Cleaning up mistakes – Sinosaurosphargis now nests (almost) in the Enaliosauria

Sinosaurosphargis.

Figure 1. Sinosaurosphargis. Click for more information. Like other enaliosaurs, the naris is high, the humerus is bent and the transverse processes  are elongated, anchors for laterally-directed ribs beneath a turtle-like shell.

Sinosaurosphargis, and its sister, Largocephalosaurus, are two more turtle-like forms I earlier nested with basal enaliosaurs, close to Claudiosaurus. That was correct. Nestings with basal placodonts were incorrect. Largocephalosaurus is better known now.

This nesting means the shell of Sinosaurosphargis was derived independently, convergent with those of turtles, Henodus and Cyamodus. None of these are homologous structures! Thankfully PAUP can see through such convergence.

Since the outgroups of Sinosaurosphargis are all slender carnivorous or piscivorous speedsters we should expect to see more variation in this already very wide radiation at the moment these reptiles returned to the water. When the differences are this great, the number of intervening or transitional taxa is great, all undiscovered at this point. Look for more basal enaliosaurs to fill this gap, probably buried along with the sediments of the ancient Tethys Sea.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Li C, Rieppel O, Wu X-C, Zhao L-J and Wang LT 2011. A new Triassic marine reptile from southwestern China. Journal of Vertebrate Paleontology 31 (2): 303-312. doi:10.1080/02724634.2011.550368.
Cheng L, Chen X-H, Zeng X-W and Ca Y-J 2012. A new eosauropterygian (Diapsida: Sauropterygia) from the Middle Triassic of Luoping, Yunnan Province. Journal of Earth Science 23 (1): 33-40.

wiki/Sinosaurosphargis

wiki/Largocephalosaurus

 

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