Fossil of Missing Link in Turtle Evolution Discovered
Posted on June 25, 2015
Scientists have discovered the fossil of an ancient reptile that is considered a key link in turtle evolution. The fossil was found in an area that was an ancient lake in southern Germany 240 million years ago during the Middle Triassic Period. The ancient reptile, Pappochelys, lacked a shell but did have fused rod-like bones in its belly.
The ancient turtle study was conducted by Hans-Dieter Sues, curator of vertebrate paleontology in the Department of Paleobiology at the Smithsonian's National Museum of Natural History, and Rainer Schoch, curator of fossil amphibians and reptiles at the State Museum of Natural History in Stuttgart, Germany. The researchers say the physical traits of Pappochelys make it a clear that it is an intermediate link between two of the earliest known turtles, Eunotosaurus and Odontochelys.
The rod-like bones protecting Pappochelys are the beginnings of what eventually evolved into a turtle shell. The belly portion of a turtle shell is called the plastron. The researchers say the Pappochelys fossil indicates that the plastron formed through the fusion of rib-like structures and parts of the shoulder girdle.
Sues says in a statement, "The mystery of how the turtle got its shell has been a long-standing question in evolutionary biology. In the case of Pappochelys, we see that its belly was protected by an array of rod-like bones, some of which are already fused to each other. Such a stage in the evolution of the turtle shell had long been predicted by embryological research on present-day turtles but had never been observed in fossils-until now."
Pappochelys was small and could have fit in the palm of a human hand. It reached about 8 inches in length. The turtle ancestor lived in a tropical environment in what is now southern Germany. It likely fed on insects and worms. A reconstructed skeleton of Pappochelys is pictured above with its ribs shown in black.
A research paper on Pappochelys is published here in the journal, Nature.