‘Grandfather Turtle’ Forms Missing Link in Reptile Evolution

However, researchers suggest that the grandfather turtle was in the middle of an evolving state where soft backed animals transformed into hard shelled turtles we know of today.

Actually, researchers first found fossils of this 240-million year old animal in 2006 while excavating at Vellberg Lake, which is an ancient lakebed located in southeastern Germany. The species was a mutant combination of lizard and turtle features, particular seen in the skull for the latter.

The two distinctive holes on the side of the head behind each eye of Pappochelys provide vital clues to the evolutionary heritage of turtles, says Torsten Scheyer, a vertebrate paleontologist at the University of Zurich in Switzerland who was not involved in the work. Coincidentally, researchers studying turtle evolution have hypothesized that turtle ancestors once had riblike structures such as these, as well as protective bones on the shoulder girdle, Hans said.

But the early makings of a shell are visible in Pappocheyls’ skeleton. Its broad ribs have a T-shaped cross-section, but have yet to fuse into a true shell, and there are also clear beginnings of a bony plate protecting its underside.

Thanks to the newly discovered fossil of that little creature, scientists say they have solved the story of how the turtle got its shell.

Sues’s co-author, Rainer R. Schoch, a paleontologist at the Staatliches Museum für Naturkunde in Stuttgart, called Pappochelys a “transitional creature”, one that illustrates how ancient lizards became modern turtles.

It was only missing one thing: a shell. Pappochelys had thick abdominal bones, and some of them showed signs of fusing together at the ends.

And although the Pappochelys lived 10 million years before dinosaurs roamed, its freshwater lake habitat was not too safe. Early turtles like Pappochelys might have relied on having partially fused plastron on its stomach. By comparison, Odontochelys lived in present-day China 220 million years ago and has a fully developed plastron, a long tail and jaws with small teeth. So this is not the last piece of the turtle puzzle by far. In fact, experts classified it as “diapsid”, which is a group shared by animals such as dinosaurs, snakes, lizards, tuatara, crocodiles, birds and pterosaurs.

As for the rest of the reptile family, the German scientists explain that they didn’t develop shells of their own, simply because they had other needs in order to keep safe from their own predators in their own environment. But turtles are an outlier, the only modern reptile without these holes. “It shows that turtles are closely related to other modern reptiles and didn’t branch off early”.

DNA studies in recent years have had mixed results. Researchers had previously thought that turtles evolved from a different group of primitive reptiles that are now extinct.

Evidence from the 18 fossil skeletons of the species, allow researchers a picture of what Pappochelys may have looked like. Its ribs were broad and sturdy, but at the same time extended in line with the spine making the body hold more volume and improving buoyancy.


p style=”text-align: center;”>Artist's concept of the shell-less grandfather turtle


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