]" pageId="7" pageNumber="1298">
<heading id="D0C681CBF51C093EFCABFBB2FC13C8F6" box="[813,900,1141,1166]" fontSize="11" level="2" pageId="7" pageNumber="1298" reason="8">
<emphasis id="B945EAB5F51C093EFCABFBB2FC13C8F6" box="[813,900,1141,1166]" italics="true" pageId="7" pageNumber="1298">Intestine</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F51C093EFCABFB53FA32CA94" blockId="7.[811,1457,1172,2028]" pageId="7" pageNumber="1298">
The accurate morphology of the intestine cannot be determined; however, its position can be traced by the arrangement of the detrital gobbets occasionally preserved in some large adult specimens. Judging from the detritus preserved immediately behind the last gill pouch (
<figureCitation id="130A2A22F51C093EFB17FAD4FA93C956" box="[1169,1284,1299,1326]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="7" pageNumber="1298">Fig. 3C, D</figureCitation>
), the intestine is arranged in a similar pattern as in living adult lampreys (
<figureCitation id="130A2A22F51C093EFAE2FAF4FA38C936" box="[1380,1455,1331,1358]" captionStart="FIG" captionStartId="6.[132,143,1916,1934]" captionTargetId="figure-32@6.[698,1267,769,1325]" captionTargetPageId="6" captionText="FIG. 1. — Generalized anatomy of living lampreys: A, schematic sagittal section through head and pharyngeal region; the vessels, esophagus, respiratory tube, and parts of the heart are shown with portions cut away, rather than in sagittal section; redrawn after De Iuliis &amp; Pulerà 2011, with the structures of the nasohypophysial complex labelled after Janvier 1974; B, the cranial skeleton of an adult lamprey, redrawn after Hardisty &amp; Potter 1981; C, arrangement pattern of the cranial nerves, redrawn after Marinelli &amp; Strenger 1954; D, oral disc of an adult lamprey showing the keratinous teeth and other associated structures. The dotted lines delineate the various fields. Redrawn after Renaud 2011." figureDoi="http://doi.org/10.5281/zenodo.5767846" httpUri="https://zenodo.org/record/5767846/files/figure.png" pageId="7" pageNumber="1298">Fig.1A</figureCitation>
and
<bibRefCitation id="EFA04B56F51C093EFCDBFA94FB14C916" author="MARINELLI W. &amp; STRENGER A." box="[861,1155,1363,1390]" pageId="7" pageNumber="1298" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
). The preserved part of the detrital crumbs consists of coarse sand grains of variable sizes and their presence in the digestive tube possibly hints at the fossil lamprey’s habit of attaching on stones or moving stones with their oral disc for nesting (
<bibRefCitation id="EFA04B56F51C093EFBE9FA14FA90C995" author="HARDISTY M. W." box="[1135,1287,1491,1517]" pageId="7" pageNumber="1298" refId="ref11843" refString="HARDISTY M. W. 1979. - Biology of Cyclostomes. Chapman and Hall, London." type="book" year="1979">Hardisty 1979</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFA94FA14FA37C995" author="RENAUD C. B." box="[1298,1440,1491,1517]" pageId="7" pageNumber="1298" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
), or alternatively the habit of burying themselves in the substrate when the mucus secreted by the oral fimbriae trapped the sand and silt, just like the case in some living lampreys (
<bibRefCitation id="EFA04B56F51C093EFCB0F995FBA4CA14" author="KHIDIR K. T. &amp; RENAUD C. B." box="[822,1075,1618,1644]" pageId="7" pageNumber="1298" pagination="271 - 278" refId="ref12506" refString="KHIDIR K. T. &amp; RENAUD C. B. 2003. - Oral fimbriae and papillae in parasitic lampreys (Petromyzontiformes). Environmental Biology of Fishes 66: 271 - 278. https: // doi. org / 10.1023 / A: 1023961910547" type="journal article" year="2003">Khidir &amp; Renaud 2003</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFBC6F995FB45CA14" author="RENAUD C. B." box="[1088,1234,1618,1644]" pageId="7" pageNumber="1298" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
). In IVPP
<accessionNumber id="9462AB44F51C093EFACFF994FA3CCA15" box="[1353,1451,1618,1645]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="7" pageNumber="1298" type="EnaNcbi">V 15449</accessionNumber>
, there is a mass of detritus preserved between the buccal funnel and the pharyngeal cavity, which might locate the mouth (
<figureCitation id="130A2A22F51C093EFCB0F975FC3DCAB5" box="[822,938,1714,1741]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="7" pageNumber="1298">Fig. 3C, D</figureCitation>
). The ending of the intestine, the cloaca (anus) is located at the level of the peak of the “posterior dorsal fin”.
