292 lines
66 KiB
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292 lines
66 KiB
XML
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<mods:title id="1B6E63A1757E7515807AC5BDB8497A55">Morphology and histology of dorsal spines of the xenacanthid shark Orthacanthus platypternus from the Lower Permian of Texas, USA: Palaeobiological and palaeoenvironmental implications</mods:title>
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<mods:namePart id="64C110E975E3891B157232180BFA8D5B">Beck, Kimberly G.</mods:namePart>
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<mods:namePart id="3C0AC470F18F82ED84D3DE09D08F3385">Soler-Gijón, Rodrigo</mods:namePart>
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<mods:namePart id="F4F6708DBA0E50003C17A0B8BA57AC1C">Carlucci, Jesse R.</mods:namePart>
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<mods:namePart id="6974CE1DC777D61C4E7DEE0D7D709C00">Willis, Ray E.</mods:namePart>
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<mods:title id="99967BB5A0190629F1026F8FBE9C4312">Acta Palaeontologica Polonica</mods:title>
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<mods:date id="8704931C4EBC0F71D64FE3772F9C160C">2016</mods:date>
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<treatment id="039A87B549122D22EA19FC30FA6514C0" LSID="urn:lsid:plazi:treatment:039A87B549122D22EA19FC30FA6514C0" httpUri="http://treatment.plazi.org/id/039A87B549122D22EA19FC30FA6514C0" lastPageId="8" lastPageNumber="105" pageId="5" pageNumber="102">
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<subSubSection id="C329652849122D2FEA19FC30FDFA15AA" box="[98,618,985,1014]" pageId="5" pageNumber="102" type="nomenclature">
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<paragraph id="8B8C36A349122D2FEA19FC30FDFA15AA" blockId="5.[98,618,985,1014]" box="[98,618,985,1014]" pageId="5" pageNumber="102">
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<heading id="D0C481CF49122D2FEA19FC30FDFA15AA" box="[98,618,985,1014]" fontSize="12" level="2" pageId="5" pageNumber="102" reason="2">
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<taxonomicName id="4C334D2049122D2FEA19FC30FDFA15AA" authority="(Cope, 1884)" baseAuthorityName="Cope" baseAuthorityYear="1884" box="[98,618,985,1014]" class="Chondrichthyes" family="Xenacanthidae" genus="Orthacanthus" kingdom="Animalia" order="Xenacanthiformes" pageId="5" pageNumber="102" phylum="Chordata" rank="species" species="platypternus">
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<emphasis id="B947EAB149122D2FEA19FC30FE2A15AA" box="[98,442,986,1014]" italics="true" pageId="5" pageNumber="102">Orthacanthus platypternus</emphasis>
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(
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<bibRefCitation id="EFA24B5249122D2FEBB0FC33FDF215AA" author="Cope, E. D." box="[459,610,985,1014]" pageId="5" pageNumber="102" pagination="572 - 590" refId="ref15299" refString="Cope, E. D. 1884. On the structure of the skull in the elasmobranch genus Didymodus. Proceedings of the American Philosophical Society 21: 572 - 590." type="journal article" year="1884">Cope, 1884</bibRefCitation>
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)
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</taxonomicName>
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</heading>
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</paragraph>
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</subSubSection>
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<subSubSection id="C329652849122D22EA19FBEFFA6514C0" lastPageId="8" lastPageNumber="105" pageId="5" pageNumber="102" type="description">
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<paragraph id="8B8C36A349122D2FEA19FBEFFE901247" blockId="5.[98,256,1029,1051]" box="[98,256,1029,1051]" pageId="5" pageNumber="102">
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<figureCitation id="13082A2649122D2FEA19FBEFFF2B1247" box="[98,187,1029,1051]" captionStart-0="Fig" captionStart-1="Fig" captionStart-2="Fig" captionStart-3="Fig" captionStart-4="Fig" captionStartId-0="4.[151,184,1739,1761]" captionStartId-1="6.[151,184,1654,1674]" captionStartId-2="7.[98,131,1066,1088]" captionStartId-3="8.[151,184,1485,1507]" captionStartId-4="9.[98,131,1319,1341]" captionTargetBox-0="[174,1513,160,1721]" captionTargetBox-1="[152,1533,163,1628]" captionTargetBox-2="[126,1452,161,1043]" captionTargetBox-3="[160,810,170,1462]" captionTargetBox-4="[120,1458,161,1295]" captionTargetId-1="figure-187@6.[152,1515,184,1288]" captionTargetId-2="figure-434@7.[241,1453,161,1017]" captionTargetId-3="figure-550@8.[153,823,164,1453]" captionTargetId-4="figure-292@9.[121,1458,160,1269]" captionTargetPageId-0="4" captionTargetPageId-1="6" captionTargetPageId-2="7" captionTargetPageId-3="8" captionTargetPageId-4="9" captionText-0="Fig.3. External morphology of dorsal spines of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA. A. HMNS-T1, juvenile,lateral view.B. SMU 68799,juvenile, posterior view.C. SMU 68800, juvenile, posterior (C1) and postero-lateral (C2) views.D. SMU 68801, adult, denticulated, postero-lateral view (D1) and non-denticulated, posterior view (D2) regions. Numbers 1 to 17 point to the positions of the denticles along the posterior sides of the spines. Numbers 1’ to 17’ correspond to the right row of denticles.Grey areas in B–D2 represent sedimentary matrix. Scale bars 5 mm." captionText-1="Fig. 4. Serial longitudinal sections of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-T2, where A represents the most proximal section and E is the most distal. Samples C–E include the denticulate region. Photos of the sections (A1–E1), interpretative drawings (A2–E2). Scale bars 1 mm." captionText-2="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." captionText-3="Fig. 6. Cross-sections of dorsal spines (non-denticulated region) of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA. Comparison between the smallest, specimen HMNS-T1 (A), and the largest Orthacanthus dorsal spine sampled, specimen HMNS-J1 (B). Posterior sides of the spines are pointing to the top of the figure." captionText-4="Fig. 7. Cross-section of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J7 non-denticulated region) showing color-banding in centrifugal trabecular dentine and growth lines in lamellar dentine. A. General view (posterior side of spine towards the top of the figure). B, C. Details of periphery showing pairs of growth lines (marked by arrows) in the centrifugal lamellar dentine. D. Detail of interglobular spaces within the centripetal lamellar dentine (arrows denote interglobular spaces)." figureDoi-0="http://doi.org/10.5281/zenodo.10980752" figureDoi-1="http://doi.org/10.5281/zenodo.10980754" figureDoi-2="http://doi.org/10.5281/zenodo.10980756" figureDoi-3="http://doi.org/10.5281/zenodo.10980758" figureDoi-4="http://doi.org/10.5281/zenodo.10980760" httpUri-0="https://zenodo.org/record/10980752/files/figure.png" httpUri-1="https://zenodo.org/record/10980754/files/figure.png" httpUri-2="https://zenodo.org/record/10980756/files/figure.png" httpUri-3="https://zenodo.org/record/10980758/files/figure.png" httpUri-4="https://zenodo.org/record/10980760/files/figure.png" pageId="5" pageNumber="102">Figs. 3–7</figureCitation>
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,
