Pronunciation: TOHK-i-SOR-us
Meaning: Ostrich (foot) lizard
Author/s: Kurzanov and Osmólska (1991)
Synonyms: None known
First Discovery: Gobi, Mongolia
Discovery Chart Position: #362
Tochisaurus nemegtensis
Upon description in 1991, the remains of Tochisaurus included the only complete troodontid metatarsus — the foot bones between the toes (phalanges) and the tarsus (the cluster of bones that joins the metatarsus to the ankle) — known from Asia. Unfortunately, the only complete troodontid metatarsus known from Asia is the only remains that are known of Tochisaurus, though it is rather unique.
The bones are slender, and the second metatarsal is unusually short, which suggests the typical troodontid "killing claw" that would have been attached to it was fairly modest. With fossil troodontids generally lacking in comparable parts, working out which one Tochisaurus is most closely related to has drawn a blank, but hey, what's wrong with a wild stab in the dark now and again?
In 1987, Osmólska suspected that Tochisaurus may be the same critter as Borogovia because they were discovered in the same Mongolian rock formation and both have distinctive second toes, although those of Borogovia were the same length as its other toes and sport an unusually flat claw (ungual). There were whispers from certain quarters in the not-too-distant past of Tochisaurus perhaps being the Asian version of "Stenonychosaurus inequalis", which is, funnily enough, owner of the only complete troodontid metatarsus known from North America. But Phil Currie put the kibosh on that particular theory when he sunk the latter into Troodon formosus, along with "Polyodontosaurus grandis" and "Pectinodon bakkeri", in 1987.
The bones are slender, and the second metatarsal is unusually short, which suggests the typical troodontid "killing claw" that would have been attached to it was fairly modest. With fossil troodontids generally lacking in comparable parts, working out which one Tochisaurus is most closely related to has drawn a blank, but hey, what's wrong with a wild stab in the dark now and again?
In 1987, Osmólska suspected that Tochisaurus may be the same critter as Borogovia because they were discovered in the same Mongolian rock formation and both have distinctive second toes, although those of Borogovia were the same length as its other toes and sport an unusually flat claw (ungual). There were whispers from certain quarters in the not-too-distant past of Tochisaurus perhaps being the Asian version of "Stenonychosaurus inequalis", which is, funnily enough, owner of the only complete troodontid metatarsus known from North America. But Phil Currie put the kibosh on that particular theory when he sunk the latter into Troodon formosus, along with "Polyodontosaurus grandis" and "Pectinodon bakkeri", in 1987.
Etymology
Tochisaurus is derived from the Mongolian "tokh" (ostrich) and the Greek "sauros" (lizard), named for the "general similarity of its metatarsus to that of an ostrich".The species epithet, nemegtensis, means "from Nemegt" in Latin.
Discovery
The remains of Tochisaurus were discovered by paleontological expeditions
of the USSR Academy of Sciences (RAS) in the Nemegt Formation,
Nemegt Basin, southern Gobi desert, Mongolia, in 1948. The holotype (listed as PIN 551-224) is an almost complete metatarsus: the longest set of bones between the ankle and toes.