</paragraph>
<paragraph id="8B8E36A7F51C093EFCC5F935FBD9CB94" blockId="7.[811,1457,1172,2028]" pageId="7" pageNumber="1298">
The liver can be detected just behind the pericardial cartilage in several specimens (
<figureCitation id="130A2A22F51C093EFBDFF8D5FB7ECB54" box="[1113,1257,1810,1836]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="7" pageNumber="1298">Fig. 3A, E, F</figureCitation>
). It shows a triangular profile and this part is always in a brightly red in color on the matrix (e.g., in IVPP
<accessionNumber id="9462AB44F51C093EFBF7F895FB41CB14" box="[1137,1238,1873,1900]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15448" pageId="7" pageNumber="1298" type="EnaNcbi">V 15448</accessionNumber>
A), which might be related with the oxidized iron ion (of the blood) originally concentrated in the liver organ. This is a similar preservation pattern interpreted in several agnathan fossils (
<bibRefCitation id="EFA04B56F51C093EFA99F876FA3FCBB3" author="JANVIER P." box="[1311,1448,1969,1995]" pageId="7" pageNumber="1298" refId="ref12114" refString="JANVIER P. 1996. - Early Vertebrates. Clarendon Press, Oxford: 393 p." type="book" year="1996">
<date id="FF8F1067F51C093EFA99F876FA3FCBB3" box="[1311,1448,1969,1995]" pageId="7" pageNumber="1298" value="1996-01">Janvier 1996</date>
</bibRefCitation>
;
<bibRefCitation id="EFA04B56F51C093EFCABF815FBA9CB93" author="NEWMAN M. J. &amp; TREWIN N. H." box="[813,1086,2001,2028]" pageId="7" pageNumber="1298" pagination="43 - 51" refId="ref12960" refString="NEWMAN M. J. &amp; TREWIN N. H. 2001. - A new jawless vertebrate from the Middle Devonian of Scotland. Palaeontology 44: 43 - 51. https: // doi. org / 10.1111 / 1475 - 4983.00168" type="journal article" year="2001">Newman &amp; Trewin 2001</bibRefCitation>
).
</paragraph>
<caption id="DF4E662FF5130931FF02FAA2FEE8C9C3" ID-DOI="http://doi.org/10.5281/zenodo.5764681" ID-Zenodo-Dep="5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="8" pageNumber="1299" startId="8.[132,143,1381,1399]" targetBox="[132,1455,215,1322]" targetPageId="8">
<paragraph id="8B8E36A7F5130931FF02FAA2FEE8C9C3" blockId="8.[132,1455,1381,1467]" pageId="8" pageNumber="1299">
FIG. 2. —
<taxonomicName id="4C314D24F5130931FF55FAA2FDF9C90F" authority="Chang, Zhang &amp; Miao, 2006" authorityName="Chang, Zhang &amp; Miao" authorityYear="2006" box="[211,622,1381,1399]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="8" pageNumber="1299" phylum="Chordata" rank="species" species="mengae">
<emphasis id="B945EAB5F5130931FF55FAA2FEE8C90F" box="[211,383,1381,1399]" italics="true" pageId="8" pageNumber="1299">Mesomyzon mengae</emphasis>
<bibRefCitation id="EFA04B56F5130931FE05FAA2FDF9C90F" author="CHANG M. - M. &amp; ZHANG J. Y. &amp; MIAO D. S." box="[387,622,1381,1399]" pageId="8" pageNumber="1299" pagination="972 - 974" refId="ref11511" refString="CHANG M. - M., ZHANG J. Y. &amp; MIAO D. S. 2006. - A lamprey from the Cretaceous Jehol biota of China. Nature 441: 972 - 974. https: // doi. org / 10.1038 / nature 04730" type="journal article" year="2006">Chang, Zhang &amp; Miao, 2006</bibRefCitation>
</taxonomicName>
, new adult individuals and morphological restoration:
<emphasis id="B945EAB5F5130931FBACFAA2FBA0C90F" bold="true" box="[1066,1079,1381,1399]" pageId="8" pageNumber="1299">A</emphasis>
, photograph of IVPP
<accessionNumber id="9462AB44F5130931FB6FFAA2FAA7C90F" box="[1257,1328,1381,1399]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15027" pageId="8" pageNumber="1299" type="EnaNcbi">V 15027</accessionNumber>
;
<emphasis id="B945EAB5F5130931FAB1FAA2FAD3C90F" bold="true" box="[1335,1348,1381,1399]" pageId="8" pageNumber="1299">B</emphasis>
, photograph of IVPP
<accessionNumber id="9462AB44F5130931FF41FABBFE98C9F6" box="[199,271,1404,1422]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="8" pageNumber="1299" type="EnaNcbi">V 15449</accessionNumber>
;
<emphasis id="B945EAB5F5130931FE90FABCFEB3C9F5" bold="true" box="[278,292,1403,1421]" pageId="8" pageNumber="1299">C</emphasis>
, photograph of IVPP
<accessionNumber id="9462AB44F5130931FE5EFABBFD88C9F6" box="[472,543,1404,1422]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V14981" pageId="8" pageNumber="1299" type="EnaNcbi">V 14981</accessionNumber>