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<figureCitation id="13082A2649122D2FEABEFBECFF741247" box="[197,228,1030,1051]" captionStart="Fig" captionStartId="10.[151,184,993,1015]" captionTargetBox="[163,1526,165,966]" captionTargetId="figure-558@10.[152,1532,205,914]" captionTargetPageId="10" captionText="Fig.8. A.Reconstruction ofthe dorsal spine(mainly the denticulated region) of Orthacanthus platypternus, basedon specimens HMNS-T1 and HMNS-T2. B, C. Reconstructions of the dorsal spine of Orthacanthus meridionalis (modified from Soler-Gijón 1999: fig.10); PU-XE76 (B) PU-XE19 (C). Note that distal denticles belong to the first spine (juvenile).The intersection of the first major growth line and the denticulated border of the spine indicate the proximal end of the denticulated region of the first spine; the following “spines” exhibit the distal denticles and those corresponding to each new growth stage." figureDoi="http://doi.org/10.5281/zenodo.10980762" httpUri="https://zenodo.org/record/10980762/files/figure.png" pageId="5" pageNumber="102">8A</figureCitation>
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,
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<figureCitation id="13082A2649122D2FEA95FBECFF6B1247" box="[238,251,1030,1051]" captionStart="Fig" captionStartId="11.[98,131,1655,1677]" captionTargetBox="[213,1365,161,1632]" captionTargetPageId="11" captionText="Fig. 9. Bivariate plots of relationship between width and height in cross sections of Orthacanthus dorsal spines. A. Orthacanthus platypternus (Lower Permian, Craddock Bone Bed, Texas, USA). B. Comparison of O. platypternus with O. meridionalis (Upper Carboniferous, Puertollano, Spain) and Orthacanthus sp. (Upper Carboniferous, Robinson, Kansas, USA). Note the linear regression (y = 0.91x + 0.15; n = 65, r2 = 0.98) calculated by Donelan and Johnson (1997) for the isolated dorsal spines of O. platypternus. The maximum and minimal values are also included here for a comparative reference; values of the rest of the specimens are not included for clarity. Grey shaded areas indicate approximate intervals of the three size clusters corresponding to juveniles and adults according the biometric analysis by Donelan and Johnson (size intervals are based on unpublished data presented in a poster at 57th Annual Meeting of the Society of Vertebrate Paleontology, Chicago, October 1997). Note the ontogenetic trajectories of several individuals of O. platypternus (HMNS-T2 and HMNS-J3), O. meridionalis (PU-XE19, 20, 74 and 76) and Orthacanthus sp. (KUVP-72324) showing stages SP1–n spine proper). Data from O. meridionalis and Orthacanthus sp. after Soler-Gijón (1999: table 1 and figs. 4–8). Vertical grey arrows point to the position in the linear regression for SMU specimens according the maximum width values at the proximal end of denticulated regions: 3.5 mm (SMU 68799), 4.5 mm (SMU 68800) and 8.4 mm (SMU 68801). Abbreviations: SP1–5, spines 1–5; SpPr, spine proper." figureDoi="http://doi.org/10.5281/zenodo.10980764" httpUri="https://zenodo.org/record/10980764/files/figure.png" pageId="5" pageNumber="102">9</figureCitation>
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.
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</paragraph>
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<paragraph id="8B8C36A349122D2FEA19FBC4FEA91294" blockId="5.[98,770,1068,1224]" pageId="5" pageNumber="102">
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<emphasis id="B947EAB149122D2FEA19FBC4FEB9121B" box="[98,297,1070,1095]" italics="true" pageId="5" pageNumber="102">Referred material</emphasis>
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.—15 isolated dorsal spines (HMNS-T1–2, HMNS-J1–10,
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<collectionCode id="ED22AE6649122D2FEB6DFBA7FEC4123B" box="[278,340,1101,1127]" country="South Korea" httpUri="http://grbio.org/cool/sv00-20xv" name="Sangmiung University" pageId="5" pageNumber="102">SMU</collectionCode>
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68799–68801) from the Craddock Bone Bed (northern Baylor County,
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<collectingRegion id="49F7F84149122D2FE860FB84FDCF12D4" box="[539,607,1134,1160]" country="United States of America" name="Texas" pageId="5" pageNumber="102">Texas</collectingRegion>
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,
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<collectingCountry id="F324763349122D2FE80BFB87FD3A12DB" box="[624,682,1133,1159]" name="United States of America" pageId="5" pageNumber="102">USA</collectingCountry>
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), lower Clear Fork Formation, Early Permian (Leonardian age; see
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<bibRefCitation id="EFA24B5249122D2FEA19FB44FEBD1294" author="Nelson, W. J. & Hook, R. W. & Chaney, D. S." box="[98,301,1198,1224]" pageId="5" pageNumber="102" pagination="286 - 311" refId="ref17381" refString="Nelson, W. J., Hook, R. W., and Chaney, D. S. 2013. Lithostratigraphy of the Lower Permian (Leonardian) Clear Fork Formation of North-Central Texas. New Mexico Museum of Natural History and Science Bulletin 60: 286 - 311." type="journal article" year="2013">Nelson et al. 2013</bibRefCitation>
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).
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</paragraph>
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<paragraph id="8B8C36A349122D2FEA19FB0BFF7D12A7" blockId="5.[98,237,1249,1275]" box="[98,237,1249,1275]" pageId="5" pageNumber="102">
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<emphasis id="B947EAB149122D2FEA19FB0BFF7D12A7" box="[98,237,1249,1275]" italics="true" pageId="5" pageNumber="102">Description</emphasis>
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</paragraph>
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<paragraph id="8B8C36A349122D2FEA19FAE0FC93113B" blockId="5.[98,771,1289,1960]" pageId="5" pageNumber="102">
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<emphasis id="B947EAB149122D2FEA19FAE0FEDA137F" box="[98,330,1290,1315]" italics="true" pageId="5" pageNumber="102">General morphology</emphasis>
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.—The external morphology of a dorsal spine of
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<taxonomicName id="4C334D2049122D2FEAB3FAC0FE6B131F" baseAuthorityName="Cope" baseAuthorityYear="1884" box="[200,507,1322,1347]" class="Liliopsida" family="Poaceae" genus="Orthacanthus" kingdom="Plantae" order="Poales" pageId="5" pageNumber="102" phylum="Tracheophyta" rank="species" species="platypternus">
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<emphasis id="B947EAB149122D2FEAB3FAC0FE6B131F" box="[200,507,1322,1347]" italics="true" pageId="5" pageNumber="102">Orthacanthus platypternus</emphasis>
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</taxonomicName>
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is well represented by the specimen
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<collectionCode id="ED22AE6649122D2FEA87FAA3FEA9133F" box="[252,313,1353,1379]" country="South Korea" httpUri="http://grbio.org/cool/sv00-20xv" name="Sangmiung University" pageId="5" pageNumber="102">SMU</collectionCode>
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68801 (
