South Dakota's fossils fall into two groups: Cretaceous dinosaurs and sea reptiles in the west and center, and Oligocene mammals in the Badlands. Triceratops is the state fossil, adopted in 1988, and the state's 4,583 fossil records include 159 dinosaur finds.
The best-known single find is Sue, one of the most complete Tyrannosaurus skeletons known. Sue was found in August 1990 on the Cheyenne River Indian Reservation near Faith, in Hell Creek rock, and the Field Museum bought it in 1997. The database has 11 Tyrannosaurus records and 20 of Triceratops from the same river-and-delta landscape.
Earlier in the Cretaceous, 90 million years ago, a shallow sea lay over South Dakota. Its chalk and shale hold Ptychodus (49 records), Squalicorax (31), Pteranodon (13), Mosasaurus (5) and the giant sea turtle Archelon (3).
The Paleogene has 1,659 records and the Neogene 753, including the mammals of the White River Badlands: oreodonts, titanotheres and early camels. Camelops, one of the last camels, is the youngest find.
At Hot Springs, a Pleistocene sinkhole trapped more than 60 mammoths, most of them Columbian mammoths.
Dinosaurs found in South Dakota
The Paleobiology Database lists 159 dinosaur finds in South Dakota. These are the best documented.
- Triceratops: A plant eater with three horns and a bony neck frill. It lived until the extinction 66 million years ago. Found 20 times, from 72.2 to 66 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 11 times, from 72.2 to 66 million years ago.
- Allosaurus: A large Late Jurassic predator, 8 to 9 m long, with three-fingered hands and serrated teeth. Found 3 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 2 times, from 149 to 143 million years ago.
- Ankylosaurus: A Late Cretaceous plant eater covered in bony armor, with a heavy bone club at the end of its tail. Found 1 time, from 72.2 to 66 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 1 time, from 155 to 143 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 8 times, from 72.2 to 66 million years ago.
- Pachycephalosaurus: A Late Cretaceous plant eater with a dome of thick bone on its skull. It lived near the end of the dinosaur age. 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 4 times, from 155 to 143 million years ago.
- Troodon: A small Late Cretaceous dinosaur first named from a single tooth. Close relatives had large eyes and big brains. Found 3 times, from 72.2 to 66 million years ago.
- Torosaurus: A Late Cretaceous horned dinosaur with a skull up to about 2.5 m long, one of the longest of any land animal. Found 2 times, from 72.2 to 66 million years ago.
- Ornithomimus (ostrich mimic): A toothless, ostrich-like runner about 3.5 m long. Some specimens preserve feather impressions. Found 3 times, from 72.2 to 66 million years ago.
Other fossils found in South Dakota
Beyond dinosaurs, the South Dakota record includes these animals and plants.
- Pteranodon: A toothless flying reptile with a wingspan up to about 6 m and a tall crest. It was not a dinosaur. Found 13 times, from 83.6 to 72.2 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 5 times, from 83.6 to 66 million years ago.
- Equus (horse): The horse genus, with zebras and donkeys. Horses evolved in North America and died out there in the Ice Age. Found 6 times, from 4.7 to 0.21 million years ago.
- Ptychodus: A Late Cretaceous shark with broad, ridged teeth suited to crushing clams and other hard-shelled prey. Found 49 times, from 101 to 85.7 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 2 times, from 1.4 to 0.01 million years ago.
- Baculites (baculite): An ammonite with a straight, rod-shaped shell instead of a coil, common in Late Cretaceous seas. Found 25 times, from 93.9 to 66 million years ago.
- Squalicorax (crow shark): A Late Cretaceous shark with serrated, triangular teeth. Its name means crow shark. Found 31 times, from 101 to 72.2 million years ago.
- Archelon: The largest sea turtle known, up to about 4.6 m long, with a leathery shell instead of a hard one. Late Cretaceous. Found 3 times, from 83.6 to 66 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 12.5 to 9.4 million years ago.
- Merycoidodon (oreodont): An Oligocene oreodont about 1.4 m long, an extinct plant eater related to camels, not to sheep or pigs. Found 75 times, from 37 to 18.5 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 2 times, from 0.77 to 0.13 million years ago.
- Megacerops (titanothere): A huge, rhino-like relative of horses from the Late Eocene, with a forked horn on its nose. Found 15 times, from 37 to 33.9 million years ago.
State symbols
- State fossil: Triceratops (adopted 1988) Read the statute
SDCL 1-6-16.1: 'Triceratops is hereby designated as the official fossil of the State of South Dakota.' Source: SL 1988 ch 6. Statute names a dinosaur as the state fossil; no separate state dinosaur designation found. PBDB: valid.
How the land changed
Every fossil records the place it was buried in. Reading those places period by period shows how South Dakota changed.
- Cambrian (539 to 487 Ma): most fossils from this time come from a coast or delta.
- 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 dry land.
- 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 dry land.
Oldest and youngest finds in South Dakota
The oldest find in the South Dakota record is Dicellomus, dated to about 507 million years ago. The youngest is Camelops, from the last 12,000 years.
Fossil finds in South Dakota by period
| Period | Million years ago | Finds | Most common group |
|---|---|---|---|
| Cambrian | 539 to 487 | 649 | Invertebrates |
| Ordovician | 487 to 443 | 11 | Invertebrates |
| Carboniferous | 359 to 299 | 7 | Fish and sharks |
| Permian | 299 to 252 | 4 | Fish and sharks |
| Jurassic | 201 to 143 | 27 | Dinosaurs |
| Cretaceous | 143 to 66 | 1,371 | Invertebrates |
| Paleogene | 66 to 23 | 1,659 | Mammals |
| Neogene | 23 to 2.6 | 753 | Mammals |
| Quaternary | 2.6 to 0 | 102 | Mammals |
Frequently asked questions
What is the state fossil of South Dakota?
South Dakota has designated Triceratops as its state fossil, adopted in 1988.
What dinosaurs have been found in South Dakota?
The best-documented dinosaurs in the South Dakota record are Triceratops, Tyrannosaurus, Allosaurus, Apatosaurus and Ankylosaurus. The Paleobiology Database lists 159 dinosaur finds there.
How many fossils have been found in South Dakota?
The Paleobiology Database records 4,583 fossil finds in South Dakota, covering 847 kinds of animals, plants and other life.
What is the oldest fossil found in South Dakota?
The oldest find in the South Dakota record is Dicellomus, dated to about 507 million years ago.
How can I see fossils near me in South Dakota?
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 (Jagged Fang Designs, artrociraptor, Scott Hartman, Marie Aimee ALLARD, Amy Beauvois, David Orr, An Ignorant Atheist, U.S. National Park Service (vectorized by William Gearty), Margot Michaud, Danny Anduza).