Eunotosaurus was a wide-bellied reptile with extremely broad ribs and eight dorsal vertebrae…which is how one could also describe a turtle. Several specimens are known. Smaller than a human hand, some were preserved curled up.
With Turtles. Then Not. Then With Again.
Watson (1914) originally considered Eunotosaurus a turtle ancestor.
Romer (1956) separated Eunotosaurus from turtles, with no other idea how Eunotosaurus nested.
Cox (1969) nested Eunotosaurus with Captorhinus and kin.
Cisneros et al. (2008) nested Eunotosaurus with Milleretta. (Bravo!!)
Currently Lyson et al. (2010) puts Eunotosaurus and turtles together again. Unfortunately the support values were chiefly below 0.66 and too few taxa were used compared to the large study found here. On the plus side, Eunotosaurus did nest with Acleistorhinus and Milleretta in that study.
Figure 1. Eunotosaurus and its sister taxa, Acleistorhinus and Milleretta RC14.
The Closest Sister Taxa to Eunotosaurus
Here, in the large study, Acleistorhinus was the closest sister taxon to Eunotosaurus (Figure 1). Unfortunately, only the skull is known. The next closest sister taxon was the RC14 specimen of Milleretta, which shares the expanded ribs that characterize Eunotosaurus. More Eunotosaurus details can be found at reptileevolution.com
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
Watson DMS 1914. Eunotosaurus africanus (Seeley) and the ancestors of the Chelonia, Proceedings of the Zooogical Society of London 11:1011–1020.
Cisneros JC, Rubidge BS, Mason R and Dube C 2008. Analysis of millerettid parareptile relationships in the light of new material of Broomia perplexa Watson, 1914, from the Permian of South Africa. Journal of Systematic Palaeontology 2008 (6): 453–462. doi:10.1017/S147720190800254X
Cox CB 1969. The problematic Permian reptile Eunotosaurus. Bulletin of the British Museum of Natural History 18: 167–196.
Keyser AW and Gow CE 1981. First complete skull of the Permian reptile
Eunotosaurus africanus Seeley. South African Journal of Science 77: 417–420.
Gow CE 1997. A reassessment of Eunotosaurus africanus Seeley (Amniota: Parareptilia). Palaeontologia Africana, 34:33–42.
Gow CE and de Klerk B 1997. First record of Eunotosaurus (Amniota: Parareptilia) from the Eastern Cape. Palaeontologia Africana, 34: 27–31.
Lyson TR, Bever GS, Bhullar B-AS, Joyce WG and Gauthier JA 2010. Transitional fossils and the origin of turtles. Proceedings of the Royal Society B Available online 9 June 2010: 830. online pdf
Modesto SP 2000. Eunotosaurus africanus and the Gondwanan ancestry of anapsid reptiles. Palaeontologia Africana, 36:15–20.
The Pterosaur Heresies 