B;
<emphasis id="B945EAB5F5130931FDB5FABBFDD6C9F6" bold="true" box="[563,577,1404,1422]" pageId="8" pageNumber="1299">D</emphasis>
, restoration of the general appearance of
<taxonomicName id="4C314D24F5130931FC19FABBFB94C9F6" baseAuthorityName="Renaud" baseAuthorityYear="2011" box="[927,1027,1404,1422]" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Mesomyzon" higherTaxonomySource="GBIF" kingdom="Animalia" order="Petromyzontiformes" pageId="8" pageNumber="1299" phylum="Chordata" rank="genus">
<emphasis id="B945EAB5F5130931FC19FABBFB94C9F6" box="[927,1027,1404,1422]" italics="true" pageId="8" pageNumber="1299">Mesomyzon</emphasis>
</taxonomicName>
, dotted circle behind the eyes representing the otic capsule. Abbreviations:
<emphasis id="B945EAB5F5130931FECBFA55FEFEC9DC" bold="true" box="[333,361,1426,1444]" pageId="8" pageNumber="1299">adf</emphasis>
, anterior dorsal fin;
<emphasis id="B945EAB5F5130931FD94FA55FDBEC9DC" bold="true" box="[530,553,1426,1444]" pageId="8" pageNumber="1299">bp</emphasis>
, branchial pouches;
<emphasis id="B945EAB5F5130931FD5EFA55FD7EC9DC" bold="true" box="[728,745,1426,1444]" pageId="8" pageNumber="1299">cf</emphasis>
, caudal fin;
<emphasis id="B945EAB5F5130931FCD6FA55FCF7C9DC" bold="true" box="[848,864,1426,1444]" pageId="8" pageNumber="1299">cl</emphasis>
, cloaca;
<emphasis id="B945EAB5F5130931FC2BFA55FC2FC9DC" bold="true" box="[941,952,1426,1444]" pageId="8" pageNumber="1299">e</emphasis>
, eye(s);
<emphasis id="B945EAB5F5130931FC7BFA55FB88C9DC" bold="true" box="[1021,1055,1426,1444]" pageId="8" pageNumber="1299">egp</emphasis>
, external gill pores;
<emphasis id="B945EAB5F5130931FB4FFA55FB77C9DC" bold="true" box="[1225,1248,1426,1444]" pageId="8" pageNumber="1299">od</emphasis>
, oral disc;
<emphasis id="B945EAB5F5130931FABBFA55FACDC9DC" bold="true" box="[1341,1370,1426,1444]" pageId="8" pageNumber="1299">pdf</emphasis>
, posterior dorsal fin. Scale bars: 10 mm.
</paragraph>
</caption>
<paragraph id="8B8E36A7F5130931FF02FA34FF22CA73" blockId="8.[131,777,1523,2028]" box="[132,181,1523,1549]" pageId="8" pageNumber="1299">FINS</paragraph>
<paragraph id="8B8E36A7F5130931FF02F9D5FEFBCA55" blockId="8.[131,777,1523,2028]" box="[132,364,1554,1581]" pageId="8" pageNumber="1299">
<emphasis id="B945EAB5F5130931FF02F9D5FEFBCA55" box="[132,364,1554,1581]" italics="true" pageId="8" pageNumber="1299">Dorsal and caudal fins</emphasis>
</paragraph>
<paragraph id="8B8E36A7F5130930FF02F9F4FEEDCD6A" blockId="8.[131,777,1523,2028]" lastBlockId="9.[131,775,215,816]" lastPageId="9" lastPageNumber="1300" pageId="8" pageNumber="1299">
Here we hold the assumption proposed by
<bibRefCitation id="EFA04B56F5130931FDEDF9F5FF51CA15" author="JANVIER P." pageId="8" pageNumber="1299" pagination="1045 - 1056" refId="ref12202" refString="JANVIER P. 2008. - Early jawless vertebrates and cyclostome origins. Zoological Science 25: 1045 - 1056. https: // doi. org / 10.2108 / zsj. 25.1045" type="journal article" year="2008">Janvier (2008: 1051)</bibRefCitation>
that the so-called “posterior dorsal fin” in lampreys should represent the anterior part of the caudal epichordal lobe inserted on the markedly hypocercal tail and this issue will be referred to in the discussion section below. The anterior dorsal fin is so long that it extends anteriorly as far as to the level of the anterior edge of the fourth gill pouch. Its occupies 44%-48% of the total body length and the height occupies
<emphasis id="B945EAB5F5130931FF60F8F5FF78CB33" box="[230,239,1842,1867]" italics="true" pageId="8" pageNumber="1299">c</emphasis>
. 50% of the maximal body depth. The fin changes little in height along its whole length, except that it is beveled smoothly at both ends. The anterior dorsal fin and the “posterior dorsal fin” are usually separated by a distance slightly smaller than the body depth in this position, except for
<specimenCount id="9D37FD2EF5130931FD66F875FF7ECB93" pageId="8" pageNumber="1299" type="generic">one specimen</specimenCount>
(IVPP
<accessionNumber id="9462AB44F5130931FEB1F815FE01CB94" box="[311,406,2001,2028]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15448" pageId="8" pageNumber="1299" type="EnaNcbi">V 15448</accessionNumber>