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<figureCitation id="13082A2649122D2FEBE8FAA3FE79133F" box="[403,489,1353,1379]" captionStart="Fig" captionStartId="4.[151,184,1739,1761]" captionTargetBox="[174,1513,160,1721]" captionTargetPageId="4" captionText="Fig.3. External morphology of dorsal spines of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA. A. HMNS-T1, juvenile,lateral view.B. SMU 68799,juvenile, posterior view.C. SMU 68800, juvenile, posterior (C1) and postero-lateral (C2) views.D. SMU 68801, adult, denticulated, postero-lateral view (D1) and non-denticulated, posterior view (D2) regions. Numbers 1 to 17 point to the positions of the denticles along the posterior sides of the spines. Numbers 1’ to 17’ correspond to the right row of denticles.Grey areas in B–D2 represent sedimentary matrix. Scale bars 5 mm." figureDoi="http://doi.org/10.5281/zenodo.10980752" httpUri="https://zenodo.org/record/10980752/files/figure.png" pageId="5" pageNumber="102">Fig. 3D</figureCitation>
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),
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<quantity id="4CCB9B4649122D2FEB86FAA3FDC61338" box="[509,598,1353,1380]" metricMagnitude="-1" metricUnit="m" metricValue="1.14" pageId="5" pageNumber="102" unit="mm" value="114.0">114 mm</quantity>
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long, and lacking the most distal region. Two posterior rows of denticles covered about
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<quantity id="4CCB9B4649122D2FEB70FA60FECD13F8" box="[267,349,1418,1444]" metricMagnitude="-2" metricUnit="m" metricValue="4.8" pageId="5" pageNumber="102" unit="mm" value="48.0">48 mm</quantity>
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of the complete length of the spine, indicating that the denticulation could be extended for the distal half of the complete spine. The cross-section was oval near the opening of the pulp cavity but became circular to subtriangular in the distal part of the non-denticulated region and circular in the denticulated region. The spine was
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<quantity id="4CCB9B4649122D2FEA19F9A1FF28103A" box="[98,184,1611,1638]" metricMagnitude="-3" metricUnit="m" metricValue="8.4" pageId="5" pageNumber="102" unit="mm" value="8.4">8.4 mm</quantity>
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wide at the proximal end of the denticulated region and reached a maximum width of
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<quantity id="4CCB9B4649122D2FEB90F981FDD110DA" box="[491,577,1643,1670]" metricMagnitude="-3" metricUnit="m" metricValue="9.4" pageId="5" pageNumber="102" unit="mm" value="9.4">9.4 mm</quantity>
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proximally, near the basal opening of the pulp cavity. The robustness index maximum width to total length ratio) of the preserved spine is 1:12. The denticle sizes (base length) ranged
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<quantity id="4CCB9B4649122D2FE803F926FD6F10BA" box="[632,767,1740,1766]" metricMagnitude="-3" metricUnit="m" metricValue="2.0" metricValueMax="2.3" metricValueMin="1.7" pageId="5" pageNumber="102" unit="mm" value="2.0" valueMax="2.3" valueMin="1.7">1.7–2.3 mm</quantity>
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. A density of denticulation of 0.40 denticles/mm remained uniform through the spine
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<collectionCode id="ED22AE6649122D2FEBDEF8E7FE72117B" box="[421,482,1805,1831]" country="South Korea" httpUri="http://grbio.org/cool/sv00-20xv" name="Sangmiung University" pageId="5" pageNumber="102">SMU</collectionCode>
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68801 and in the much smaller fragmentary specimens
|
||
<collectionCode id="ED22AE6649122D2FEBB0F8C7FD98111B" box="[459,520,1837,1863]" country="South Korea" httpUri="http://grbio.org/cool/sv00-20xv" name="Sangmiung University" pageId="5" pageNumber="102">SMU</collectionCode>
|
||
68799 and 68800 (juveniles) that showed the most proximal denticles (
|
||
<figureCitation id="13082A2649122D2FE8F8F8A7FD65113B" box="[643,757,1869,1895]" captionStart="Fig" captionStartId="4.[151,184,1739,1761]" captionTargetBox="[174,1513,160,1721]" captionTargetPageId="4" captionText="Fig.3. External morphology of dorsal spines of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA. A. HMNS-T1, juvenile,lateral view.B. SMU 68799,juvenile, posterior view.C. SMU 68800, juvenile, posterior (C1) and postero-lateral (C2) views.D. SMU 68801, adult, denticulated, postero-lateral view (D1) and non-denticulated, posterior view (D2) regions. Numbers 1 to 17 point to the positions of the denticles along the posterior sides of the spines. Numbers 1’ to 17’ correspond to the right row of denticles.Grey areas in B–D2 represent sedimentary matrix. Scale bars 5 mm." figureDoi="http://doi.org/10.5281/zenodo.10980752" httpUri="https://zenodo.org/record/10980752/files/figure.png" pageId="5" pageNumber="102">Fig. 3B, C</figureCitation>
|
||
).
|
||
</paragraph>
|
||
<paragraph id="8B8C36A349122D2FEAFCF887FA5317A6" blockId="5.[98,771,1289,1960]" lastBlockId="5.[808,1481,158,506]" pageId="5" pageNumber="102">
|
||
The most distal denticulation (
|
||
<figureCitation id="13082A2649122D2FEBA2F887FDBC11DB" box="[473,556,1901,1927]" captionStart="Fig" captionStartId="4.[151,184,1739,1761]" captionTargetBox="[174,1513,160,1721]" captionTargetPageId="4" captionText="Fig.3. External morphology of dorsal spines of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA. A. HMNS-T1, juvenile,lateral view.B. SMU 68799,juvenile, posterior view.C. SMU 68800, juvenile, posterior (C1) and postero-lateral (C2) views.D. SMU 68801, adult, denticulated, postero-lateral view (D1) and non-denticulated, posterior view (D2) regions. Numbers 1 to 17 point to the positions of the denticles along the posterior sides of the spines. Numbers 1’ to 17’ correspond to the right row of denticles.Grey areas in B–D2 represent sedimentary matrix. Scale bars 5 mm." figureDoi="http://doi.org/10.5281/zenodo.10980752" httpUri="https://zenodo.org/record/10980752/files/figure.png" pageId="5" pageNumber="102">Fig. 3A</figureCitation>
|
||
) of a juvenile spine was preserved on the smallest spine sampled (HMNS-T1). Thirteen denticles covered approximately
|
||
<quantity id="4CCB9B4649122D2FEF68FF74FAEA16E5" box="[1299,1402,158,185]" metricMagnitude="-2" metricUnit="m" metricValue="2.35" pageId="5" pageNumber="102" unit="mm" value="23.5">23.5 mm</quantity>
|
||
of the total spine fragment length (
|
||
<quantity id="4CCB9B4649122D2FEE00FF54FB441685" box="[1147,1236,190,217]" metricMagnitude="-2" metricUnit="m" metricValue="4.0" pageId="5" pageNumber="102" unit="mm" value="40.0">40 mm</quantity>
|
||
). These denticles increased in base length and denticle height proximally except for the most proximal denticle, which was approximately
|
||
<quantity id="4CCB9B4649122D2FEFC0FF15FCC41765" metricMagnitude="-3" metricUnit="m" metricValue="1.0" pageId="5" pageNumber="102" unit="mm" value="1.0">1 mm</quantity>
|
||
shorter in length than the denticle before (distal to) it. Spacing between denticles on HMNS-T1 increased proximally until the 6
|
||
<superScript id="7C469BEB49122D2FE98DFEB7FB961732" attach="left" box="[1014,1030,349,366]" fontSize="7" pageId="5" pageNumber="102">th</superScript>
|
||
denticle, after which spacing between denticles fluctuated. The denticle sizes ranged from
|
||
<quantity id="4CCB9B4649122D2FEF0FFE95FA5817C5" box="[1396,1480,383,409]" metricMagnitude="-4" metricUnit="m" metricValue="4.0" pageId="5" pageNumber="102" unit="mm" value="0.4">0.4 mm</quantity>
|
||
(first denticle, distally) to
|
||
<quantity id="4CCB9B4649122D2FEE31FE75FB1A17E5" box="[1098,1162,415,441]" metricMagnitude="-3" metricUnit="m" metricValue="2.0" pageId="5" pageNumber="102" unit="mm" value="2.0">2 mm</quantity>
|
||
(denticle 13). The density of denticulation dramatically increased from 1.1 denticles/mm in the distal part to 0.32 denticles/mm in the proximal part.
