Xinpusaurus
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Xinpusaurus Temporal range: Late Triassic, Carnian |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | †Thalattosauria |
| Superfamily: | †Thalattosauroidea |
| Genus: |
†Xinpusaurus Yin, 2000 |
| Species | |
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Xinpusaurus is an extinct genus of thalattosaur from the Late Triassic of Guanling in Guizhou, China. Several species have been named since 2000: the type species X. suni along with the species X. bamaolinensis and X. kohi. A 2013 study proposed that all three species are synonymous with each other, in which case X. suni would be the only valid species, although a 2014 study argued that X. kohi was also valid.A fourth species, X. xinyiensis, was described in 2016.
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 premaxillae. Xinpusaurus had a short neck, a massive quadrate, and one of the few braincases preserved in thalattosaurs. The lower jaws of this genus show two different forms of dentary-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's suture differs between specimens while X. xinyiensis seems to have a type 2 suture. 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.This genus also has a uniquely upward-curving maxilla, a wide proximal end of the humerus, and a radius with a convex lateral edge and concave medial edge.
X. bamaolinensis and X. kohi had particularly elongated premaxillae, forming a narrow and pointed rostrum. However, it should be noted that 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.
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