A), where the base of the “posterior dorsal fin” extends anteriorly to touch the anterior dorsal fin and this connecting part lacks fin radials. This variation of “posterior dorsal fin” might be correlated with a sexual maturity or mating behavior, because this fin in living lampreys serves as a “brake” to present the male’s tightly wound tail from gliding backward over the female’s body during the mating act (Vladykov 197) and before the breeding season, the female (and sometimes the male) develops a swelling in the anterior edge of this fin (
<bibRefCitation id="EFA04B56F5130931FBD9F935FAD2CB74" author="JANVIER P. &amp; LUND R." box="[1119,1349,1778,1804]" pageId="8" pageNumber="1299" pagination="407 - 413" refId="ref12269" refString="JANVIER P. &amp; LUND R. 1983. - Hardistiella montanensis n. gen. et sp. (Petromyzontida) from the Lower Carboniferous of Montana, with remarks on the affinities of the lampreys. Journal of Vertebrate Paleontology 2: 407 - 413. https: // doi. org / 10.1080 / 027246 34.1983. 1001194" type="journal article" year="1983">Janvier &amp; Lund 1983</bibRefCitation>
: fig. 4f1). The chordal lobe of the tail is titled downwards at the position of the cloaca (anus). This feature is more marked than in extant lampreys (
<bibRefCitation id="EFA04B56F5130931FB96F896FB3FCB14" author="RENAUD C. B." box="[1040,1192,1873,1900]" pageId="8" pageNumber="1299" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
). The “posterior dorsal fin” is mostly surmounted on the tail, roughly triangular in shape and notably higher than the anterior dorsal fin. More posteriorly, it is continuous with the posterior lobe of the caudal fin via a smoothly round notch. The posterior lobe is spade-like in shape with the ventral lobe slightly longer than the dorsal one (
<figureCitation id="130A2A22F5120930FEAAFF30FEFDCD69" box="[300,362,247,273]" captionStart="FIG" captionStartId="8.[132,143,1381,1399]" captionTargetBox="[132,1455,215,1322]" captionTargetId="figure-353@8.[132,1455,214,1339]" captionTargetPageId="8" captionText="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="9" pageNumber="1300">Fig. 2</figureCitation>
).
</paragraph>
<paragraph id="8B8E36A7F5120930FF02FED0FD45CF48" blockId="9.[131,775,215,816]" pageId="9" pageNumber="1300">
The fin “rays” (actually cartilaginous radials, see
<bibRefCitation id="EFA04B56F5120930FF02FEF0FE01CD2A" author="MARINELLI W. &amp; STRENGER A." box="[132,406,311,338]" pageId="9" pageNumber="1300" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
;
<bibRefCitation id="EFA04B56F5120930FE24FEF0FDB3CD29" author="JANVIER P." box="[418,548,311,337]" pageId="9" pageNumber="1300" pagination="1045 - 1056" refId="ref12202" refString="JANVIER P. 2008. - Early jawless vertebrates and cyclostome origins. Zoological Science 25: 1045 - 1056. https: // doi. org / 10.2108 / zsj. 25.1045" type="journal article" year="2008">
<date id="FF8F1067F5120930FE24FEF0FDB3CD29" box="[418,548,311,337]" pageId="9" pageNumber="1300" value="2008-01">Janvier 2008</date>
</bibRefCitation>
;
<bibRefCitation id="EFA04B56F5120930FDB6FEF0FC92CD29" author="MIYASHITA T. &amp; COATES M. I. &amp; LARSON P. L. &amp; MANNING P. L." box="[560,773,311,337]" pageId="9" pageNumber="1300" pagination="2146 - 2151" refId="ref12792" refString="MIYASHITA T., COATES M. I., LARSON P. L. &amp; MANNING P. L. 2019. - Hagfish from the Cretaceous Tethys Sea and a reconciliation of the morphological-molecular conflict in early vertebrate phylogeny. Proceedings of the National Academy of Sciences 116: 2146 - 2151. https: // doi. org / 10.1073 / pnas. 1814794116" type="journal article" year="2019">
Miyashita
<emphasis id="B945EAB5F5120930FD1AFEFFFD5BCD29" box="[668,716,311,337]" italics="true" pageId="9" pageNumber="1300">et al.</emphasis>
2019
</bibRefCitation>
for interpretation for lampreys and other jawless vertebrates) are easily observable and closely arranged, with a density of about two rays per millimeter, which is more closely arranged than at least in the anal fin of a female
<taxonomicName id="4C314D24F5120930FDB6FE70FEA5CD89" authority="Linnaeus, 1758" authorityName="Linnaeus" authorityYear="1758" class="Cephalaspidomorphi" family="Petromyzontidae" genus="Petromyzon" kingdom="Animalia" order="Petromyzontiformes" pageId="9" pageNumber="1300" phylum="Chordata" rank="species" species="marinus">