|
||
</paragraph>
|
||
<paragraph id="8B8C36A349122D2FE953FDE1FB7D15F9" blockId="5.[808,1482,522,1960]" pageId="5" pageNumber="102">
|
||
<emphasis id="B947EAB149122D2FE953FDE1FC041478" box="[808,916,523,548]" italics="true" pageId="5" pageNumber="102">Histology</emphasis>
|
||
.—The general histology of spines thin-sectioned is shown in serial longitudinal sections (
|
||
<figureCitation id="13082A2649122D2FEF7AFDC0FAD61418" box="[1281,1350,554,580]" captionStart="Fig" captionStartId="6.[151,184,1654,1674]" captionTargetBox="[152,1533,163,1628]" captionTargetId="figure-187@6.[152,1515,184,1288]" captionTargetPageId="6" captionText="Fig. 4. Serial longitudinal sections of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-T2, where A represents the most proximal section and E is the most distal. Samples C–E include the denticulate region. Photos of the sections (A1–E1), interpretative drawings (A2–E2). Scale bars 1 mm." figureDoi="http://doi.org/10.5281/zenodo.10980754" httpUri="https://zenodo.org/record/10980754/files/figure.png" pageId="5" pageNumber="102">Fig. 4</figureCitation>
|
||
) and serial cross-sections (
|
||
<figureCitation id="13082A2649122D2FE9ADFDA0FB8B1439" box="[982,1051,586,613]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="5" pageNumber="102">Fig. 5</figureCitation>
|
||
). The pulp cavity of many spines was filled with calcite and quartz, as well as opaque minerals such as iron oxides. The pulp cavity was located slightly off-center in the spine (as seen in cross-sections) at the proximal end of the denticulated region (
|
||
<figureCitation id="13082A2649122D2FEE8AFD20FAA314B9" box="[1265,1331,714,741]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="5" pageNumber="102">Fig. 5</figureCitation>
|
||
), but became closer to the posterior side of the spine in the non-denticulated region (
|
||
<figureCitation id="13082A2649122D2FE9C1FCE0FB981578" box="[954,1032,778,804]" captionStart="Fig" captionStartId="8.[151,184,1485,1507]" captionTargetBox="[160,810,170,1462]" captionTargetId="figure-550@8.[153,823,164,1453]" captionTargetPageId="8" captionText="Fig. 6. Cross-sections of dorsal spines (non-denticulated region) of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA. Comparison between the smallest, specimen HMNS-T1 (A), and the largest Orthacanthus dorsal spine sampled, specimen HMNS-J1 (B). Posterior sides of the spines are pointing to the top of the figure." figureDoi="http://doi.org/10.5281/zenodo.10980758" httpUri="https://zenodo.org/record/10980758/files/figure.png" pageId="5" pageNumber="102">Figs. 6</figureCitation>
|
||
,
|
||
<figureCitation id="13082A2649122D2FEE68FCE1FBB31579" box="[1043,1059,779,805]" captionStart="Fig" captionStartId="9.[98,131,1319,1341]" captionTargetBox="[120,1458,161,1295]" captionTargetId="figure-292@9.[121,1458,160,1269]" captionTargetPageId="9" captionText="Fig. 7. Cross-section of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J7 non-denticulated region) showing color-banding in centrifugal trabecular dentine and growth lines in lamellar dentine. A. General view (posterior side of spine towards the top of the figure). B, C. Details of periphery showing pairs of growth lines (marked by arrows) in the centrifugal lamellar dentine. D. Detail of interglobular spaces within the centripetal lamellar dentine (arrows denote interglobular spaces)." figureDoi="http://doi.org/10.5281/zenodo.10980760" httpUri="https://zenodo.org/record/10980760/files/figure.png" pageId="5" pageNumber="102">7</figureCitation>
|
||
). The wall of the spine was composed of two structural components—an outer layer of centrifugally growing dentine (growing outward from the periphery of the spine), and a layer of centripetally deposited dentine (growing inward) lining the pulp cavity.
|
||
</paragraph>
|
||
<paragraph id="8B8C36A349122D2FE935FC41FB08137A" blockId="5.[808,1482,522,1960]" pageId="5" pageNumber="102">
|
||
The centrifugal dentine was composed primarily of highly vascular trabecular dentinal layers. Centrifugal lamellar dentine was in the most distal parts of the dentinal layers and at the periphery of large spines. Most spines had occasional enlarged vascular canals in the outer half of the spine wall (
|
||
<figureCitation id="13082A2649122D2FE9D4FBA1FB981239" box="[943,1032,1099,1125]" captionStart="Fig" captionStartId="8.[151,184,1485,1507]" captionTargetBox="[160,810,170,1462]" captionTargetId="figure-550@8.[153,823,164,1453]" captionTargetPageId="8" captionText="Fig. 6. Cross-sections of dorsal spines (non-denticulated region) of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA. Comparison between the smallest, specimen HMNS-T1 (A), and the largest Orthacanthus dorsal spine sampled, specimen HMNS-J1 (B). Posterior sides of the spines are pointing to the top of the figure." figureDoi="http://doi.org/10.5281/zenodo.10980758" httpUri="https://zenodo.org/record/10980758/files/figure.png" pageId="5" pageNumber="102">Fig. 6B</figureCitation>
|
||
, see also
|
||
<figureCitation id="13082A2649122D2FEE01FBA1FB641239" box="[1146,1268,1099,1126]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="5" pageNumber="102">Fig. 5A, C</figureCitation>
|
||
). Dentinal tubules radiated out from the outermost lamellae of denteons, although some vascular canals were simple and did not have distinct lamellae. When a major growth line was present, denteons below the growth line were more developed than those outside of the line. Colour banding was apparent in most spines (
|
||
<figureCitation id="13082A2649122D2FE9C0FAE6FBAF137B" box="[955,1087,1292,1319]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="5" pageNumber="102">Figs. 5A–D</figureCitation>
|
||
,
|
||
<figureCitation id="13082A2649122D2FEE30FAE6FBFF137A" box="[1099,1135,1292,1318]" captionStart="Fig" captionStartId="8.[151,184,1485,1507]" captionTargetBox="[160,810,170,1462]" captionTargetId="figure-550@8.[153,823,164,1453]" captionTargetPageId="8" captionText="Fig. 6. Cross-sections of dorsal spines (non-denticulated region) of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA. Comparison between the smallest, specimen HMNS-T1 (A), and the largest Orthacanthus dorsal spine sampled, specimen HMNS-J1 (B). Posterior sides of the spines are pointing to the top of the figure." figureDoi="http://doi.org/10.5281/zenodo.10980758" httpUri="https://zenodo.org/record/10980758/files/figure.png" pageId="5" pageNumber="102">6A</figureCitation>
|
||
,
|
||
<figureCitation id="13082A2649122D2FEE01FAE6FB1A137A" box="[1146,1162,1292,1318]" captionStart="Fig" captionStartId="9.[98,131,1319,1341]" captionTargetBox="[120,1458,161,1295]" captionTargetId="figure-292@9.[121,1458,160,1269]" captionTargetPageId="9" captionText="Fig. 7. Cross-section of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J7 non-denticulated region) showing color-banding in centrifugal trabecular dentine and growth lines in lamellar dentine. A. General view (posterior side of spine towards the top of the figure). B, C. Details of periphery showing pairs of growth lines (marked by arrows) in the centrifugal lamellar dentine. D. Detail of interglobular spaces within the centripetal lamellar dentine (arrows denote interglobular spaces)." figureDoi="http://doi.org/10.5281/zenodo.10980760" httpUri="https://zenodo.org/record/10980760/files/figure.png" pageId="5" pageNumber="102">7</figureCitation>
|
||
).
