Troodon
TRO-oh-don
"wounding tooth"
- Lived
- 84 to 66 million years ago, Late Cretaceous
- Diet
- Omnivore
- Length
- about 2.4 m (8 ft)
- Group
- Theropods, Troodontidae
- Found in
- Canada and United States
- Named by
- Leidy 1856
Size comparison
To scale
Scale in meters
Where its fossils were found
The evidence
Today
75 million years ago
Also reported from Russia and China.
Habitat
Fossils assigned to Troodon come from river plains in North America, including the Judith River Formation. Regional neighbors included Saurornitholestes, Edmontosaurus and Euoplocephalus.
Field notes
About Troodon
What it was like
Troodon was a small, bird-like theropod with large eyes, long legs, and a slender build suited for speed. It grew to about 2.4 meters (8 feet) long, including a long tail, and had teeth with fine serrations more like those of plant eaters than most meat-eating dinosaurs.
This unusual tooth shape suggests Troodon was probably an omnivore, eating both plants and small animals rather than hunting large prey. Its large eyes and relatively big brain for its size suggest it had sharp senses.
Its world
Troodon lived from about 84 to 66 million years ago, during the Late Cretaceous, mainly in what is now Alberta and Montana, with fossils also reported from Wyoming, Alaska, North Dakota, and Saskatchewan, and possible finds from Russia and China.
It shared its world with other small predators, including Saurornitholestes and Dromaeosaurus, as well as plant eaters such as Edmontosaurus and the armored Euoplocephalus and Edmontonia.
How it was found
Leidy named Troodon in 1856, making it one of the first dinosaurs described from North America, though it was originally mistaken for a lizard. Around 85 finds have since been linked to the genus, but scientists disagree about whether many of these fossils truly belong to Troodon or to closely related genera such as Stenonychosaurus and Latenivenatrix. Because the original fossils are so incomplete, the genus's validity is still actively debated among paleontologists.
Field gallery
More views of Troodon
Scenes reconstructed from the available fossil evidence.
Lived alongside
Found in the same rock formations
A rock formation can hold fossils laid down millions of years apart, so not every animal here met Troodon.
The evidence
The science behind Troodon
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- Troodon was named from a single tooth found in Montana.
- The tooth has serrations along its cutting edges.
Borrowed from relatives
- The slender body, large eyes and long legs usually shown for Troodon follow skeletons assigned to Stenonychosaurus.
- A feathered covering is inferred from close bird relatives such as Anchiornis.
Still unknown
- Which partial skeletons and teeth belong to the same species as the original tooth.
- Whether the proposed replacement specimen will settle the disagreement over its name.
- Its feather colors and the appearance of its young.
Often drawn wrong
- A bare, scaly body overlooks the feathered covering inferred for this bird-like dinosaur.
- Its hands should face inward, rather than hang with the palms facing the ground.
Discovery timeline
- 1856Named itLeidy
- 2009Close relativeHu et al.
- 2017Family treevan der Reest & Currie
- 2021How it fedFreimuth et al.
- 2025RedescriptionVarricchio, Hogan & Gardner
Key papers
The research behind what we know of Troodon
Named it
Named Troodon from a serrated tooth, initially identifying its owner as a lizard.
Notices of remains of extinct reptiles and fishes, discovered by Dr. F. V. Hayden in the bad lands of the Judith River, Nebraska Territory. Proceedings of the Academy of Natural Sciences of Philadelphia 8: 72-73
No link available
Close relative
Described richly feathered Anchiornis, a close bird relative that helps explain why Troodon is restored with feathers.
A pre-Archaeopteryx troodontid theropod from China with long feathers on the metatarsus. Nature 461: 640-643
Read the paper : A pre-Archaeopteryx troodontid theropod from China with long feathers on the metatarsus (opens in a new tab)Family tree
Separated skeletons formerly assigned to Troodon into Stenonychosaurus and Latenivenatrix, questioning whether the original tooth could identify a genus.
Troodontids (Theropoda) from the Dinosaur Park Formation, Alberta, with a description of a unique new taxon: implications for deinonychosaur diversity in North America. Canadian Journal of Earth Sciences 54: 919-935
Read the paper : Troodontids (Theropoda) from the Dinosaur Park Formation, Alberta, with a description of a unique new taxon: implications for deinonychosaur diversity in North America (opens in a new tab)How it fed
Described fossil pellets containing small mammal bones and proposed that a troodontid, possibly Troodon, had swallowed and regurgitated the prey.
Mammal‐bearing gastric pellets potentially attributable to Troodon formosus at the Cretaceous Egg Mountain locality, Two Medicine Formation, Montana, USA. Palaeontology 64: 699-725
Read the paper : Mammal‐bearing gastric pellets potentially attributable to Troodon formosus at the Cretaceous Egg Mountain locality, Two Medicine Formation, Montana, USA (opens in a new tab)Redescription
Described troodontid bones from embryos to adults and proposed a replacement name-bearing specimen to preserve Troodon as the name for this animal.
Troodontid specimens from the Cretaceous Two Medicine Formation of Montana (USA) and the validity of Troodon formosus. Journal of Paleontology 99: 219-240
Read the paper : Troodontid specimens from the Cretaceous Two Medicine Formation of Montana (USA) and the validity of Troodon formosus (opens in a new tab)
Close relatives
Other members of Troodontidae
Sources: Wikidata