Fossil Tortoise

Associated Smithsonian Expert: Hans-Dieter Sues, Ph.D.

Dr. Hans Sues holding the skull of a lion hunted by Theodore Roosevelt

Photo by Smithsonian

Dr. Hans Sues is a senior research geologist at the Smithsonian National Museum of Natural History who specializes in the study of dinosaurs and other vertebrates from the Mesozoic Era. He first became attracted to dinosaurs when he was four years old. After earning his doctorate from Harvard University, he worked as a postdoctoral fellow at McGill University and the National Museum of Natural History. Later Sues was curator and senior manager at the Royal Ontario Museum in Toronto and Carnegie Museum of Natural History in Pittsburgh before returning to the Smithsonian. He has collected fossil vertebrates across the United States as well as in Canada, China, Germany, and Morocco. Among his many discoveries are several new species of dinosaurs.

Meet our associated expert

This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.
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Fossil marine sea turtle, now extinct (Protostega gigas)
Photo by Chip Clark, Smithsonian, National Museum of Natural History

About Turtles (Order Testudines): Paleobiology

Turtles first appeared on Earth in the Triassic, before the rise of the dinosaurs. The earliest turtle found in the fossil record is an odd-looking animal called Odontochelys semitestacea, discovered in China and dated to about 220 million years old. It appeared to have lived in water and had just a bottom shell (“semi” = half; “stacea” =shelled). Unlike modern turtles, it had a jaw full of teeth. In contrast, another fossil turtle, Proganochelys, dated to a bit later, resembles a modern turtle with a full shell (although it did have a few teeth still, in the middle of its mouth). Paleontologists are not sure whether land turtles evolved from aquatic half-shelled turtles like Odontochelys, or whether Odontochelys evolved from full-shelled ancestors living on land. They are searching for an ancestor to both Odontochelys and Proganochelys to help solve this mystery.