A Middle Triassic stem-turtle and the evolution of the turtle body plan

A new stem-turtle, Pappochelys rosinae, is structurally and chronologically intermediate between the stem-turtles Eunotosaurus and Odontochelys and is from the late Middle Triassic of Germany (Ladinian; ∼240 million years ago). The three taxa share anteroposteriorly broad trunk ribs that are T-shaped in cross-section and bear sculpturing, elongate dorsal vertebrae, and modified limb girdles. Pappochelys closely resembles Odontochelys in various features of the limb girdles. Unlike Odontochelys, it has a cuirass of robust paired gastralia in place of a plastron. Pappochelys provides new evidence that the plastron partly formed through serial fusion of gastralia. The skull of Pappochelys has small upper and ventrally open lower temporal fenestrae, supporting the hypothesis of diapsid affinities of turtles.


Life reconstruction: