Colorado's fossil record has two peaks: Jurassic dinosaurs, led by Allosaurus (39 records) and Stegosaurus (24), and an Eocene lake bed full of insects and plants. The state fossil is Stegosaurus, adopted in 1982.
The Jurassic rock is the Morrison Formation. Garden Park, near Cañon City, gave Yale the first nearly complete skeletons of Stegosaurus, Ceratosaurus and Allosaurus in the 1880s. Today 493 dinosaur records come from Colorado, with Triceratops and Tyrannosaurus in the younger Cretaceous rock.
The largest group in the state's 9,344 fossil records is the Paleogene, with 5,697. Most come from places like Florissant, where about 34 million years ago volcanic ash from nearby eruptions settled into a lake and preserved leaves, fish and more than 1,500 species of insects. Eruptions of that kind shaped much of the state, as volcanoes in Colorado explains.
Between the two, Colorado was seabed, 80 million years ago. The sea left Baculites (30 records) and the crushing-toothed shark Ptychodus (10).
Dinosaurs found in Colorado
The Paleobiology Database lists 493 dinosaur finds in Colorado. These are the best documented.
- Allosaurus: A large Late Jurassic predator, 8 to 9 m long, with three-fingered hands and serrated teeth. Found 39 times, from 158 to 143 million years ago.
- Stegosaurus: A plant eater with two rows of upright back plates and four spikes on its tail. Late Jurassic. Found 24 times, from 155 to 143 million years ago.
- Apatosaurus: A Late Jurassic long-necked plant eater about 21 m long. Many scientists now treat Brontosaurus as a separate genus. Found 17 times, from 155 to 143 million years ago.
- Diplodocus: A Late Jurassic long-necked plant eater about 25 m long, with a whip-like tail and peg-shaped teeth. Found 14 times, from 155 to 143 million years ago.
- Brachiosaurus: A Late Jurassic plant eater with front legs longer than its hind legs, so its back sloped and its neck rose high. Found 8 times, from 155 to 143 million years ago.
- Tyrannosaurus (T. rex): A meat eater up to 12 m long with a bite strong enough to crush bone. Lived in the Late Cretaceous. Found 7 times, from 72.2 to 66 million years ago.
- Triceratops: A plant eater with three horns and a bony neck frill. It lived until the extinction 66 million years ago. Found 5 times, from 72.2 to 66 million years ago.
- Camarasaurus: A long-necked plant eater with a short, blunt skull and spoon-shaped teeth. Common in Late Jurassic rock. Found 38 times, from 155 to 143 million years ago.
- Ceratosaurus: A Late Jurassic predator about 6 m long with a horn on its snout and small bony studs down its back. Found 6 times, from 155 to 143 million years ago.
- Albertosaurus: A Late Cretaceous tyrannosaur about 9 m long, smaller and lighter than T. rex. Found 2 times, from 83.6 to 66 million years ago.
- Edmontosaurus: A duck-billed dinosaur up to about 12 m long, with hundreds of small teeth packed into its cheeks for grinding plants. Found 2 times, from 72.2 to 66 million years ago.
- Grallator: Small three-toed footprints of a meat-eating dinosaur, common in Triassic and Jurassic rock. A track name. Found 14 times, from 227 to 72.2 million years ago.
Other fossils found in Colorado
Beyond dinosaurs, the Colorado record includes these animals and plants.
- Equus (horse): The horse genus, with zebras and donkeys. Horses evolved in North America and died out there in the Ice Age. Found 11 times, from 4.7 to 0.01 million years ago.
- Mosasaurus: A giant sea lizard up to about 12 m long, a relative of snakes and monitor lizards. It died out 66 million years ago. Found 2 times, from 83.6 to 72.2 million years ago.
- Mammut (mastodon): A browsing Ice Age elephant relative with long, upward-curving tusks and ridged, low-crowned teeth. Not a mammoth. Found 1 time, from 23 to 5.3 million years ago.
- Calamites (giant horsetail): A tree-sized relative of horsetails, up to about 20 m tall. Common in Carboniferous coal swamps. Found 6 times, from 359 to 252 million years ago.
- Baculites (baculite): An ammonite with a straight, rod-shaped shell instead of a coil, common in Late Cretaceous seas. Found 30 times, from 93.9 to 66 million years ago.
- Ptychodus: A Late Cretaceous shark with broad, ridged teeth suited to crushing clams and other hard-shelled prey. Found 10 times, from 101 to 89.8 million years ago.
- Mammuthus (mammoth): An Ice Age elephant relative with long curved tusks. Woolly mammoths lived in the north, Columbian ones farther south. Found 1 time, from 0.13 to 0.01 million years ago.
- Tylosaurus: A Late Cretaceous mosasaur about 12 m long, with a toothless bony tip on its snout. Found 1 time, from 85.7 to 83.6 million years ago.
- Bison: The bison genus. Ice Age bison were larger than today's, and Bison latifrons had horns spanning about 2 m. Found 3 times, from 0.13 to 0.01 million years ago.
- Canis (wolf, coyote or dog): The genus of wolves, coyotes and dogs. Ice Age fossils include gray wolves. The dire wolf now has its own genus. Found 11 times, from 1.4 to 0.01 million years ago.
- Megacerops (titanothere): A huge, rhino-like relative of horses from the Late Eocene, with a forked horn on its nose. Found 8 times, from 37 to 33.9 million years ago.
- Squalicorax (crow shark): A Late Cretaceous shark with serrated, triangular teeth. Its name means crow shark. Found 10 times, from 101 to 72.2 million years ago.
State symbols
- State fossil: Stegosaurus (adopted 1982) Read the statute
Designated by executive order of Gov. Richard Lamm 28 Apr 1982 (Governor's Executive Order D 002 82 per secondary sources; archives.colorado.gov and leg.colorado.gov pages return 403 to scripted fetch, so the order itself was not read). Not found in C.R.S. 24-80-9xx. Colorado Geological Survey (state agency) page names Stegosaurus stenops as state fossil. Legislature SB23-145 (approved 22 May 2023) created a 'stegosaurus state fossil license plate' https://leg.colorado.gov/bills/SB23-145. Stegosaurus is the state fossil and no separate state dinosaur exists.
How the land changed
Every fossil records the place it was buried in. Reading those places period by period shows how Colorado changed.
- Carboniferous (359 to 299 Ma): most fossils from this time come from a shallow sea.
- Jurassic (201 to 143 Ma): most fossils from this time come from rivers and lakes.
- Cretaceous (143 to 66 Ma): most fossils from this time come from a shallow sea.
- Paleogene (66 to 23 Ma): most fossils from this time come from rivers and lakes.
- Neogene (23 to 2.6 Ma): most fossils from this time come from dry land.
- Quaternary (2.6 to 0 Ma): most fossils from this time come from rivers and lakes.
Oldest and youngest finds in Colorado
The oldest find in the Colorado record is Strepsodiscus, dated to about 497 million years ago. The youngest is Microtus, from the last 12,000 years.
Fossil finds in Colorado by period
| Period | Million years ago | Finds | Most common group |
|---|---|---|---|
| Cambrian | 539 to 487 | 6 | Invertebrates |
| Ordovician | 487 to 443 | 145 | Invertebrates |
| Devonian | 420 to 359 | 230 | Invertebrates |
| Carboniferous | 359 to 299 | 351 | Invertebrates |
| Permian | 299 to 252 | 78 | Invertebrates |
| Triassic | 252 to 201 | 104 | Reptiles, amphibians and birds |
| Jurassic | 201 to 143 | 609 | Dinosaurs |
| Cretaceous | 143 to 66 | 1,296 | Invertebrates |
| Paleogene | 66 to 23 | 5,697 | Invertebrates |
| Neogene | 23 to 2.6 | 231 | Mammals |
| Quaternary | 2.6 to 0 | 597 | Mammals |
Frequently asked questions
What is the state fossil of Colorado?
Colorado has designated Stegosaurus as its state fossil, adopted in 1982.
What dinosaurs have been found in Colorado?
The best-documented dinosaurs in the Colorado record are Allosaurus, Stegosaurus, Apatosaurus, Diplodocus and Brachiosaurus. The Paleobiology Database lists 493 dinosaur finds there.
How many fossils have been found in Colorado?
The Paleobiology Database records 9,344 fossil finds in Colorado, covering 2,419 kinds of animals, plants and other life.
What is the oldest fossil found in Colorado?
The oldest find in the Colorado record is Strepsodiscus, dated to about 497 million years ago.
How can I see fossils near me in Colorado?
Type a town or ZIP code into the search box at the top of this page, or use your location, to see the fossils recorded within 25 to 200 km. Natural history museums and state fossil parks are the best places to see real specimens.
Keep exploring
More fossil states: California, Texas, Wyoming, Florida, Utah, New Mexico, all 50 states.
Credits and data
- Fossil finds: the Paleobiology Database, licensed CC BY 4.0. Counts are records in the database, which reflect research effort as well as geology.
- Ancient Earth maps and plate motion: PALEOMAP PaleoDEMs, Scotese and Wright (2018), CC BY 4.0, doi:10.5281/zenodo.5460860.
- Place names: US Census Gazetteer (public domain) and GeoNames, CC BY 4.0.
- Silhouettes: PhyloPic contributors (Marie Aimee ALLARD, Olivia Binfield, Jagged Fang Designs, David Orr, Amy Beauvois, Steven Traver, Guillaume Dera, Margot Michaud, An Ignorant Atheist, U.S. National Park Service (vectorized by William Gearty), Scott Hartman).