Here's how the turtle got its shell

For at least a century, scientists have puzzled over the turtle. Thanks to a gap in the fossil record between 260 million and 220 million years ago, it's unclear how the turtle got its shell and to whom it's most closely related.

Now a fossil from 240 million years ago, found at a quarry in Germany, fills in some missing links—including that turtles appear more closely related to snakes and lizards than crocodiles and birds, researchers report in the journal Nature.

Dubbed "grandfather turtle," the remains of Pappochelys rosinae reveal a shell-less 8-inch reptile whose tail accounted for half its total length, reports Discovery. P. rosinae did have the makings of a shell, with T-shaped ribs and hard webbing along its belly.

(Full shells didn't appear until around 214 million years ago, reports Discover, perhaps when the turtle's ancestors were water-dwelling and needed to protect their major organs as well as control buoyancy.) The grandfather turtle's skull also resembles snake and lizard skulls more than archosaurs, a group that includes crocodiles and birds.

But the mystery persists: In spite of this latest anatomical evidence, one researcher admits that "molecular data places turtles closer to crocodylians and birds." (This turtle is near extinction.)

This article originally appeared on Newser: How the Turtle Got Its Shell

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