|
||
</paragraph>
|
||
<paragraph id="8B8C36A349122D2FE935FAC6FBDB105A" blockId="5.[808,1482,522,1960]" pageId="5" pageNumber="102">
|
||
The centripetal dentine mainly exhibited a lamellar structure with incremental deposition of hard tissue (
|
||
<figureCitation id="13082A2649122D2FEF0CFAA6FA55133A" box="[1399,1477,1356,1382]" captionStart="Fig" captionStartId="6.[151,184,1654,1674]" captionTargetBox="[152,1533,163,1628]" captionTargetId="figure-187@6.[152,1515,184,1288]" captionTargetPageId="6" captionText="Fig. 4. Serial longitudinal sections of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-T2, where A represents the most proximal section and E is the most distal. Samples C–E include the denticulate region. Photos of the sections (A1–E1), interpretative drawings (A2–E2). Scale bars 1 mm." figureDoi="http://doi.org/10.5281/zenodo.10980754" httpUri="https://zenodo.org/record/10980754/files/figure.png" pageId="5" pageNumber="102">Figs. 4</figureCitation>
|
||
,
|
||
<figureCitation id="13082A2649122D2FE953FA86FCA813DB" box="[808,824,1388,1415]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="5" pageNumber="102">5</figureCitation>
|
||
). Centripetal lamellar dentine thickened distally, and filled the pulp cavity of the most distal sections. Spines HMNS-T2 and HMNS-J3, shown in
|
||
<figureCitation id="13082A2649122D2FEE2FFA46FB33139A" box="[1108,1187,1452,1478]" captionStart="Fig" captionStartId="6.[151,184,1654,1674]" captionTargetBox="[152,1533,163,1628]" captionTargetId="figure-187@6.[152,1515,184,1288]" captionTargetPageId="6" captionText="Fig. 4. Serial longitudinal sections of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-T2, where A represents the most proximal section and E is the most distal. Samples C–E include the denticulate region. Photos of the sections (A1–E1), interpretative drawings (A2–E2). Scale bars 1 mm." figureDoi="http://doi.org/10.5281/zenodo.10980754" httpUri="https://zenodo.org/record/10980754/files/figure.png" pageId="5" pageNumber="102">Figs. 4</figureCitation>
|
||
and
|
||
<figureCitation id="13082A2649122D2FEE9BFA46FB7F139B" box="[1248,1263,1452,1479]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="5" pageNumber="102">5</figureCitation>
|
||
, respectively, each had a region of centripetal trabecular dentine in the pulp cavity near the distal end.
|
||
</paragraph>
|
||
<paragraph id="8B8C36A349122D2CE935F9E7FD2F117B" blockId="5.[808,1482,522,1960]" lastBlockId="6.[151,825,1774,1959]" lastPageId="6" lastPageNumber="103" pageId="5" pageNumber="102">
|
||
Though the smallest spine sampled (HMNS-T1) was sectioned just proximal to the denticulate region, only one dentine layer (SP1) was present. This layer contained no growth lines, changes in colour or vascular patterns, or lamellar dentine (
|
||
<figureCitation id="13082A2649122D2FE94BF967FC1510F4" box="[816,901,1677,1704]" captionStart="Fig" captionStartId="8.[151,184,1485,1507]" captionTargetBox="[160,810,170,1462]" captionTargetId="figure-550@8.[153,823,164,1453]" captionTargetPageId="8" captionText="Fig. 6. Cross-sections of dorsal spines (non-denticulated region) of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA. Comparison between the smallest, specimen HMNS-T1 (A), and the largest Orthacanthus dorsal spine sampled, specimen HMNS-J1 (B). Posterior sides of the spines are pointing to the top of the figure." figureDoi="http://doi.org/10.5281/zenodo.10980758" httpUri="https://zenodo.org/record/10980758/files/figure.png" pageId="5" pageNumber="102">Fig. 6A</figureCitation>
|
||
). However, in thin-sections made near or through the denticulate region of larger spines, centrifugal and centripetal lamellar dentine were present, and in some cases, the dentine could be divided into two depositional layers, separated by a major growth line (see
|
||
<figureCitation id="13082A2649122D2FEE3DF8E7FB241174" box="[1094,1204,1805,1832]" captionStart-0="Fig" captionStart-1="Fig" captionStart-2="Fig" captionStartId-0="6.[151,184,1654,1674]" captionStartId-1="7.[98,131,1066,1088]" captionStartId-2="8.[151,184,1485,1507]" captionTargetBox-0="[152,1533,163,1628]" captionTargetBox-1="[126,1452,161,1043]" captionTargetBox-2="[160,810,170,1462]" captionTargetId-0="figure-187@6.[152,1515,184,1288]" captionTargetId-1="figure-434@7.[241,1453,161,1017]" captionTargetId-2="figure-550@8.[153,823,164,1453]" captionTargetPageId-0="6" captionTargetPageId-1="7" captionTargetPageId-2="8" captionText-0="Fig. 4. Serial longitudinal sections of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-T2, where A represents the most proximal section and E is the most distal. Samples C–E include the denticulate region. Photos of the sections (A1–E1), interpretative drawings (A2–E2). Scale bars 1 mm." captionText-1="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." captionText-2="Fig. 6. Cross-sections of dorsal spines (non-denticulated region) of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA. Comparison between the smallest, specimen HMNS-T1 (A), and the largest Orthacanthus dorsal spine sampled, specimen HMNS-J1 (B). Posterior sides of the spines are pointing to the top of the figure." figureDoi-0="http://doi.org/10.5281/zenodo.10980754" figureDoi-1="http://doi.org/10.5281/zenodo.10980756" figureDoi-2="http://doi.org/10.5281/zenodo.10980758" httpUri-0="https://zenodo.org/record/10980754/files/figure.png" httpUri-1="https://zenodo.org/record/10980756/files/figure.png" httpUri-2="https://zenodo.org/record/10980758/files/figure.png" pageId="5" pageNumber="102">Figs. 4–6</figureCitation>
|
||
). Dentine layer SP1 was thickest in the distal portion of spines, gradually became thinner proximally, and was not present in most fragments proximal to the denticulate region. Dentine layer SP2 was thickest proximally and was not present in the most distal portions of denticulate regions (see
|
||
<figureCitation id="13082A2649112D2CEBD7F904FE60115B" box="[428,496,1774,1799]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="6" pageNumber="103">Fig. 5</figureCitation>
|
||
). Where both dentine layers were present, a major growth line separated them.
