9 Extinct Exotic Sea Creatures

This drawing shows an artist's impression of the Archelon turtle; the Stupendemys is thought to be even bigger. MR1805/iStock/Thinkstock

Ex-professional basketball player Shaquille O'Neal is a humongous man. At 7 feet 1 inch (2.2 meters) and 325 pounds (147 kilograms), he's the type of guy who has to duck into doorways, has trouble getting into European cars and should probably buy two seats if his private jet is in the shop and he has to fly coach [source: ESPN]. Consider the Stupendemys the Shaq of the turtle world.

This gigantic sea turtle called the rivers and lakes of South America home as recently as about 5 or 6 million years ago. Its name means "astonishing turtle" for good reason: The Stupendemys shell often stretched more than 7 feet (1.8 meters) in length and another 7 feet in width. That's good enough to probably make it the world's largest turtle, perhaps even bigger than the mammoth Archelon from the late Cretaceous period 65 million years ago. The Stupendemys' neck was so long, it had to fold it to one side to fit it in the shell. It's believed that the turtle grew in size over time in response to the gargantuan beasts with whom the Stupendemys shared living spaces, including various types of large crocodile [sources: Prehistoric Wildlife, McCormick].