Xilousuchus
Xilousuchus | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Clade: | Archosauria |
Clade: | Pseudosuchia |
Clade: | †Poposauroidea |
Family: | †Ctenosauriscidae |
Genus: | †Xilousuchus Wu, 1981 |
Species: | †X. sapingensis
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Binomial name | |
†Xilousuchus sapingensis Wu, 1981
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Xilousuchus is an
Features
Xilousuchus was probably quite a large animal when alive, possibly between three and four metres long. It had a small head, and a sail along its neck and back. It probably had long and quite powerful legs, and would have been an active hunter. Only the partial skull, cervical vertebrae, and a few other fragments are preserved.[3]
Xilousuchus has a relatively small head and long neck, with a skull length of approximately 25 cm and neck of 45 cm. The skull is fragmentary, but much of the snout and maxilla are present. Only one maxillary tooth has been fossilised. The maxilla has a partially developed palatal process, and the angle of the dorsal process indicates that Xilousuchus had a large antorbital fenestra. The single preserved maxillary tooth is large, almost 15 mm long, and in other dental alveoli where the teeth are missing replacement teeth are sometimes visible, indicating that it was a polyphyodont. The tooth has small serrations, is curved backwards, and is laterally compressed, indicating that it could have punctured flesh or possibly sliced off chunks. The lacrimal and nasal bones are large but quite thin and fragile. The skull has a reasonably well-preserved braincase with thick walls and a small volume, and this shows that the brain was not large. It closely resembles that of Arizonasaurus, indicating that the two species are close relatives. The dentary bone is partially preserved for both left and right, and would have held thirteen teeth on each side, although only the nutrient foramina remain. Like that of most archosaurs from the Triassic, the dentary is unspecialised.[3]
The cervical vertebrae have large, flattened
One sacral vertebra is present, and it shows a clear suture where it was joined to the sacral ribs and pelvis. The orientation of the sacral rib suggests that the ilium was downturned, although this is not certain. Two caudal vertebrae are present as well, and these are poorly preserved with missing neural spines, but show facets where chevrons would have been attached. The proximal ends of two cervical ribs have also been fossilised, and these have two heads - a tuberculum and capitulum. They are slender, unlike those of phytosaurs and crocodylomorphs. One clavicle and one ungual are also known, but it is not known where the ungual is from. They have few distinguishing features and resemble those of other ctenosauriscids very closely.[3]
Phylogeny
Cladogram after Nesbitt, 2010:[3]
References
- ^ Xiao-Chun Wu (1981). "The discovery of a new thecodont from north east Shanxi". Vertebrata PalAsiatica. 19: 122–132.
- ^ Gower, David J.; Sennikov, A.G. (December 1996). "Morphology and phylogenetic informativeness of early archosaur braincases" (PDF). Palaeontology. 39 (4): 883–906.
- ^ S2CID 130449116.
- ^ S2CID 83493714.
- PMID 22022431.