First turtles had no carapace

The oldest specimen of turtle, that scientists found in China and discovered Tuesday that 220 million years, shows that the shells of these animals have developed from the extension of the spine and enlargement of the ribs

'Odontochelys semistestacea' lived in the water

How does the turtle developed its carapace? This was a question that the scientists placed hundreds of years, but now it finally has the answer. The discovery in China of three fossils of a new species of turtle, with 220 million years, shows that in the beginning, these animals developed the plastron (the lower part of the carapace) from the expansion of the spine and enlargement of ribs.

Until now there were two theories to explain the formation of the carapace. One said that it had developed from skeletal plates in the skin, such as that some dinosaurs had and still have crocodiles. But the way the embryo grows inside the turtle eggs seemed to contradict this theory. The studies in this area showed that the shell grows from the bottom up, and the expansion of the spine, with the ribs to extend up to form a protective shell.

"With the Odontochelys semistestacea, we now have clear fossil evidence of this process in an adult," said paleontologist Chinese Xiao-Chun Wu, the Natural Museum of Canada, lead author of the study which is published today in the journal Nature. The researchers, from Canada, China and U.S., also concluded that the turtle was an aquatic animal and not land, as other fossil seemed to indicate. The cravat served to protect the turtle from their predators, while swimming.

Before the discovery of Odontochelys semistestacea, which literally means turtle carapace and half with teeth (something too rare), the oldest specimen was Proganochelys, with 210 million years old, found in Germany. However, this had to shell fully formed, so the scientists could not explain how it developed.