<emphasis id="B945EAB5F5120930FDB6FE70FC90CDA8" box="[560,775,439,464]" italics="true" pageId="9" pageNumber="1300">Petromyzon marinus</emphasis>
Linnaeus, 1758
</taxonomicName>
(
<quantity id="4CC99B42F5120930FEC3FE11FE0FCD89" box="[325,408,470,497]" metricMagnitude="-2" metricUnit="m" metricValue="3.1" pageId="9" pageNumber="1300" unit="mm" value="31.0">31 mm</quantity>
in length supported by 30 rays) (
<bibRefCitation id="EFA04B56F5120930FF08FE31FEAFCE68" author="VLADYKOV V. D." box="[142,312,502,528]" pageId="9" pageNumber="1300" pagination="221 - 224" refId="ref13596" refString="VLADYKOV V. D. 1973. - A female sea lamprey (Petromyzon marinus) with a true anal fin, and the question of the presence of an anal fin in the Petromyzontidae. Canadian Journal of Zoology 51: 221 - 224. https: // doi. org / 10.1139 / z 73 - 032" type="journal article" year="1973">Vladykov 1973</bibRefCitation>
). There is a continuous dark band in the ventral part of the anterior and “posterior dorsal” fins (
<figureCitation id="130A2A22F5120930FD44FDD1FC97CE48" box="[706,768,534,560]" captionStart="FIG" captionStartId="8.[132,143,1381,1399]" captionTargetBox="[132,1455,215,1322]" captionTargetId="figure-353@8.[132,1455,214,1339]" captionTargetPageId="8" captionText="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="9" pageNumber="1300">Figs 2</figureCitation>
;
<figureCitation id="130A2A22F5120930FF02FDF1FF5DCE29" box="[132,202,566,593]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="9" pageNumber="1300">3C, D</figureCitation>
), possibly reflecting the imprints of the radial muscles (
<bibRefCitation id="EFA04B56F5120930FF08FD91FEFECE08" author="SANSOM R. S. &amp; GABBOOTT S. A. &amp; PURNELL M. A." box="[142,361,598,624]" pageId="9" pageNumber="1300" pagination="1150 - 1157" refId="ref13479" refString="SANSOM R. S., GABBOOTT S. A. &amp; PURNELL M. A. 2010. - Decay of vertebrate characters in hagfish and lamprey (Cyclostomata) and the implications for the vertebrate fossil record. Proceedings of the Royal Society B 278: 1150 - 1157. https: // doi. org / 10.1098 / rspb. 2010.1641" type="journal article" year="2010">
Sansom
<emphasis id="B945EAB5F5120930FF68FD90FEB2CE08" box="[238,293,598,624]" italics="true" pageId="9" pageNumber="1300">et al.</emphasis>
2010
</bibRefCitation>
: fig. 2a) and/or the adipose stratum (
<bibRefCitation id="EFA04B56F5120930FF0BFDB1FE24CEE9" author="MARINELLI W. &amp; STRENGER A." box="[141,435,630,657]" pageId="9" pageNumber="1300" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
: (figs 43, 44, 49). It is noticed that in IVPP
<accessionNumber id="9462AB44F5120930FE96FD51FEF9CEC8" box="[272,366,661,688]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15027" pageId="9" pageNumber="1300" type="EnaNcbi">V 15027</accessionNumber>
A, there is a dorsal swelling of the body at the anterior base of the “posterior dorsal fin”, which is not seen in other specimens (
<figureCitation id="130A2A22F5120930FE14FD12FE72CE88" box="[402,485,725,752]" captionStart="FIG" captionStartId="8.[132,143,1381,1399]" captionTargetBox="[132,1455,215,1322]" captionTargetId="figure-353@8.[132,1455,214,1339]" captionTargetPageId="8" captionText="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="9" pageNumber="1300">Fig. 2A</figureCitation>
). This fin is not completely preserved in the
<typeStatus id="548A8805F5120930FEB3FD32FE02CF77" box="[309,405,757,783]" pageId="9" pageNumber="1300" type="holotype">holotype</typeStatus>
and referred to as emerging above the posterior portion of the body (
<bibRefCitation id="EFA04B56F5120930FE78FCD2FD56CF57" author="CHANG M. - M. &amp; ZHANG J. Y. &amp; MIAO D. S." box="[510,705,789,815]" pageId="9" pageNumber="1300" pagination="972 - 974" refId="ref11511" refString="CHANG M. - M., ZHANG J. Y. &amp; MIAO D. S. 2006. - A lamprey from the Cretaceous Jehol biota of China. Nature 441: 972 - 974. https: // doi. org / 10.1038 / nature 04730" type="journal article" year="2006">
Chang
<emphasis id="B945EAB5F5120930FDC8FCD1FD15CF57" box="[590,642,789,815]" italics="true" pageId="9" pageNumber="1300">et al.</emphasis>
2006
</bibRefCitation>
).
</paragraph>
<paragraph id="8B8E36A7F5120930FF02FC92FE8ECF17" blockId="9.[132,281,853,879]" box="[132,281,853,879]" pageId="9" pageNumber="1300">
<heading id="D0C681CBF5120930FF02FC92FE8ECF17" box="[132,281,853,879]" fontSize="11" level="2" pageId="9" pageNumber="1300" reason="8">
<emphasis id="B945EAB5F5120930FF02FC92FE8ECF17" box="[132,281,853,879]" italics="true" pageId="9" pageNumber="1300">Anal fin (fold)</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F5120930FF02FCB2FE54C857" blockId="9.[131,777,885,1071]" pageId="9" pageNumber="1300">
The anal fin (fold) is present just behind the anus (cloaca), which is best preserved in IVPP
<accessionNumber id="9462AB44F5120930FE71FC52FDCDCFC8" box="[503,602,917,944]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V15449" pageId="9" pageNumber="1300" type="EnaNcbi">V 15449</accessionNumber>
(
<figureCitation id="130A2A22F5120930FDEDFC52FD53CFD7" box="[619,708,917,943]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="9" pageNumber="1300">Fig. 3G</figureCitation>
). It is shallow and elongate but separate from the ventral lobe of the caudal fin. It is more a skin fold than a “true” fin because no traces are detected as the supporting rays for this fin as in living form (
<bibRefCitation id="EFA04B56F5120930FE8BFBD3FE24C856" author="VLADYKOV V. D." box="[269,435,1044,1070]" pageId="9" pageNumber="1300" pagination="221 - 224" refId="ref13596" refString="VLADYKOV V. D. 1973. - A female sea lamprey (Petromyzon marinus) with a true anal fin, and the question of the presence of an anal fin in the Petromyzontidae. Canadian Journal of Zoology 51: 221 - 224. https: // doi. org / 10.1139 / z 73 - 032" type="journal article" year="1973">Vladykov 1973</bibRefCitation>
).
</paragraph>
<paragraph id="8B8E36A7F5120930FF02FB93FEA5C816" blockId="9.[132,306,1108,1134]" box="[132,306,1108,1134]" pageId="9" pageNumber="1300">
<heading id="D0C681CBF5120930FF02FB93FEA5C816" box="[132,306,1108,1134]" fontSize="11" level="2" pageId="9" pageNumber="1300" reason="8">
<emphasis id="B945EAB5F5120930FF02FB93FEA5C816" box="[132,306,1108,1134]" italics="true" pageId="9" pageNumber="1300">Preanal skin fold</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F5120930FF02FBB3FE1ECB54" blockId="9.[130,777,1140,1836]" pageId="9" pageNumber="1300">
An unexpected finding is the long preanal skin fold that emerges immediately before the anus (cloaca) and extends on the ventral midline (
<figureCitation id="130A2A22F5120930FE09FB73FD9EC8B6" box="[399,521,1204,1230]" captionStart="FIG" captionStartId="8.[132,143,1381,1399]" captionTargetBox="[132,1455,215,1322]" captionTargetId="figure-353@8.[132,1455,214,1339]" captionTargetPageId="8" captionText="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="9" pageNumber="1300">Figs 2A, C</figureCitation>
;
<figureCitation id="130A2A22F5120930FD9FFB73FDA9C8B6" box="[537,574,1204,1230]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="9" pageNumber="1300">3H</figureCitation>
). This structure is common in fossil lampreys from different localities of Jehol Biota. It reaches the level of the front end of the branchial apparatus (i.e., beyond the anterior termination of the anterior dorsal fin), at which point it becomes very shallow. This fold can be seen in IVPP
<accessionNumber id="9462AB44F5120930FEE4FA93FE54C915" box="[354,451,1363,1390]" httpUri="https://www.ebi.ac.uk/ena/browser/api/embl/V14981" pageId="9" pageNumber="1300" type="EnaNcbi">V 14981</accessionNumber>
B, 15027 and 15448, where it is much lighter in color than and clearly distinct in texture from the impressions of the trunk myomeres. Moreover, it is separated from the trunk myomere imprints by a clear black line delineating the ventral midline (
<figureCitation id="130A2A22F5120930FE7AFA14FDDAC995" box="[508,589,1491,1517]" captionStart="FIG" captionStartId="8.[132,143,1381,1399]" captionTargetBox="[132,1455,215,1322]" captionTargetId="figure-353@8.[132,1455,214,1339]" captionTargetPageId="8" captionText="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="9" pageNumber="1300">Figs 2C</figureCitation>
