Stenonychosaurus
sten-ON-i-koh-SORE-us
"narrow claw lizard"
- Lived
- 84 to 66 million years ago, Late Cretaceous
- Diet
- Omnivore
- Length
- about 2.5 m (8 ft)
- Group
- Theropods, Troodontidae
- Found in
- Canada and United States
- Named by
- Sternberg 1932
Size comparison
To scale
Scale in meters
Where its fossils were found
The evidence
Today
75 million years ago
Habitat
It probably lived on river plains in the Dinosaur Park Formation. Regional neighbors included Parasaurolophus, Styracosaurus and Corythosaurus.
Field notes
About Stenonychosaurus
What it was like
Stenonychosaurus was a small, lightly built theropod, an omnivore that ate both plants and animals. It had unusually large eyes for its size, hinting at good eyesight, and a proportionally large brain, one of the biggest among dinosaurs relative to body size. Its narrow, curved claws gave the genus its name. It grew to about 2.5 meters (8 feet) long, walked on two long legs built for speed, and had grasping hands well suited to catching small prey.
Its world
Stenonychosaurus lived in what is now Alberta, Canada, and parts of Montana and Wyoming in the United States, from about 84 to 66 million years ago, right up to the end of the Cretaceous. It shared its habitat with the swift Struthiomimus, the sickle-clawed Dromaeosaurus, and much larger predators such as Tyrannosaurus, as well as the horned Triceratops and the thick-skulled Pachycephalosaurus.
How it was found
Sternberg named Stenonychosaurus in 1932, and it has had a complicated history since, at times classified as the same animal as Troodon before later studies restored it as its own genus. Around 14 fossil finds are known today, spread across the Dinosaur Park, Oldman, and Lance formations.
Field gallery
More views of Stenonychosaurus
Scenes reconstructed from the available fossil evidence.
1 of 7
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 Stenonychosaurus.
The evidence
The science behind Stenonychosaurus
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- Partial skeletons show a lightly built animal with long legs and grasping forelimbs.
- Its skull had large eye sockets and room for a relatively large brain.
- The original finds included a foot, hand fragments and tail vertebrae.
Borrowed from relatives
- Feathers on the body and arms are inferred from feathered relatives such as Anchiornis.
- Missing skeletal parts are restored through comparisons with other troodontids, including Saurornithoides.
Still unknown
- The color and detailed pattern of its feathers.
- Whether it courted mates with displays or lived in groups.
- How its appearance changed as it grew.
Often drawn wrong
- Bare, scaly arms overlook the feathers expected in a troodontid.
- Its hands faced inward rather than palm down.
Discovery timeline
- 1932Named itSternberg
- 1969New findRussell
- 2017Family treevan der Reest & Currie
Key papers
The research behind what we know of Stenonychosaurus
Named it
Named the animal from a foot, hand fragments and tail bones found in Alberta.
Two New Theropod Dinosaurs from the Belly River Formation of Alberta. The Canadian field-naturalist 46: 99-105
Read the paper : Two New Theropod Dinosaurs from the Belly River Formation of Alberta (opens in a new tab)New find
Described a partial skeleton with large eyes, a relatively large brain and grasping forelimbs, and compared it with Saurornithoides.
A new specimen of Stenonychosaurus from the Oldman Formation (Cretaceous) of Alberta. Canadian Journal of Earth Sciences 6: 595-612
Read the paper : A new specimen of Stenonychosaurus from the Oldman Formation (Cretaceous) of Alberta (opens in a new tab)Family tree
Restored Stenonychosaurus as a separate genus and distinguished another troodontid, Latenivenatrix, from the same formation.
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)
Close relatives
Other members of Troodontidae
Sources: Wikidata