Published: August 22, 2018

This Turtle Had No Shell, but the First Toothless Beak

Though it sounds a little awkward, this newly discovered species fills a gap in the turtle family tree.

Illustration of a large, shell-less turtle with a rounded body and long tail, swimming underwater. The sea floor appears rocky, with some grasses.

You might recognize a turtle by its shell, but that wasn’t always the case—not all early turtles had shells. Another key turtle trait to look for is a toothless beak. A team of scientists, including Field paleontologist Olivier Rieppel, are learning more about how turtles developed their trademark features thanks to the discovery of a species that lived 228 million years ago.

This shell-less early turtle—Eorhynchochelys sinensis—was over six feet long with a Frisbee-shaped body and a long tail. It wasn’t particularly turtle-like in appearance by today’s standards, with wide ribs that didn’t yet form a shell. But it’s the earliest turtle we’ve seen with that toothless beak.

A fossil of a turtle skeleton with a rounded midsection and long, curved tail. The fossil is seen embedded in cracked gray rock.

Eorhynchochelys fossil at National Museums Scotland.

Nick Fraser

Its name helps tell the story: Eorhynchochelys (“Ay-oh-rink-oh-keel-is”) means “dawn beak turtle”—essentially, first turtle with a beak—while sinensis, meaning “from China,” refers to the place where paleontologist Li Chun discovered it.

Before finding Eorhynchochelys, scientists already knew about another early turtle: one with a partial shell but no beak. Until now, it’s been unclear how they all fit into the reptile family tree. Rieppel says that the origin of turtles was a mystery for years—and now Eorhynchochelys makes the picture of turtle evolution much clearer.

Illustration of an underwater scene with a striped, shell-less turtle with open mouth walking on a lush green seafloor. A second turtle swims in the background, and a fish swims off to the left.

Eorhynchochelys likely lived in shallow water and dug for food in the mud.

Institute of Vertebrate Paleontology and Paleoanthropology

The fact that Eorhynchochelys developed a beak before other early turtles but didn’t have a shell is evidence of mosaic evolution—the idea that traits can evolve independently from each other and at a different rate, and that not every ancestral species has the same combination of these traits. Modern turtles have both shells and beaks, but the path evolution took to get there wasn’t a straight line. Some turtle relatives got partial shells while others got beaks, and eventually, the genetic mutations that create these traits occurred in the same animal.

The full research paper is published in Nature. Institute of Vertebrate Paleontology and Paleoanthropology, the CAS Center for Excellence in Life and Paleoenvironment, National Museums Scotland, the Field Museum, and the Canadian Museum of Nature contributed to this study.