The tortoise shell - an amazing story of evolution.

An early fossil of a tortoise that lived in South AFrican 260 years ago has been discovered. It has no shell though it shares other anatomical features with modern tortoises.  About 50 million years later fossils of tortoises with shells start to appear.
Dr Tyler Lyson of Wits University's Evolutionary Studies Institute, the Smithsonian Institution and the Denver Museum of Nature and Science explained: "Tortoises have a bizarre body plan and one of the more puzzling aspects to this body plan is the fact that tortoises have locked their ribs up into the iconic tortoise shell. No other animal does this and the likely reason is that ribs play such an important role in breathing in most animals including mammals, birds, crocodilians, and lizards."
Dr Lyson and his colleagues have shown that the modern tortoise breathing apparatus was already in place in the earliest fossil tortoise, an animal known as Eunotosaurus africanus.
This new species bridges the gap between the earliest proto tortises and the hard shelled tortoise of modern times.

This is how the hard carapice of the tortoise developed over the years. Watch the video here.

Download and read the scientific paper here: Tyler R. Lyson, Emma R. Schachner, Jennifer Botha-Brink, Torsten M. Scheyer, Markus Lambertz, G. S. Bever, Bruce S. Rubidge, Kevin de Queiroz. Origin of the unique ventilatory apparatus of turtles. Nature Communications, 2014; 5: 5211 DOI: 10.1038/ncomms6211
Or there is an easier version here.
If you have a tortoise or a snake or a lizard, do my Reptile relationships survey at  https://www.surveymonkey.co.uk/r/FGJZKLT 
and pass it on to others.