This ‘grandfather’ turtle had no shell

Chuck Bednar for – @BednarChuck

The discovery of a 240-million-year-old reptile reveals that turtles and snakes are more closely related than scientists have previously believed, and may help explain how turtles first evolved their shells, according to a study published this week in the journal Nature.

The new extinct species, officially named Pappochelys rosinae, was found in a region that was once an ancient lake in southern Germany during the Middle Triassic Period, researchers from the Smithsonian Institute said in a statement. The creature’s physical characteristics revealed that it is “a clear intermediate between two of the earliest known turtles,” they added.

According to Discovery News, Pappochelys rosinae – which has also been affectionately dubbed the “Grandfather turtle” – was discovered by an international team of researchers. Based on its anatomy, the creature has been classified as a “diapsid” (a group also including dinosaurs, birds, pterosaurs, crocodiles, lizards, snakes, and other living and extinct species).

How the turtle got its shell

The Grandfather turtle was eight inches long, and while it did not have a fully developed shell, it did show signs of one, as it had broad, T-shaped ribs and a hard wall of bones around its belly. The configuration of the ribs, the authors explained, would have immobilized them and forced the creatures to develop a novel way of breathing.

“The mystery of how the turtle got its shell has been a long-standing question in evolutionary biology,” said study author Hans-Dieter Sues, curator of vertebrate paleontology in the Department of Paleobiology at the Smithsonian’s National Museum of Natural History. “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… but had never been observed in fossils – until now.”

Sues, along with Rainer Schoch, curator of fossil amphibians and reptiles at the State Museum of Natural History in Germany, led the team that analyzed the Grandfather turtle’s remains, along with more than a dozen other specimens collected from the same area. They focused their work on the morphological features that separated Pappochelys from its relatives.

The study authors also report that this new species of turtle, which is small enough to fit in the palm of a person’s hand, possesses an unusual pair of openings behind the eye socket on either side of the skull. This shows that turtles did not evolve from early stem-reptiles as previously thought, but were more closely related to snakes and other lizards, as modern turtles have lost these eye socket openings. The socket openings can still be found in present-day lizards and crocodilians, however.

“Scientists hypothesize that the development of the shell observed in early turtles supports the idea that the turtle shell evolved in aquatic environments rather than on land,” the Smithsonian said. “Early turtles may have relied on having a partially or fully fused plastron as a defense mechanism against these kinds of attacks. The back portion of the shell, called a carapace, appears later in the fossil record.”


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