Science, Tech, Math › Animals & Nature The Dinosaurs and Prehistoric Animals of North Dakota Share Flipboard Email Print Animals & Nature Dinosaurs Basics Paleontologists Carnivores Dinosaurs & Birds Herbivores Marine Reptiles 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 April 20, 2017 01 of 08 Which Dinosaurs and Prehistoric Animals Lived in North Dakota? Brontotherium, a prehistoric mammal of North Dakota. Wikimedia Commons Disappointingly, considering its proximity to dinosaur-rich states like Montana and South Dakota, very few intact dinosaurs have ever been discovered in North Dakota, Triceratops being the only notable exception. Even still, this state is famous for its wide variety of marine reptiles, megafauna mammals and prehistoric birds, as you can learn about by perusing the following slides. (See a list of dinosaurs and prehistoric animals discovered in each U.S. state.) 02 of 08 Triceratops Triceratops, a dinosaur of North Dakota. Wikimedia Commons One of the most famous residents of North Dakota is Bob the Triceratops: a nearly intact specimen, 65 million years old, discovered in North Dakota's portion of the Hell Creek formation. Triceratops wasn't the only dinosaur that lived in this state during the late Cretaceous period, but it was the one that has left the most complete skeleton; more fragmentary remains also point to the existence of Tyrannosaurus Rex, Edmontonia, and Edmontosaurus. 03 of 08 Plioplatecarpus Plioplatecarpus, a marine reptile of North Dakota. Wikimedia Commons Part of the reason that so few dinosaurs have been discovered in North Dakota is that, during the late Cretaceous period, much of this state was submerged under water. That explains the discovery, in 1995, of the nearly complete skull of Plioplatecarpus, an especially fierce type of marine reptile known as a mosasaur. This North Dakota specimen measured a scary 23 feet from head to tail, and was clearly one of the apex predators of its undersea ecosystem. 04 of 08 Champsosaurus Champsosaurus, a prehistoric reptile of North Dakota. Minnesota Science Museum One of the most common fossil animals of North Dakota, represented by numerous intact skeletons, Champsosaurus was a late Cretaceous reptile that closely resembled a crocodile (but belonged, in fact, to an obscure family of creatures known as choristoderans). Like crocodiles, Champsosaurus prowled the ponds and lakes of North Dakota in search of tasty prehistoric fish. Oddly enough, only female Champsosaurus were capable of climbing onto dry land, in order to lay their eggs. 05 of 08 Hesperornis Hesperornis, a prehistoric bird of North Dakota. Wikimedia Commons North Dakota isn't generally known for its prehistoric birds, which is why it's remarkable that a specimen of the late Cretaceous Hesperornis has been discovered in this state. The flightless Hesperornis is believed to have evolved from earlier flying ancestors, much like modern ostriches and penguins. (Hesperornis was one of the instigators of the Bone Wars, the late 19th-century rivalry between paleontologists Othniel C. Marsh and Edward Drinker Cope; in 1873, Marsh accused Cope of stealing a crate of Hesperornis bones!) 06 of 08 Mammoths and Mastodons The Woolly Mammoth, a prehistoric mammal of North Dakota. Wikimedia Commons Mammoths and Mastodons roamed the northernmost reaches of North America during the Pleistocene epoch--and what part of the continental U.S. is located further north than North Dakota? Not only has this state yielded the remains of Mammuthus primigenius (the Woolly Mammoth) and Mammut americanum (the American Mastodon), but fossils of the distant elephant ancestor Amebelodon have been discovered here as well, dating to the late Miocene epoch. 07 of 08 Brontotherium Brontotherium, a prehistoric mammal of North Dakota. Nobu Tamura Brontotherium, the "thunder beast"--which has also gone by the names Brontops, Megacerops and Titanops--was one of the largest megafauna mammals of the late Eocene epoch, distantly ancestral to modern horses and other odd-toed ungulates (but not so much to rhinoceroses, which it vaguely resembled, thanks to the prominent horns on its snout). The lower jawbone of this two-ton beast was discovered in North Dakota's Chadron Formation, in the central part of the state. 08 of 08 Megalonyx Megalonyx, a prehistoric mammal of North Dakota. Wikimedia Commons Megalonyx, the Giant Ground Sloth, is famous for having been described by Thomas Jefferson, a few years before he became the third president of the United States. Somewhat surprisingly for a genus whose remains are usually discovered in the deep south, a Megalonyx claw was recently unearthed in North Dakota, proof that this megafauna mammal had a wider range than was previously believed during the late Pleistocene epoch.