Science, Tech, Math › Animals & Nature Profile of the Prehistoric Archelon Share Flipboard Email Print SCIEPRO/SCIENCE PHOTO LIBRARY/Getty Images Animals & Nature Dinosaurs Marine Reptiles Basics Paleontologists Carnivores Dinosaurs & Birds Herbivores Prehistoric Mammals Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Insects Marine Life Forestry Evolution View More By Bob Strauss Science Writer B.S., Cornell University Bob Strauss is a science writer and the author of several books, including "The Big Book of What, How and Why" and "A Field Guide to the Dinosaurs of North America." our editorial process Bob Strauss Updated January 16, 2020 Name: Archelon (Greek for "ruling turtle"); pronounced ARE-kell-onHabitat: Oceans of North AmericaHistorical Period: Late Cretaceous (75 to 65 million years ago)Size and Weight: About 12 feet long and two tonsDiet: Squids and jellyfishDistinguishing Characteristics: Leathery shell; wide, paddlelike legs About Archelon Dinosaurs weren't the only animals that grew to immense sizes during the late Cretaceous period. At a whopping 12 feet long and two tons, Archelon was the one of the largest prehistoric turtles that ever lived (it used to be on top of the charts until the discovery of the truly stupendous Stupendemys of South America), about the size (and shape, and weight) of a classic Volkswagen Beetle. By comparison with this North American behemoth, the largest Galapagos tortoises alive today weigh a little over a quarter of a ton and measure about four feet long! (The closest living relative of Archelon, the Leatherback, comes much closer in size, some adults of this seagoing turtle weighing close to 1,000 pounds.) Archelon differed significantly from modern turtles in two ways. First, its shell wasn't hard, but leathery in texture, and supported by an elaborate skeletal framework underneath; and second, this turtle possessed unusually wide, flipper-like arms and legs, with which it propelled itself through the shallow Western Interior Sea that covered much of North America about 75 million years ago. Like modern turtles, Archelon had a human-like life span as well as a nasty bite, which would have come in handy when tussling with the giant squids that constituted the bulk of its diet. One specimen on display in Vienna is thought to have lived for over 100 years, and probably would have survived much longer if it hadn't asphyxiated on the seafloor. Why did Archelon grow to such an enormous size? Well, at the time this prehistoric turtle lived, the Western Interior Sea was well-stocked with the vicious marine reptiles known as mosasaurs (a good example being the contemporary Tylosaurus), some of which measured over 20 feet long and weighed four or five tons. Clearly, a speedy, two-ton marine turtle would have been a less appetizing prospect to hungry predators than smaller, more pliable fish and squids, though it's not inconceivable that Archelon occasionally found itself on the wrong side of the food chain (if not by a hungry mosasaur, then perhaps by a plus-sized prehistoric shark-like Cretoxyrhina).