Anapsida: Eunotosaurus

Taxa on This Page

1. Eunotosaurus X

Life restoration of Eunotosaurus africanus. illustration by Smokeybjb (Wikipedia)

Descriptions

Eunotosaurus africanus Seeley, 1892

Comments: A Tapincopehalus Assemblage Zone index fossil (Rubidgeetal99). Once considered the ancestor of the Chelonia, it is now known that this small animal independently evolved turtle like characteristics. The semi-rigid, turtle-like ribcage implies a tortoise-like fashion of walking (Sumida & Modesto) . Beyond being a member of the anapsida, evolutionary relationships were for a long time uncertain, which is not surprsiing for a highly derived taxon (the same thing is the case with Mesosaurus). But recent cladistic studies (Müller & Tsuji 2007, Cisneros et al 2008) show Eunotosaurus to be be a Millerettid. More unexpected (and unlikely?) is the study by Lyson et al 2010 that even restores the chelonian ancestor hypothesis. One problem here is that Eunotosaurus is too early to be a good ancestor, some 45 million years separate it from Odontochelys, the oldest known turtle (there's a similar problem with the time difference between "Protoavis" and Archaeopteryx; a major adaptive radiation such as birds, turtles, or placental mammals would be expected to be immediately evident in the fossil record) MAK120324

Links: Eunotosaurus And Turtle Evolution - All About Reptiles Eunotosaurus - Wikipedia