The findings are “a very important contribution in addressing who turtles are related to, as well as the evolutionary origin of the turtle shell,” says Tyler Lyson, a vertebrate paleontologist at the Denver Museum of Nature & Science who was not involved with the study. “These have been two vexing questions for evolutionary biologists for the last 200 years.”

About two dozen or so fossils of the creature have been recovered, all of them from 240-million-year-old rocks deposited as sediment on the floor of a shallow, 5-kilometer-long lake in what is now southern Germany. Most of the remains include only bits of bone and are from individuals of various sizes, says Hans-Dieter Sues, a vertebrate paleontologist at the Smithsonian Institution's National Museum of Natural History in Washington, D.C. But between the two most complete specimens yet found, he and Rainer Schoch, a paleontologist at the State Museum of Natural History Stuttgart in Germany, have put together a full skeleton and most of a skull.