;
<figureCitation id="130A2A22F5120930FDD1FA14FDE9C995" box="[599,638,1491,1517]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="9" pageNumber="1300">3H</figureCitation>
). In contrast, there is no additional structure below the trunk myomeres in living lampreys as evidenced by the transverse section of the body (
<bibRefCitation id="EFA04B56F5120930FF4AF9F5FE64CA35" author="MARINELLI W. &amp; STRENGER A." box="[204,499,1586,1613]" pageId="9" pageNumber="1300" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
: figs 42-44). In fossils at hand this fold is occasionally preserved in the way of wrinkling, suggestive a thin and soft nature, distinct from the stiff and straight ventral edge of the body. Additionally, its distal line is always clear rather than the obscure outline in decayed carcass (
<bibRefCitation id="EFA04B56F5120930FF5CF915FE08CA94" author="SANSOM R. S. &amp; GABBOOTT S. A. &amp; PURNELL M. A." box="[218,415,1746,1772]" pageId="9" pageNumber="1300" pagination="457 - 474" refId="ref13543" refString="SANSOM R. S., GABBOOTT S. A. &amp; PURNELL M. A. 2013. - Atlas of vertebrate decay: a visual and taphonomic guide to fossil interpretation. Palaeontology 56: 457 - 474. https: // doi. org / 10.1111 / pala. 12037" type="journal article" year="2013">
Sansom
<emphasis id="B945EAB5F5120930FEB5F914FEF3CA94" box="[307,356,1746,1772]" italics="true" pageId="9" pageNumber="1300">et al.</emphasis>
2013
</bibRefCitation>
). According to current observable information, this fold is most likely median in position and lacks supporting radials.
</paragraph>
<paragraph id="8B8E36A7F5120930FF02F895FF7ECB13" blockId="9.[132,233,1874,1899]" box="[132,233,1874,1899]" pageId="9" pageNumber="1300">
<heading id="D0C681CBF5120930FF02F895FF7ECB13" box="[132,233,1874,1899]" fontSize="11" level="2" pageId="9" pageNumber="1300" reason="8">
<emphasis id="B945EAB5F5120930FF02F895FF7ECB13" box="[132,233,1874,1899]" italics="true" pageId="9" pageNumber="1300">Myomeres</emphasis>
</heading>
</paragraph>
<paragraph id="8B8E36A7F5120930FF02F8B6FC90CB94" blockId="9.[131,775,1905,2028]" pageId="9" pageNumber="1300">
The number of the trunk myomeres are counted in the range of 70-80. The trunk myomeres show a zig-zag profile (
<figureCitation id="130A2A22F5120930FD47F856FC97CBD3" box="[705,768,1937,1963]" captionStart="FIG" captionStartId="8.[132,143,1381,1399]" captionTargetBox="[132,1455,215,1322]" captionTargetId="figure-353@8.[132,1455,214,1339]" captionTargetPageId="8" captionText="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="9" pageNumber="1300">Figs 2</figureCitation>
;
<figureCitation id="130A2A22F5120930FF02F876FF3ECBB4" box="[132,169,1969,1996]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="9" pageNumber="1300">3H</figureCitation>
) with the ventral section lacking the posteriorly-pointing apex of living forms (
<bibRefCitation id="EFA04B56F5120930FEF1F816FDD8CB93" author="SANSOM R. S. &amp; GABBOOTT S. A. &amp; PURNELL M. A." box="[375,591,2001,2027]" pageId="9" pageNumber="1300" pagination="1150 - 1157" refId="ref13479" refString="SANSOM R. S., GABBOOTT S. A. &amp; PURNELL M. A. 2010. - Decay of vertebrate characters in hagfish and lamprey (Cyclostomata) and the implications for the vertebrate fossil record. Proceedings of the Royal Society B 278: 1150 - 1157. https: // doi. org / 10.1098 / rspb. 2010.1641" type="journal article" year="2010">
Sansom
<emphasis id="B945EAB5F5120930FE50F815FD9ACB93" box="[470,525,2001,2027]" italics="true" pageId="9" pageNumber="1300">et al.</emphasis>
2010
</bibRefCitation>
;
<bibRefCitation id="EFA04B56F5120930FDD9F816FD61CB93" author="RENAUD C. B." box="[607,758,2001,2027]" pageId="9" pageNumber="1300" refId="ref13356" refString="RENAUD C. B. 2011. - Lampreys of the World. An annotated and illustrated catalogue of lamprey species known to date. FAO Species Catalogue for Fishery Purposes no. 5. Food and Agriculture Organization of the United Nations, Rome: 109 p." type="book" year="2011">Renaud 2011</bibRefCitation>
