Tochisaurus
From Mongolian 'tochi' meaning 'ostrich' and Greek 'sauros' meaning 'lizard', alluding to its ostrich-like form.
Late Cretaceous stages
Tochisaurus is a genus of small troodontid theropod dinosaur from the Late Cretaceous Period of Mongolia. The type (and only named) species is Tochisaurus nemegtensis.
Under dispute
Tochisaurus nemegtensis is known only from a single metatarsus. It is accepted as a valid troodontid on the distinctive slender, functionally didactyl foot (Kurzanov and Osmólska, 1991), but the single-element holotype prevents any finer placement. It is placed at Troodontidae incertae sedis.
Diagnosis
- Metatarsus very slender, distinctly more so than in other troodontids including Troodon formosus.
- Metatarsal II strongly reduced, with distal articular head much smaller than those of metatarsals III and IV, implying reduction of the second pedal digit.
- Proximal articular surface of metatarsus inclined relatively strongly anterodistally, a feature absent in the contemporaneous Saurornithoides junior.
- Metatarsal II proximally about half the width of metatarsal IV, proportionally narrower than in Saurornithoides junior.
Species
Tochisaurus nemegtensis Kurzanov & Osmólska, 1991
Type species
Named for the Nemegt Formation of Mongolia, where the holotype was discovered.
- Holotype
- PIN 551-224 , Paleontological Institute, Russian Academy of Sciences
- Material
- Almost complete metatarsus.
- Horizon
- Nemegt Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
- Locality
- Nemegt, Ömnögovi, Mongolia
References
- Kurzanov, S. M.; Osmólska, H. (1991). Tochisaurus nemegtensis gen. et sp. n., a new troodontid dinosaur (Dinosauria, Theropoda) from Mongolia. Acta Palaeontologica Polonica 36(1): 69-76. kurzanov1991a
-
Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.
Source of the body length estimate.
jones2026c