Anshunsaurus

{{Short description|Extinct genus of reptiles}} {{Automatic taxobox | fossil_range = Middle Triassic, {{fossil range|237|228}} |image = Anshunsaurus huangguoshuensis NTM.jpg |image_upright = 1.15 |image_caption = Fossil specimen of ''A. huangguoshuensis'', National Taiwan Museum | taxon = Anshunsaurus | authority = Liu, 1999 | subdivision_ranks = Species | subdivision = * {{extinct}}''A. huangguoshuensis'' Liu, 1999 (type) * {{extinct}}''A. wushaensis'' Rieppel ''et al.'', 2006 * {{extinct}}''A. huangnihensis'' Cheng ''et al.'', 2007 }}

'''''Anshunsaurus''''' is a genus of thalattosaurs within the family Askeptosauridae. Fossils have been found from Middle Triassic deposits in Guizhou, China. Three species are known: the type species ''A. huangguoshuensis'' (named in 1999),<ref name=":0">{{Cite journal|last=Liu|first=Jun|date=1999-07-01|title=Sauropterygian from Triassic of Guizhou, China|url=https://www.academia.edu/1882074|journal=Chinese Science Bulletin|language=en|volume=44|issue=14|pages=1312–1316|doi=10.1007/BF02885852|bibcode=1999ChSBu..44.1312L|s2cid=129934751|issn=1861-9541}}</ref> the slightly older species ''A. wushaensis'' (named in 2006),<ref name="RLL06" /> and the species ''A. huangnihensis'' (named in 2007).<ref name="CCW07" />

==Description and species== ''Anshunsaurus'' was a marine reptile with a long neck, slender skull, and long, paddle-like tail. In comparison to its long trunk, the limbs are very small. ''Anshunsaurus'' is characterized by a long jugal bone in the skull, fused postorbital and postfrontal bones around the eyes, a maxilla that forms part of the margin of the eye socket, a humerus with large crests, and a large fibula.<ref name="LR05" />

The type species of ''Anshunsaurus'', ''A. huangguoshuensis'', was named in 1999 from the Ladinian or Carnian age Falang Formation in Guanling County. Although several complete skeletons are known, most specimens are crushed in either dorsal (top) or ventral (bottom) view. The holotype of ''A. huangguoshuensis'', IVPP V11835, is preserved in dorsal view while a second specimen, IVPP V11834, is preserved in ventral view. Based on these specimens, ''A. huangguoshuensis'' grew to about {{convert|3.5|m|ft}} in length. Although the tip is not preserved in any specimen, the tail made up at least half of the animal's length.<ref name="LR05">{{cite journal |last=Liu |first=J. |author2=Rieppel, O. |year=2005 |title=Restudy of ''Anshunsaurus huangguoshuensis'' (Reptilia: Thalattosauria) from the Middle Triassic of Guizhou, China |journal=American Museum Novitates |issue=3488 |pages=1–34 |issn=0003-0082 |url=http://digitallibrary.amnh.org/dspace/bitstream/2246/5657/1/N3488.pdf |doi=10.1206/0003-0082(2005)488[0001:roahrt]2.0.co;2|s2cid=55642315 }}</ref> A juvenile specimen of ''A. huangguoshuensis'' was described in 2015.<ref>{{Cite journal|last=Maisch|first=Michael W.|date=2015|title=A juvenile specimen of ''Anshunsaurus huangguoshuensis'' LIU, 1999 (Diapsida: Thalattosauria) from the Upper Triassic of China|url=http://www.palaeodiversity.org/pdf/08/05Palaeodiversity_8-15_Maisch_3.pdf|journal=Paleodiversity|volume=8|pages=71–87}}</ref>