|
||
</paragraph>
|
||
<caption id="DF4C662B49112D2CEAECF99CFD23109E" ID-DOI="http://doi.org/10.5281/zenodo.10980754" ID-Zenodo-Dep="10980754" httpUri="https://zenodo.org/record/10980754/files/figure.png" pageId="6" pageNumber="103" startId="6.[151,184,1654,1674]" targetBox="[152,1533,163,1628]" targetPageId="6" targetType="figure">
|
||
<paragraph id="8B8C36A349112D2CEAECF99CFD23109E" blockId="6.[151,1534,1653,1733]" pageId="6" pageNumber="103">
|
||
Fig. 4. Serial longitudinal sections of dorsal spine of
|
||
<taxonomicName id="4C334D2049112D2CE803F99FFC7B10D6" authority="(Cope, 1884)" baseAuthorityName="Cope" baseAuthorityYear="1884" box="[632,1003,1653,1674]" class="Liliopsida" family="Poaceae" genus="Orthacanthus" kingdom="Plantae" order="Poales" pageId="6" pageNumber="103" phylum="Tracheophyta" rank="species" species="platypternus">
|
||
<emphasis id="B947EAB149112D2CE803F99FFCFB10D6" box="[632,875,1653,1674]" italics="true" pageId="6" pageNumber="103">Orthacanthus platypternus</emphasis>
|
||
(
|
||
<bibRefCitation id="EFA24B5249112D2CE903F99CFC7410D6" author="Cope, E. D." box="[888,996,1654,1674]" pageId="6" pageNumber="103" pagination="572 - 590" refId="ref15299" refString="Cope, E. D. 1884. On the structure of the skull in the elasmobranch genus Didymodus. Proceedings of the American Philosophical Society 21: 572 - 590." type="journal article" year="1884">Cope, 1884</bibRefCitation>
|
||
)
|
||
</taxonomicName>
|
||
, Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-T2, where A represents the most proximal section and E is the most distal. Samples C–E include the denticulate region. Photos of the sections (A
|
||
<subScript id="17B734E649112D2CEAD4F95DFF271099" attach="left" box="[175,183,1719,1733]" fontSize="6" pageId="6" pageNumber="103">1</subScript>
|
||
–E
|
||
<subScript id="17B734E649112D2CEAABF95DFF481099" attach="left" box="[208,216,1719,1733]" fontSize="6" pageId="6" pageNumber="103">1</subScript>
|
||
), interpretative drawings (A
|
||
<subScript id="17B734E649112D2CEBA1F95DFE721099" attach="left" box="[474,482,1719,1733]" fontSize="6" pageId="6" pageNumber="103">2</subScript>
|
||
–E
|
||
<subScript id="17B734E649112D2CEB80F95DFD931099" attach="left" box="[507,515,1719,1733]" fontSize="6" pageId="6" pageNumber="103">2</subScript>
|
||
). Scale bars 1 mm.
|
||
</paragraph>
|
||
</caption>
|
||
<paragraph id="8B8C36A349112D2CEAC6F8C4FA6F11DB" blockId="6.[151,825,1774,1959]" lastBlockId="6.[862,1535,1774,1959]" pageId="6" pageNumber="103">
|
||
Major growth lines were most evident in spines HMNS-T2 and HMNS-J3 (
|
||
<figureCitation id="13082A2649112D2CEBAEF8A4FDB7113B" box="[469,551,1870,1895]" captionStart="Fig" captionStartId="6.[151,184,1654,1674]" captionTargetBox="[152,1533,163,1628]" captionTargetId="figure-187@6.[152,1515,184,1288]" captionTargetPageId="6" captionText="Fig. 4. Serial longitudinal sections of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-T2, where A represents the most proximal section and E is the most distal. Samples C–E include the denticulate region. Photos of the sections (A1–E1), interpretative drawings (A2–E2). Scale bars 1 mm." figureDoi="http://doi.org/10.5281/zenodo.10980754" httpUri="https://zenodo.org/record/10980754/files/figure.png" pageId="6" pageNumber="103">Figs. 4</figureCitation>
|
||
,
|
||
<figureCitation id="13082A2649112D2CE84DF8A4FDD6113B" box="[566,582,1870,1895]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="6" pageNumber="103">5</figureCitation>
|
||
). A growth line was evident in four out of five cross-sections of specimen HMNS-J3 (all except for the most distal) and can be seen most clearly in
|
||
<figureCitation id="13082A2649112D2CEE75F904FBF4115B" box="[1038,1124,1774,1799]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="6" pageNumber="103">Fig. 5A</figureCitation>
|
||
. Vascular canals to the inside of the growth line were lined with lamellae, whereas vascular canals to the outside of the ring were not. In serial longitudinal sections (
|
||
<figureCitation id="13082A2649112D2CE9B2F8A4FB9E113B" box="[969,1038,1870,1895]" captionStart="Fig" captionStartId="6.[151,184,1654,1674]" captionTargetBox="[152,1533,163,1628]" captionTargetId="figure-187@6.[152,1515,184,1288]" captionTargetPageId="6" captionText="Fig. 4. Serial longitudinal sections of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-T2, where A represents the most proximal section and E is the most distal. Samples C–E include the denticulate region. Photos of the sections (A1–E1), interpretative drawings (A2–E2). Scale bars 1 mm." figureDoi="http://doi.org/10.5281/zenodo.10980754" httpUri="https://zenodo.org/record/10980754/files/figure.png" pageId="6" pageNumber="103">Fig. 4</figureCitation>
|
||
), the major growth line gradually projected toward and eventually contacted the pulp cavity, proximally.
|
||
</paragraph>
|
||
<paragraph id="8B8C36A349112D2DE9FFF864FC93130A" blockId="6.[862,1535,1774,1959]" lastBlockId="7.[98,771,1175,1960]" lastPageId="7" lastPageNumber="104" pageId="6" pageNumber="103">
|
||
Some of the larger spines also had minor growth lines in the lamellar dentine at the periphery of SP2 (
|
||
<figureCitation id="13082A2649102D2DE80CFB72FD2912EE" box="[631,697,1175,1202]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="7" pageNumber="104">Fig. 5</figureCitation>
|
||
,
|
||
<figureCitation id="13082A2649102D2DE8BDFB72FD4612EE" box="[710,726,1176,1202]" captionStart="Fig" captionStartId="9.[98,131,1319,1341]" captionTargetBox="[120,1458,161,1295]" captionTargetId="figure-292@9.[121,1458,160,1269]" captionTargetPageId="9" captionText="Fig. 7. Cross-section of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J7 non-denticulated region) showing color-banding in centrifugal trabecular dentine and growth lines in lamellar dentine. A. General view (posterior side of spine towards the top of the figure). B, C. Details of periphery showing pairs of growth lines (marked by arrows) in the centrifugal lamellar dentine. D. Detail of interglobular spaces within the centripetal lamellar dentine (arrows denote interglobular spaces)." figureDoi="http://doi.org/10.5281/zenodo.10980760" httpUri="https://zenodo.org/record/10980760/files/figure.png" pageId="7" pageNumber="104">7</figureCitation>
|
||
). In specimen HMNS-J3, three minor growth lines were fine, dark and evenly spaced (
|
||
<figureCitation id="13082A2649102D2DEBF8FB33FE4912A8" box="[387,473,1241,1268]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="7" pageNumber="104">Fig. 5B</figureCitation>
|
||
). In specimen HMNS-J7, growth lines were arranged in at least three pairs (
|
||
<figureCitation id="13082A2649102D2DE8E4FB10FD651349" box="[671,757,1274,1301]" captionStart="Fig" captionStartId="9.[98,131,1319,1341]" captionTargetBox="[120,1458,161,1295]" captionTargetId="figure-292@9.[121,1458,160,1269]" captionTargetPageId="9" captionText="Fig. 7. Cross-section of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J7 non-denticulated region) showing color-banding in centrifugal trabecular dentine and growth lines in lamellar dentine. A. General view (posterior side of spine towards the top of the figure). B, C. Details of periphery showing pairs of growth lines (marked by arrows) in the centrifugal lamellar dentine. D. Detail of interglobular spaces within the centripetal lamellar dentine (arrows denote interglobular spaces)." figureDoi="http://doi.org/10.5281/zenodo.10980760" httpUri="https://zenodo.org/record/10980760/files/figure.png" pageId="7" pageNumber="104">Fig. 7B</figureCitation>
|
||
), although the spine fragment was not long enough to determine if these growth lines were major or minor growth lines.
