South Dakota is famous for its profusion of dinosaurs, but this state was also home to some very big prehistoric mammals and turtles, as listed below. (See an interactive map of dinosaurs and prehistoric animals in the United States.)
Greek for "giant duck," Anatotitan was a five-ton hadrosaur, or duck-billed dinosaur, of the late Cretaceous period, characterized by (you guessed it) its broad, ducklike bill. This strange dinosaur was discovered in South Dakota by the famous paleontologist Edward Drinker Cope, and was known for decades by the now-discarded name Trachodon.
The largest prehistoric turtle that ever lived, the "type fossil" of Archelon was discovered in South Dakota in 1895 (an even bigger specimen, measuring over a dozen feet long, was unearthed in the 1970's). Today, the closest living relative of Archelon is the soft-shelled sea turtle known as the Leatherback. More about Archelon
A close relative of the better-known Diplodocus, Barosaurus was virtually indistinguishable from its harder-to-pronounce cousin, save for it longer neck. Like other sauropods, Barosaurus wasn't the brainiest dinosaur that ever lived, and it probably spent its entire life foraging the tops of trees, safe from predators thanks to its sheer bulk.
Dinosaurs weren't the only giant animals ever to live in South Dakota. Tens of millions of years after the dinosaurs went extinct, megafauna mammals like Brontotherium roamed the western plains in large, lumbering herds. This "thunder beast" did have one trait in common with its reptilian predecessors, though: its unusually small brain. More about Brontotherium
One of the first ornithopod dinosaurs to be identified in the United States, Camptosaurus has a complicated taxonomic history. The first specimen was discovered in Wyoming, and a separate species a few decades later in South Dakota. Recently, paleontologists concluded that this South Dakota species deserves its own genus, and renamed it Osmakasaurus.
One of the more controversial dinosaurs on the official rolls, not only is Dracorex named after the Harry Potter books (its full name is Dracorex hogwartsia), but this pachycephalosaur may not even deserve its own genus. A recent analysis has concluded that Dracorex was really a growth stage of a better-known genus of thick-headed dinosaur, Pachycephalosaurus. More about Dracorex
One of the longest-lasting predatory mammals in the fossil record, various species of Hyaenodon persisted in North America for a whopping 20 million years, from 40 million to 20 million years ago. Numerous individuals of this wolf-like carnivore have been unearthed in South Dakota, where Hyaenodon preyed on plant-eating megafauna mammals. More about Hyaenodon
The second-most-famous dinosaur of all time--after T. Rex, below--numerous fossils of Triceratops have been discovered in South Dakota and surrounding states. This ceratopsian possessed one of the biggest, most ornate heads of any living creature; even today, fossilized Triceratops skulls command big bucks at natural-history auctions. More about Triceratops
9. Tyrannosaurus Rex
South Dakota was home to the most famous Tyrannosaurus Rex specimen of all time: Tyrannosaurus Sue, which was discovered by amateur fossil hunter Sue Hendrickson in 1990. After legal disputes about Sue's provenance, the reconstructed skeleton was auctioned off to the Field Museum of Natural History (in far-off Chicago) for $8 million. More about Tyrannosaurus Rex