A second species, ''A. wushaensis'', was named in 2006 from Xingyi.<ref name="RLL06">{{cite journal|last=Rieppel|first=O.|author2=Liu, J.|author3=Li, C.|year=2006|title=A new species of the thalattosaur genus ''Anshunsaurus'' (Reptilia: Thalattosauria) from the Middle Triassic of Guizhou Province, southwestern China|url=https://www.researchgate.net/publication/311671429|journal=Vertebrata PalAsiatica|volume=44|pages=285–296}}</ref> ''A. wushaensis'' is slightly smaller than ''A. huangguoshuensis'' and has a smaller head relative to its body length. It also has shorter neural spines with ridges on their upper surface, a shorter fourth digit on the hand, a well-developed entepicondyle on the humerus, and a shorter jugal bone.<ref name="LJ07">{{cite journal |last=Liu |first=J. |year=2007 |title=A juvenile specimen of ''Anshunsaurus'' (Reptilia: Thalattosauria) |journal=American Museum Novitates |issue=3582 |pages=1–9 |issn=0003-0082 |url=http://digitallibrary.amnh.org/dspace/bitstream/2246/5875/1/N3582.pdf |doi=10.1206/0003-0082(2007)3582[1:ajsoar]2.0.co;2|s2cid=85916769 }}</ref> A juvenile specimen of ''A. wushaensis'' was described in 2007, making ''Anshunsaurus'' the only thalattosaur with a known growth series other than ''Xinpusaurus''. The pectoral and pelvic girdles are asymmetrical in this specimen, suggesting that the bones on the left and right sides of the animal did not ossify at the same rate while it was growing.<ref name="LJ07" />

In 2007 a third species of ''Anshunsaurus'', ''A. huangnihensis'', was described from Xingyi. It is distinguished from the other two species on the basis of the shape of its coracoid, a bone of the pectoral girdle.<ref name="CCW07">{{cite journal|last=Cheng|first=L.|author2=Chen, X.|author3=Wang, C.|year=2007|title=A new species of Late Triassic ''Anshunsaurus'' (Reptilia: Thalattosauria) from Guizhou Province|url=http://www.geojournals.cn/dzxbe/ch/reader/create_pdf.aspx?file_no=2007010154&flag=1&journal_id=dzxbe&year_id=2007|journal=Acta Geologica Sinica|language=zh|volume=81|issue=10|pages=1345–1351}}</ref>

==Classification== When it was first described in 1999, ''Anshunsaurus'' was thought to be a sauropterygian.<ref name=":0" /> In 2000, ''Anshunsaurus'' was reidentified as a thalattosaur and has remained in this group ever since.<ref>{{Cite journal|last1=Rieppel|first1=O.|last2=Liu|first2=J.|last3=Bucher|first3=H.|date=2000-09-25|title=The first record of a thalattosaur reptile from the Late Triassic of southern China (Guizhou Province, PR China)|url=https://www.researchgate.net/publication/254313780|journal=Journal of Vertebrate Paleontology|volume=20|issue=3|pages=507–514|doi=10.1671/0272-4634(2000)020[0507:TFROAT]2.0.CO;2|s2cid=140706921 |issn=0272-4634}}</ref> It was placed in the family Askeptosauridae along with the genus ''Askeptosaurus'' from Europe. Both thalattosaurs belong to Askeptosauroidea, a group characterized by their long necks and narrow skulls.<ref name="LR05" /> Of the three species of ''Anshunsaurus'', ''A. huangnihensis'' shares more features with other thalattosaurs such as ''Askeptosaurus'' and ''Endennasaurus''. These features suggest that ''A. huangnihensis'' is a transitional form between earlier thalattosaurs and the later species of ''Anshunsaurus''.<ref name=CCW07/><ref>{{Cite journal|last1=Cheng|first1=Long|last2=Chen|first2=Xiaohong|last3=Zhang|first3=Baomin|last4=Cai|first4=Yongjian|date=2011|title=New Study of Anshunsaurus huangnihensis Cheng, 2007 (Reptilia: Thalattosauria): Revealing its Transitional Position in Askeptosauridae|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1755-6724.2011.00584.x|journal=Acta Geologica Sinica - English Edition|language=en|volume=85|issue=6|pages=1231–1237|doi=10.1111/j.1755-6724.2011.00584.x|s2cid=129819570 |issn=1755-6724|url-access=subscription}}</ref>

==References== {{Reflist}}

Category:Thalattosauria Category:Middle Triassic reptiles of Asia Category:Prehistoric reptile genera