|
||
</paragraph>
|
||
<caption id="DF4C662B49102D2DEA19FBC0FDEC1224" ID-DOI="http://doi.org/10.5281/zenodo.10980756" ID-Zenodo-Dep="10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="7" pageNumber="104" startId="7.[98,131,1066,1088]" targetBox="[126,1452,161,1043]" targetPageId="7" targetType="figure">
|
||
<paragraph id="8B8C36A349102D2DEA19FBC0FDEC1224" blockId="7.[98,1481,1066,1144]" pageId="7" pageNumber="104">
|
||
Fig. 5. Serial cross-sections (
|
||
<emphasis id="B947EAB149102D2DEB15FBC0FEEE1263" bold="true" box="[366,382,1066,1087]" pageId="7" pageNumber="104">A</emphasis>
|
||
,
|
||
<emphasis id="B947EAB149102D2DEBF0FBC0FE0B121C" bold="true" box="[395,411,1066,1088]" pageId="7" pageNumber="104">C</emphasis>
|
||
,
|
||
<emphasis id="B947EAB149102D2DEBD3FBC0FE281263" bold="true" box="[424,440,1066,1087]" pageId="7" pageNumber="104">D</emphasis>
|
||
) of dorsal spine of
|
||
<taxonomicName id="4C334D2049102D2DE80AFBC6FC78121C" authority="(Cope, 1884)" baseAuthorityName="Cope" baseAuthorityYear="1884" box="[625,1000,1066,1088]" class="Liliopsida" family="Poaceae" genus="Orthacanthus" kingdom="Plantae" order="Poales" pageId="7" pageNumber="104" phylum="Tracheophyta" rank="species" species="platypternus">
|
||
<emphasis id="B947EAB149102D2DE80AFBC6FCF5121C" box="[625,869,1068,1088]" italics="true" pageId="7" pageNumber="104">Orthacanthus platypternus</emphasis>
|
||
(
|
||
<bibRefCitation id="EFA24B5249102D2DE908FBC0FC71121C" author="Cope, E. D." box="[883,993,1066,1088]" pageId="7" pageNumber="104" pagination="572 - 590" refId="ref15299" refString="Cope, E. D. 1884. On the structure of the skull in the elasmobranch genus Didymodus. Proceedings of the American Philosophical Society 21: 572 - 590." type="journal article" year="1884">Cope, 1884</bibRefCitation>
|
||
)
|
||
</taxonomicName>
|
||
, Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal.
|
||
<emphasis id="B947EAB149102D2DE9CAFBACFC501207" bold="true" box="[945,960,1094,1115]" pageId="7" pageNumber="104">B</emphasis>
|
||
. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows).
|
||
</paragraph>
|
||
</caption>
|
||
<paragraph id="8B8C36A349102D2DEAFCFAB7FF6013A7" blockId="7.[98,771,1175,1960]" pageId="7" pageNumber="104">
|
||
Growth lines, such as those seen in
|
||
<figureCitation id="13082A2649102D2DE854FAB7FD141324" box="[559,644,1373,1400]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="7" pageNumber="104">Fig. 5B</figureCitation>
|
||
, were also present in the lamellar dentine around the pulp cavity of four spines (specimens HMNS-J1, J3, J7, J8). In most specimens, colour-banding and growth lines usually circumvented vascular canals.
|
||
</paragraph>
|
||
<paragraph id="8B8C36A349102D2DEAFCF9E8FDFC1178" blockId="7.[98,771,1175,1960]" pageId="7" pageNumber="104">
|
||
Cross-sections of specimen HMNS-J3 show the orthodentine (dark colour) forming the distal part of the denticles see
|
||
<figureCitation id="13082A2649102D2DEAE1F9AEFF661003" box="[154,246,1604,1631]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="7" pageNumber="104">Fig. 5D</figureCitation>
|
||
). The inner region of denticles consisted of white dentine, with many long dentinal tubules radiating outward from at least one vascular canal at the base of or in the innermost region of the denticle. In serial longitudinal sections of HMNS-T2, the denticulate region did not extend to the entire length of SP1 and all denticles present on the available fragment were added to SP2 (
|
||
<figureCitation id="13082A2649102D2DE867F8E0FDCF1178" box="[540,607,1802,1828]" captionStart="Fig" captionStartId="6.[151,184,1654,1674]" captionTargetBox="[152,1533,163,1628]" captionTargetId="figure-187@6.[152,1515,184,1288]" captionTargetPageId="6" captionText="Fig. 4. Serial longitudinal sections of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-T2, where A represents the most proximal section and E is the most distal. Samples C–E include the denticulate region. Photos of the sections (A1–E1), interpretative drawings (A2–E2). Scale bars 1 mm." figureDoi="http://doi.org/10.5281/zenodo.10980754" httpUri="https://zenodo.org/record/10980754/files/figure.png" pageId="7" pageNumber="104">Fig. 4</figureCitation>
|
||
).
|
||
</paragraph>
|
||
<paragraph id="8B8C36A349102D2DEAFCF8C1FAD113E6" blockId="7.[98,771,1175,1960]" lastBlockId="7.[808,1481,1176,1960]" pageId="7" pageNumber="104">
|
||
Interglobular spaces were found in interdenteonal areas of all spines. These spaces were generally more numerous near the pulp cavity of all spines, and were especially dense in proximal sections, near the pulp cavity of larger spines. In proximal specimen HMNS-J7, interglobular spaces and iron oxides were extremely dense in some regions near the pulp cavity and also markedly decreased in number and size at the border between the innermost layer of white centripetal dentine and the following, darker coloured trabecular dentine of the spine wall (
|
||
<figureCitation id="13082A2649102D2DEE2EFAD7FB3F130B" box="[1109,1199,1341,1367]" captionStart="Fig" captionStartId="9.[98,131,1319,1341]" captionTargetBox="[120,1458,161,1295]" captionTargetId="figure-292@9.[121,1458,160,1269]" captionTargetPageId="9" captionText="Fig. 7. Cross-section of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J7 non-denticulated region) showing color-banding in centrifugal trabecular dentine and growth lines in lamellar dentine. A. General view (posterior side of spine towards the top of the figure). B, C. Details of periphery showing pairs of growth lines (marked by arrows) in the centrifugal lamellar dentine. D. Detail of interglobular spaces within the centripetal lamellar dentine (arrows denote interglobular spaces)." figureDoi="http://doi.org/10.5281/zenodo.10980760" httpUri="https://zenodo.org/record/10980760/files/figure.png" pageId="7" pageNumber="104">Fig. 7D</figureCitation>
|
||
). Spine HMNS-J8 had a similar distinct decrease in interglobular spaces where the centripetal lamellar dentine lining the pulp cavity met the centrifugal trabecular dentine of the spine wall.
