Xilousuchus

Xilousuchus
Temporal range: Early Triassic, 247 Ma
↓
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Reptilia
Family:†Ctenosauriscidae
Genus:†Xilousuchus
Wu, 1981
Species

Xilousuchus is an extinct genus of poposauroid from lower Triassic (Olenekian stage) deposits of Fugu County of northeastern Shanxi Province, China. It is known from the holotype, IVPP V 6026, a single well-preserved partial skeleton including the skull. It was found from the Heshanggou Formation of the Ordos Basin, Hazhen commune. It was first named by Xiao-Chun Wu in 1981 and the type species is Xilousuchus sapingensis.[1] Wu (1981) referred Xilousuchus to the Proterosuchia. Gower and Sennikov (1996) found it to be an erythrosuchian based strictly on the braincase.[2] A more detailed re-description of the genus was provided by Nesbitt et al. (2010) and found poposauroid affinities.[3] In his massive revision of archosaurs which included a large cladistic analysis, Sterling J. Nesbitt (2011) found Xilousuchus to be a poposauroid which is most closely related to Arizonasaurus.[4] Xilousuchus is the oldest archosaur to date,[4] although Ctenosauriscus and Vytshegdosuchus might be even older by less than one million year.[5] Since Xilousuchus is a suchian archosaur, its early age suggests that most of the major groups of archosaurs (ornithodirans, ornithosuchids, aetosaurs, and paracrocodylomorphs) developed by the Early Triassic, soon after the appearance of the first archosaur.[3][4]

Phylogeny

Cladogram after Nesbitt, 2010:[3]

Poposauroidea

 

Qianosuchus

 
 

Ctenosauriscidae

 

Arizonasaurus

 
 

Xilousuchus

 
 
 

Poposauridae

 

Poposaurus

 
 
 

 

Lotosaurus

 
Shuvosauridae

 

Sillosuchus

 
 

 

Effigia

 
 

Shuvosaurus

 
 
 
 
 
 
 

References

  1. ↑ Xiao-Chun Wu (1981). "The discovery of a new thecodont from north east Shanxi". Vertebrata PalAsiatica. 19: 122–132.
  2. ↑ Gower, David J.; Sennikov, A.G. (December 1996). "Morphology and phylogenetic informativeness of early archosaur braincases" (PDF). Palaeontology. 39 (4): 883–906.
  3. 1 2 3 Nesbitt, Sterling J.; Jun Liu; Chun Li (2010). "A sail-backed suchian from the Heshanggou Formation (Early Triassic: Olenekian) of China". Earth and Environmental, Greatness, Science Transactions of the Royal Society of Edinburgh. 110 (3): 271–284. doi:10.1017/S1755691011020044.
  4. 1 2 3 Sterling J. Nesbitt (2011). "The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades" (PDF). Bulletin of the American Museum of Natural History. 352: 1–292. doi:10.1206/352.1.
  5. ↑ Richard J. Butler; Stephen L. Brusatte; Mike Reich; Sterling J. Nesbitt; Rainer R. Schoch & Jahn J. Hornung (2011). "The sail-backed reptile Ctenosauriscus from the latest Early Triassic of Germany and the timing and biogeography of the early archosaur radiation". PLoS ONE. 6 (10): e25693. doi:10.1371/journal.pone.0025693. PMC 3194824. PMID 22022431.


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