),
</paragraph>
<paragraph id="8B8E36A7F5120930FCABFF10FAFBCD0A" blockId="9.[811,1457,215,370]" pageId="9" pageNumber="1300">
whereas those caudal myomeres show a typical W-shaped profile, with the median apex pointing anteriorly (
<figureCitation id="130A2A22F5120930FAE3FF30FA3FCD69" box="[1381,1448,247,273]" captionStart="FIG" captionStartId="8.[132,143,1381,1399]" captionTargetBox="[132,1455,215,1322]" captionTargetId="figure-353@8.[132,1455,214,1339]" captionTargetPageId="8" captionText="FIG. 2. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, new adult individuals and morphological restoration:A, photograph of IVPP V 15027; B, photograph of IVPP V 15449; C, photograph of IVPP V 14981B; D, restoration of the general appearance of Mesomyzon, dotted circle behind the eyes representing the otic capsule. Abbreviations: adf, anterior dorsal fin; bp, branchial pouches; cf, caudal fin; cl, cloaca; e, eye(s); egp, external gill pores; od, oral disc; pdf, posterior dorsal fin. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764681" httpUri="https://zenodo.org/record/5764681/files/figure.png" pageId="9" pageNumber="1300">Figs 2</figureCitation>
;
<figureCitation id="130A2A22F5120930FCABFED0FCC4CD49" box="[813,851,279,305]" captionStart="FIG" captionStartId="10.[132,143,1619,1637]" captionTargetBox="[132,1456,243,1562]" captionTargetId="figure-116@10.[132,1458,242,1565]" captionTargetPageId="10" captionText="FIG. 3. — Mesomyzon mengae Chang, Zhang &amp; Miao, 2006, head, branchial region, and fins. Photographs of: A, IVPP V 15027A; B, IVPP V 15035A; photograph (C) and line drawing (D) of IVPP V 15449; photograph (E) and line drawing (F) of IVPP V 15450.3; G, photograph of the tail of IVPP V 15449, the arrow points to the anal fold; H, close-up of middle trunk of IVPP V 14981B. Abbreviations: ac, annular cartilage; adc, anterior dorsal cartilage; adf, anterior dorsal fin; ao, anterior pillar of subocular cartilage; ap, apicalis and the laminae it carries;atr, naso-hypophysial atrium; ba, imprints of brain;bb, branchial basket; cot, circumoral teeth; da, dorsal aorta; dt, detritus in intestine; eh, extra hyal arch; m, mouth; gp1, gp7, 1st and 7th gill pouch; il, infraoral lamina; lv, liver; no, external narial opening; nhp, hypophysial pouch; gl, gill filaments;gf(l, r), gill filaments of left and right gills; gp, infillings of gular pouch; lo, olfactory organ; my, myomeres; nlp, posterior lateral nerve; ns, nasal sac; oc, otic capsule; oca, oral cavity; op, oral papillae; of, oral fimbriae; p, piston cartilage; paf, preanal skin fold; pc, pericardial cartilage; pdc, posterior dorsal cartilage; sl, supraoral lamina; st, styliform; tel, telencephalon; vs, velar skeleton; I, olfactory nerve or tract; V1, ophthalmic ramus of trigeminal nerve; VII. uc, buccal ramus of facial nerve; VII.rec, recurrent ramus of facial nerve surrounding labyrinth;IX, glossopharyngeus nerve; X, vagus nerve. See Figure 2 for other abbreviations. Anterior facing left in all figures. Scale bars: 10 mm." figureDoi="http://doi.org/10.5281/zenodo.5764683" httpUri="https://zenodo.org/record/5764683/files/figure.png" pageId="9" pageNumber="1300">3G</figureCitation>
). The impressions the trunk muscular fibers are clearly observable and arranged in paralleling longitudinal direction as in living forms (
<bibRefCitation id="EFA04B56F5120930FC71FE90FA8FCD0A" author="MARINELLI W. &amp; STRENGER A." box="[1015,1304,343,370]" pageId="9" pageNumber="1300" refId="ref12733" refString="MARINELLI W. &amp; STRENGER A. 1954. - Vergleichende Anatomie und Morphologie derWirbeltiere. I Lieferung. Petromyzon marinus (L). Deuticke, Wien." type="book" year="1954">Marinelli &amp; Strenger 1954</bibRefCitation>
: fig. 6).
</paragraph>
</subSubSection>
</treatment>
</document>
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