Picture of a protostega

At more than ten feet (three meters) long, Protostega were among the largest turtles to ever live. Despite their size, they were excellent swimmers.

Copyright © MMVII NGHT, Inc.

Fast Facts

Length, 10 ft (3 m)
Did you know?
Many Protostega specimens lack limbs and skulls, suggesting that their remains were scavenged by sharks and other predators.
Size relative to a 6-ft (2-m) man

Please add a "relative" entry to your dictionary.

Growing more than 10 feet (3 meters) long, Protostega was among the largest turtles to ever live. Unlike most turtles, whose shells are made of expanded and fused bones that form a relatively solid dome, widely spaced bones that looked more like the rafters of a roof held up Protostega's leathery shell. Though the shell design provided less protection, the lighter load combined with powerful, flipper-like front legs made Protostega a strong, inexhaustible swimmer. Females likely migrated hundreds of miles to lay eggs on sandy beaches, much like sea turtles do today.

Movement onshore, however, was difficult. An adult female Protostega may have weighed a ton or more, a hefty load to drag out of the ocean to lay eggs. But lay eggs on the beach they did by the dozens, a reproductive strategy of safety in numbers that helped at least a few survive to adulthood. In fact, marine turtles were the only seagoing reptiles to escape extinction at the end of the Cretaceous, 65 million years ago.

A large and pointed head with a sharp beak and strong jaws probably helped the ancient turtles feed on slow-moving marine creatures such as jellyfish and shellfish as well as seaweed and floating carcasses—much as their descendents do today. Shark teeth embedded in Protostega bones housed at a museum in Chicago suggest the turtles were sometimes a meal themselves.

Prehistoric Features

  • Picture of carnotaurus

    Bizarre Dinosaurs

    A bizarre gallery of Mesozoic monsters prompts John Updike to ask: What has evolution wrought?

  • Picture of dimorphodon flying across the forest in a scene from the movie Flying Monsters 3D

    Flying Monsters 3D

    Could flying monsters have existed? With cutting-edge 3-D filming technology and CGI, Flying Monsters 3D recreates spectacular pterosaurs and brings these giant flying creatures to life.

  • Picture of dinosaurs during the Jurassic era

    Prehistoric World

    Discover and explore prehistoric times with galleries, time lines, quizzes, and more.

  • Picture of a theoretical scene of the mass extinction of dinosaurs

    Mass Extinctions

    More than 90 percent of all organisms that have ever lived on Earth are extinct. Learn how millions of creatures can disappear in a geological blink of an eye—and see what might be next.

Animals A-Z