Learn how a 260-million-year-old Permian reptile, once thought to explain turtle evolution, turned out to belong to a different lineage, reshaping the story of turtle origins in the Triassic Period.
Eunotosaurus africanus seemed to capture an early stage in turtle evolution. It had wide, flattened ribs, a shortened trunk, and a body that, to generations of paleontologists, looked unmistakably like a shell in the making.
For nearly two decades, the 260-million-year-old reptile sat near the base of the turtle family tree, offering one of the earliest clues to how turtles began evolving their shells. Then, a team of researchers looked inside its skull.
In a new study published in Current Biology, researchers used CT scanning to examine the internal anatomy of Eunotosaurus in new detail. The scans suggest the animal was not an early turtle at all, but a member of a separate extinct reptile lineage that independently evolved a turtle-like body.
The finding removes a source of confusion from the turtle family tree and helps bring fossil evidence in line with DNA studies showing that turtles are closely related to archosaurs, the reptile group that includes crocodiles, birds, dinosaurs, and pterosaurs.
Instead, the scans showed a close match with millerettids, a group of extinct stem reptiles from the Permian Period. Milleretta rubidgei, one member of that group, shared 12 anatomical features with Eunotosaurus, including broad, overlapping ribs and a shortened trunk...