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{{Short description|Extinct genus of reptiles}}
{{Automatic taxobox
| taxon = Xinpusaurus
| fossil_range = [[
| image = Xinpusaurus-Tianjin Natural History Museum.jpg
| image_caption = Fossil specimen, [[Tianjin Natural History Museum]]
| authority = Yin, 2000
| subdivision_ranks = Species
| subdivision = * {{extinct}}''X. suni'' <small>Yin, 2000 ([[Type species|type]])</small>▼
▲* {{extinct}}''X. suni'' <small>Yin, 2000 ([[Type species|type]])</small>
* {{extinct}}''X. bamaolinensis'' <small>Cheng, 2003</small>
* {{extinct}}''X. kohi'' <small>Jiang ''et al.'', 2004</small>
* {{extinct}}''X. xingyiensis'' <small>Li ''et al.'', 2016</small>
}}
'''''Xinpusaurus''''' is an extinct [[genus]] of [[thalattosaur]] from the [[Late Triassic]] of [[Guanling]] in [[Guizhou, China]].
== Description ==
''Xinpusaurus'' is a thalattosaur, a group of triassic marine reptiles with long, paddle-like tails and short legs with independently movable digits. Specifically, it is a member of the group thalattosauroidea, which are characterized by their downturned [[premaxilla]]e. ''Xinpusaurus'' had a short neck, a massive [[Quadrate bone|quadrate]], and one of the few braincases preserved in thalattosaurs. The lower jaws of this genus show two different forms of [[dentary]]-[[Suprangular|surangular]] sutures, either a v-shaped suture with the surangular cutting into the dentary from the side (type 1) or an oblique suture with the surangular underlying the dentary (type 2). ''X. bamaolinensis'' preserves a type 2 suture while ''X. kohi'' has a type 1 suture. ''X. suni''<nowiki/>'s suture differs between specimens while ''X. xingyiensis'' seems to have a type 2 suture.<ref name="LJ13" /> The dentary is also narrow and shorter than the snout, with robust, pointed teeth in the front of its jaws and broad crushing teeth in the back of its jaws, suggesting that it fed on hard-shelled prey, although these adaptations are not as extreme as those of ''[[Concavispina]]'', which had exclusively short and blunt teeth.<ref name="LZLH13">{{Cite journal|last1=Liu|first1=J.|last2=Zhao|first2=L. J.|last3=Li|first3=C.|last4=He|first4=T.|year=2013|title=Osteology of ''Concavispina biseridens'' (Reptilia, Thalattosauria) from the Xiaowa Formation (Carnian), Guanling, Guizhou, China|journal=Journal of Paleontology|volume=87|issue=2|pages=341|doi=10.1666/12-059R1.1|bibcode=2013JPal...87..341L |s2cid=83684967}}</ref> This genus also has a uniquely upward-curving [[maxilla]], a wide proximal end of the [[humerus]], and a [[Radius (bone)|radius]] with a convex lateral edge and concave medial edge.<ref name=":1" />
''X. bamaolinensis'' and ''X. kohi'' had particularly elongated premaxillae, forming a narrow and pointed [[Rostrum (anatomy)|rostrum]]. However, the specimens with the longest snouts are also the smallest in other proportions, so this may be a juvenile trait and cannot be used to distinguish these species from ''X. suni''.<ref name="LJ13" />
''X. xingyiensis'' is the largest species known and is also probably the least advanced, as it does not have a posterior process of the jugal unlike the other species and shares some similarities with the genus ''Concavispina''.<ref name=":1" />
== History ==
''Xinpusaurus suni'' was first described by Yin et al. in 2000 based on four specimens: Gmr 010, 011, 012, and 013, with only Gmr 010 (the holotype) receiving an informal description. Other specimens of this species have been found from 2001 to 2002 including GGSr 001 (a well-preserved skull and partial skeleton) IVPP V 11860 (an isolated skull), IVPP V 12673 (a partial skeleton), and IVPP V 14372 (an isolated skull). IVPP V 12673 is the only well described specimen.<ref name="LJ13" />
''Xinpusaurus bamaolinensis'' was described in 2003 from SPCV 30015, a complete skeleton with a well-preserved skull and jaws found in two isolated slabs. These slabs may not represent the same individual, in which case only the front slab can be safely assigned to the genus.<ref name="LJ13" /> Inconsistencies within its description (such as reporting a [[Quadratojugal bone|quadratojugal]], a feature unknown in thalattosaurs) have led to some confusion over its diagnosis, and a redescription would be necessary to resolve these issues and determine if it is a valid species or not.<ref name=":0" />
''Xinpusaurus kohi'' was described in 2004 from GMPKU 2000/05, an incomplete skeleton. This specimen was also found in two slabs, with the rear slab missing most of the hindlimbs and possibly not belonging to the same individual as the first. In addition, there is evidence that some of the bone structure near the break has been tampered with and that most of the pelvic material has been lost. A 2013 analysis showed that many of the traits initially believed to differentiate ''X. kohi'' from ''X. suni'' were inaccurate, either due to incomplete data, misidentification, or poor preservation.<ref name="LJ13" /> However, a redescription in 2014 resurrected the legitimacy of the species. This redescription provided additional diagnostic features and argued that the alterations were relatively minimal and that the posterior slab was almost certainly from the same individual as the anterior one.<ref name=":0" />
''Xinpusaurus xingyiensis'' was described in 2016 from XNGM WS-53-R3, a nearly complete articulated skeleton from the Zhuganpo member of the Falang formation.
==Relationships==
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==References==
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{{Portal|Palaeontology}}
{{Thalattosauria|N.}}▼
{{Taxonbar|from=Q4021837}}
▲{{Thalattosauria}}
[[Category:Thalattosaurs]]
[[Category:Late Triassic reptiles of Asia]]
[[Category:Prehistoric reptile genera]]
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