Eunotosaurus

Name: Eunotosaurus‭ (‬original noded lizard‭)‬.
Phonetic: Yew-no-to-sore-us.
Named By: Seeley‭ ‬-‭ ‬1892.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Sauropsida,‭ ‬Parareptilia,‭ ‬Millerettidae.
Species: E.‭ ‬africanus‭ (‬type‭)‬.
Diet: Herbivore.
Size: 30‭ ‬centimetres long.
Known locations: South Africa.
Time period: Wuchiapingian of the Permian.
Fossil representation: Several individual specimens.

       Eunotosaurus was long considered the ancestor to turtles.‭ ‬This theory came from the specially enlarged and curved vertebrae and ribs that balloon outwards that would have created the appearance of a skin covered shell.‭ ‬It is now thought however that the vertebrae and rib adaptation of Eunotosaurus and the evolution of turtles are a case of convergent evolution.‭ ‬This is where two animals form a similar evolutionary adaption,‭ ‬even though they are not of the same animal group,‭ ‬or direct descendent or ancestor to one another.
       The vertebrae of Eunotosaurus are very similar to turtles in both structure and number.‭ ‬The ribs are also broad to the point that they make contact with one another,‭ ‬a feature also seen in turtles.‭ ‬The key difference is that the pelvis of Eunotosaurus is placed behind the specially adapted vertebrae and ribs.‭ ‬In contrast,‭ ‬the pelvis of turtles is covered so that it can be protected by the shell.‭
       The rib adaptations would have given Eunotosaurus better protection from predators,‭ ‬but exactly how remains unclear.‭ ‬The enlarged cross section would have made it difficult for some predators to swallow Eunotosaurus whole.‭ ‬The ribs would have also provided protection from the same predators that did not have the strength to bite through them.‭ ‬However,‭ ‬these ribs were not formed to provide protection for the head,‭ ‬limbs or tail.‭ ‬At best this adaptation would only reduce the number of predators able to eat Eunotosaurus,‭ ‬but that may have been enough for the species to survive for a time.

Further reading
- On a New Reptile from Welte Vreden (Beaufort West), Eunotosaurus africanus (Seeley). - Quarterly Journal of the Geological Society of London 48:583-585. - H. G. Seeley - 1892.
- Eunotosaurus africanus Seeley and the ancestors of the Chelonia. - Proceedings of the Zoological Society of London 11: 1011–1020. - D. M. S. Watson - 1914.
- The problematic Permian reptile Eunotosaurus. - Bulletin of the British Museum (Natural History), Geology Series 18 (5): 167–196. - C. B. Cox - 1969.
- Eunotosaurus africanus from the Ecca–Beaufort contact in Northern Cape Province, South Africa — implications for Karoo Basin development. - South African Journal of Science 95: 553–555. - B. S. Rubidge, S. Modesto, C. Sidor & J. Welman - 1999.
- Eunotosaurus africanus and the Gondwanan ancestry of anapsid reptiles. - Palaeontologia Africana 36: 15–20. - S. P. Modesto - 2000.



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