Flat Creek Inn

Dinosaurs of Wyoming

Photo copyright 2005 by David Monniaux

Wyoming, with its expansive plains and rugged landscapes, is not only known for its stunning natural beauty and rich cowboy history but also for being a treasure trove of dinosaur fossils. This state has unearthed some of the most iconic and significant dinosaur discoveries in the world—no prehistoric B-listers here. Let’s take a journey back in time to explore the fascinating dinosaurs of Wyoming. 

Tyrannosaurus rex

One of the most famous dinosaurs in the world, Tyrannosaurus rex called Wyoming home (though to be honest, it probably didn’t know the place was called “Wyoming”). T. rex fossils have been found in the Hell Creek Formation, a geologic formation that spans parts of Wyoming, Montana, and the Dakotas. Known for its massive size, powerful jaws, sharp teeth, and for nearly outrunning that jeep in Jurassic Park, T. rex was the apex predator of its time, dominating the late Cretaceous period around 68 to 66 million years ago​.

Side note: have you ever wondered why Tyrannosaurus rex gets a cool last name while the rest of the dinosaurs do? Turns out that's just the genus and species name. Other dinosaurs have them too (like Triceratops horridus) but they're usually not nearly as fun to say.


Triceratops is another iconic dinosaur whose fossils have been discovered in Wyoming’s Hell Creek Formation. This herbivorous dinosaur, known for its three distinctive horns and large frill, lived during the same period as T. rex. They probably knew each other and—we can’t stress this enough—did not get along. Triceratops used its horns for defense against predators like T. rex … and possibly in combat with other Triceratops for territory or mates​​. You think elk mating gets rough? You obviously haven’t seen a bunch of testosteroned-up Triceratops competing for the ladies.


Apatosaurus, often confused with Brontosaurus, is one of the giant sauropods that lived during the late Jurassic period around 150 million years ago. Known for its long neck and tail, Apatosaurus was a massive herbivore that could reach lengths of up to 75 feet​. Fossils of Apatosaurus have been found in the Morrison Formation, a sedimentary rock formation that extends across several western states, including Wyoming. 


Stegosaurus, another resident of the Morrison Formation, is easily recognized by the double row of large, bony plates along its back and the spikes on its tail. This dinosaur lived during the late Jurassic period and was a herbivore. The plates may have been used for temperature regulation, protection from predators, or just for looking fire (as the kids say). 


Diplodocus, another long-necked sauropod (or “longneck” to those whose dinosaur knowledge is based on The Land Before Time), shared its habitat with Apatosaurus and lived during the late Jurassic period. Known for its incredibly long neck and tail, Diplodocus could reach lengths of up to 90 feet, making it one of the longest dinosaurs ever to live. Its fossils have also been unearthed in the Morrison Formation, showcasing the diversity of sauropod species that lived in this area​.


Allosaurus was a dominant predator of the late Jurassic period and also roamed the region that is now Wyoming. Sometimes he gets a bad rap for being almost as big as T. rex but not quite, a fact that probably bugged him to no end, even though T. rex wouldn’t come along for millions of years. Allosaurus fossils have been found in—you guessed it—the Morrison Formation, which is apparently where all the cool dinosaurs hung out​.


Deinonychus, meaning "terrible claw," was a small but formidable theropod dinosaur that lived during the early Cretaceous period, approximately 115 to 108 million years ago. Discovered in the Cloverly Formation, Deinonychus measured about 10 feet in length and featured a distinctive large, sickle-shaped claw on each hind foot. This agile predator likely hunted in packs, using its speed and intelligence to take down larger prey. If this description immediately brought to mind Velociraptor, you’re not far off. The raptors from Jurassic Park were scaled up to be scarier, making them about the actual size of their relative, Deinonychus. 

This post is brought to you by Flat Creek Inn


Ryan Kunz is a copywriter and freelance writer who writes on a variety of topics, including media, the outdoors, and whatever else strikes his fancy. He didn't think he'd get to write about dinosaurs of Wyoming tonight, but life, uh, finds a way.

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