It was a creature that one scientist said resembled "a strange, gluttonous lizard that swallowed a small Frisbee."

But a sophisticated skull analysis showed that this reptile called Eunotosaurus africanus that lived in southern Africa 260 million years ago is actually the earliest-known turtle, even though it had no shell.

Eunotosaurus, about a foot (30 cm) long, possessed wide and flat ribs that gave it a distinctly rounded and turtle-like profile. It mixed features of its lizardlike ancestors with emerging turtle-like characteristics that evolved over tens of millions of years into familiar turtle traits, researchers said.