When it comes to animals with iconic functions, the turtle is high on the list. Deer have horns, kangaroos have pouches, people have existential fear and turtles have shells … right? Apparently this was not always the case, because a new set of fossils from China reveals that some old turtles never bothered to grow a shell.
In a new article published in Nature, researchers describe the discovery of an early turtle species Eorhynchochelys sinensis. Nicknamed the "dageradelppad," the animals lived around 228 million years ago, and they were massive in size. Measuring more than six feet tall would have been an intimidating sight, and his hardened beak and flat body match what we think of a turtle. Everything corresponds except the scale.
Scientists believe that the essence of the water was what it was looking for, but it has never developed the hard outer layer that most modern turtles share. This is particularly curious because the body of the animals, which was large, flat and soft, would have benefited severely from a hard cover.
"This being was more than two meters long, it had a strange disk-like body and a long tail, and the front part of its jaw developed into this strange beak," co-author Olivier Rieppel of Chicago's Field Museum notes. "It probably lived in shallow water and dug in the mud as food."
Interestingly, other early fossils of different turtles had shells but no jaws with a beak. The common-day turtle had a beak but no scale, but modern turtles have all of the above. This strongly suggests that the evolution of the species we see today on earth is probably much more complicated than someone realizes.
"This impressively large fossil is a very exciting discovery that gives us another piece in the puzzle of the evolution of the turtle," explains Nick Fraser, lead author of the new work. "It shows that the early evolution of turtles was not a simple, step-by-step succession of unique traits, but was a much more complex series of events that we are just beginning to unravel."