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The Dinosaurs and Prehistoric Animals of Oklahoma

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The state of Oklahoma is as well-known for its dinosaurs as for its prehistoric amphibians and reptiles, as listed below. (See an interactive map of dinosaurs and prehistoric animals in the United States.)

1. Acrocanthosaurus

acrocanthosaurus
One of the largest carnivorous dinosaurs of the early Cretaceous period (about 125 million years ago), the "type fossil" of Acrocanthosaurus was discovered in Oklahoma shortly after the Second World War. This theropod's name, Greek for "high-spined lizard," refers to the distinctive neural spines on its back, which may have supported a Spinosaurus-like sail. More about Acrocanthosaurus

2. Cacops

cacops
Dmitri Bogdanov
One of the most reptile-like amphibians of the early Permian period, Cacops was a squat, cat-sized creature with stubby legs, a short tail, and a lightly armored back. There's some evidence that Cacops was also equipped with relatively advanced eardrums, a necessary adaptation for life on the dry Oklahoma plains. More about prehistoric amphibians

3. Cotylorhynchus

cotylorhynchus
Dmitri Bogdanov
A close relative of Dimetrodon, below, Cotylorhynchus adhered to the classic pelycosaur body plan: a huge, bloated trunk (which held all of the intestines this prehistoric reptile needed to digest tough vegetable matter), a tiny head, and stubby, splayed legs. Three species of Cotylorhynchus have been discovered in Oklahoma and its southern neighbor, Texas.

4. Dimetrodon

dimetrodon
Charles R. Knight
Often mistaken for a dinosaur, Dimetrodon was actually a type of prehistoric reptile known as a pelycosaur, and lived well before the classic age of dinosaurs (during the Permian period). No one knows the exact function of Dimetrodon's distinctive sail; it was probably a sexually selected characteristic, and may have helped this reptile absorb (and dissipate) heat. More about Dimetrodon

5. Diplocaulus

diplocaulus
Nobu Tamura
The remains of the bizarre, boomerang-headed Diplocaulus have been found all over the state of Oklahoma, which was much swampier 280 million years ago than it is today. Diplocaulus' V-shaped noggin may have helped this prehistoric amphibian to navigate strong river currents, and may also have deterred larger predators from swallowing it whole!

6. Saurophaganax

saurophaganax
Sergey Krasovskiy
The official state dinosaur of Oklahoma, Saurophaganax was a close relative of the better-known Allosaurus--and, in fact, it may have been a species of Allosaurus, which would consign the name Saurophaganax to the trash heap of paleontology. In fact, the Saurophaganax skeleton on display at the Oklahoma Museum of Natural History includes some Allosaurus bones!

7. Sauroposeidon

sauroposeidon
H. Kyoht Luterman
Like many sauropod dinosaurs, Sauroposeidon was "diagnosed" based on a handful of vertebrae found on the Oklahoma side of the Texas-Oklahoma border. The difference is, these vertebrae were huge, putting Sauroposeidon in the 100-ton weight class (and thus making it one of the biggest sauropods that ever lived, possibly rivaling the South American Argentinosaurus). More about Sauroposeidon

8. Varanops

varanops
Dmitri Bogdanov
Yet another pelycosaur--and thus closely related to Dimetrodon and Cotylorhynchus (above)--Varanops was important for being one of the last of its kind on the earth, dating all the way to the late Permian period (about 260 million years ago). By the start of the Triassic period, all the pelycosaurs had gone extinct, muscled out of the scene by archosaurs and therapsids.
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