|
||
</paragraph>
|
||
<paragraph id="8B8C36A349102D22E935FA2BFE8911FB" blockId="7.[808,1481,1176,1960]" lastBlockId="8.[151,824,1643,1960]" lastPageId="8" lastPageNumber="105" pageId="7" pageNumber="104">
|
||
In several spines, calcospherites on the periphery of the spine wall formed a translucent border (
|
||
<figureCitation id="13082A2649102D2DEE8CFA0BFADF13A0" box="[1271,1359,1505,1532]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="7" pageNumber="104">Fig. 5B</figureCitation>
|
||
). Globular calcospherites were most clearly visible on the outer edge of specimen HMNS-J3, and were associated with numerous small interglobular spaces. Interglobular spaces represent poorly mineralized regions between calcospherites, which did not completely fuse during dentinogenesis (
|
||
<bibRefCitation id="EFA24B5249102D2DEF0CF96CFCF4109E" author="Currey, J. D." pageId="7" pageNumber="104" refId="ref15331" refString="Currey, J. D. 2006. Bones: Structure and Mechanics. Ed. 2. 436 pp. Princeton University Press, Princeton." type="book" year="2006">Currey 2006</bibRefCitation>
|
||
). In most cases, interglobular spaces were distributed sporadically through the spine wall, and in the highest numbers and density near the pulp cavity of spines. The high density of interglobular spaces within the centripetal lamellar dentine of specimens HMNS-J7 and HMNS-J8 supports the hypothesis that younger dentine was hypomineralized and became more mineralized as the individual aged (as suggested by
|
||
<bibRefCitation id="EFA24B5249102D2DE9B3F864FB1F11F4" author="Soler-Gijon, R." box="[968,1167,1934,1960]" pageId="7" pageNumber="104" pagination="1 - 45" refId="ref18578" refString="Soler-Gijon, R. 1999. Occipital Spine of Orthacanthus (Xenacanthidae, Elasmobranchii): Structure and Growth. Journal of Morphology 242: 1 - 45." type="journal article" year="1999">Soler-Gijón 1999</bibRefCitation>
|
||
). Hypomineralized dentine (particularly that near the pulp cavity) was probably more susceptible to diagenesis and degradation following invasion of microorganisms, leading to the deposition of dark, opaque minerals (such as iron oxide) seen associated with interglobular spaces of the centripetal lamellar dentine of some spines (
|
||
<figureCitation id="13082A26491F2D22EB4EF8E6FE1D117B" box="[309,397,1804,1831]" captionStart="Fig" captionStartId="9.[98,131,1319,1341]" captionTargetBox="[120,1458,161,1295]" captionTargetId="figure-292@9.[121,1458,160,1269]" captionTargetPageId="9" captionText="Fig. 7. Cross-section of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J7 non-denticulated region) showing color-banding in centrifugal trabecular dentine and growth lines in lamellar dentine. A. General view (posterior side of spine towards the top of the figure). B, C. Details of periphery showing pairs of growth lines (marked by arrows) in the centrifugal lamellar dentine. D. Detail of interglobular spaces within the centripetal lamellar dentine (arrows denote interglobular spaces)." figureDoi="http://doi.org/10.5281/zenodo.10980760" httpUri="https://zenodo.org/record/10980760/files/figure.png" pageId="8" pageNumber="105">Fig. 7D</figureCitation>
|
||
) (
|
||
<bibRefCitation id="EFA24B52491F2D22EBDDF8E6FD02117B" author="Turner-Walker, G." box="[422,658,1804,1831]" pageId="8" pageNumber="105" pagination="3 - 29" refId="ref19092" refString="Turner-Walker, G. 2008. The chemical and microbial degradation of bones and teeth. In: R. Pinhasi and S. Mays (eds.), Advances in Human Palaeopathology, 3 - 29. The Atrium, Southern Gate, Chichester." type="book chapter" year="2008">Turner-Walker 2008</bibRefCitation>
|
||
). Altered dentine and interglobular spaces filled by authigenic minerals are relatively common in fossil chondrichthyan and acanthodian fin-spines (see discussion and references in
|
||
<bibRefCitation id="EFA24B52491F2D22E89CF887FE9E11FB" author="Botella, H. & Martinez-Perez, C. & Soler-Gijon, R." pageId="8" pageNumber="105" pagination="761 - 783" refId="ref14816" refString="Botella, H., Martinez-Perez, C., and Soler-Gijon, R. 2012. Machaeracanthus goujeti n. sp. (Acanthodii) from the Lower Devonian of Spain and northwest France, with special reference to spine histology. Geodiversitas 34: 761 - 783." type="journal article" year="2012">Botella et al. 2012</bibRefCitation>
|
||
).
|
||
</paragraph>
|
||
<paragraph id="8B8C36A3491F2D22E9FFFF74FA6514C0" blockId="8.[862,1535,158,668]" pageId="8" pageNumber="105">
|
||
The colour-banding present in almost all spines was also noted by
|
||
<bibRefCitation id="EFA24B52491F2D22E9BFFF54FBF21685" author="Maisey, J. G." box="[964,1122,190,217]" pageId="8" pageNumber="105" pagination="657 - 666" refId="ref17219" refString="Maisey, J. G. 1978. Growth and form of finspines in hybodont sharks. Palaeontology 21: 657 - 666." type="journal article" year="1978">Maisey (1978)</bibRefCitation>
|
||
in finspines of hybodont sharks. The colour of fossil dentine can be related to diagenesis, where well-preserved dentine often appears reddish in colour, whereas layers of dentine exposed to the environment may be white-coloured. However, in some cases in this study, a major growth line separated two colour bands as well as two different stages in denteon development (such as in
|
||
<figureCitation id="13082A26491F2D22EFE5FE6AFA6217C6" box="[1438,1522,383,410]" captionStart="Fig" captionStartId="7.[98,131,1066,1088]" captionTargetBox="[126,1452,161,1043]" captionTargetId="figure-434@7.[241,1453,161,1017]" captionTargetPageId="7" captionText="Fig. 5. Serial cross-sections (A, C, D) of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-J3, where A represents the most proximal section and D is the most distal. B. Detail of section in A showing three minor growth lines close to the base of the right denticle in the figure (arrows)." figureDoi="http://doi.org/10.5281/zenodo.10980756" httpUri="https://zenodo.org/record/10980756/files/figure.png" pageId="8" pageNumber="105">Fig. 5A</figureCitation>
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), suggesting that colour banding can also be related to dentine deposition. The smallest spine sampled here (HMNS-T1) corresponded to a very young juvenile individual as indicated by the short denticulation, and lacked colour banding. The largest spine sampled (HMNS-J1) also showed weaker colour banding than most other spines, probably due to a very fast mineralization during dentinogenesis (see discussion below, in section “Histology and skeletochronology”).
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</paragraph>
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</subSubSection>
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</treatment>
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</document> |