''Tochisaurus'' (meaning "Ostrich lizard") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of small

troodontid Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil discov ...

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

Period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...

. The type (and only named)

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

is ''Tochisaurus nemegtensis''. In 1948, a Soviet-Mongolian expedition found the remains of a small theropod in the

Gobi Desert The Gobi Desert (Chinese: 戈壁 (沙漠), Mongolian: Говь (ᠭᠣᠪᠢ)) () is a large desert or brushland region in East Asia, and is the sixth largest desert in the world. Geography The Gobi measures from southwest to northeast an ...

near Nemegt. In 1987 the find was reported by

Sergei Kurzanov Sergei Mikhailovich Kurzanov (Сергей Михайлович Курзанов, born 1947) is a Russian (formerly Soviet) paleontologist at the Paleontological Institute of the Russian Academy of Sciences. He is known mainly for his work in Mongo ...

and later that year discussed by

Halszka Osmólska Halszka Osmólska (September 15, 1930 – March 31, 2008) was a Polish paleontologist who had specialized in Mongolian dinosaurs. Biography She was born in 1930 in Poznań. In 1949, she began to study biology at Faculty of Biology and Earth Scie ...

who suggested it could represent a specimen of the troodontid ''

Borogovia ''Borogovia'' is a troodontid theropod dinosaur genus which lived during the Late Cretaceous Period, in what is now Mongolia. In 1971, a Polish-Mongolian expedition discovered the remains of a small theropod at the Altan Ula IV site, in the N ...

''. Later Osmólska understood it was a species new to science. It was formalized by Kurzanov and Osmólska in 1991 as ''Tochisaurus nemegtensis''. The generic name is derived from Mongolian ''toch, "

ostrich Ostriches are large flightless birds of the genus ''Struthio'' in the order Struthioniformes, part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There are ...

", in reference to the fact that the foot, like with that bird, is functionally didactyl, i.e. has only two weight-bearing toes. The specific name refers to the Nemegt.Kurzanov S.M., and Osmólska, H., 1991, "''Tochisaurus nemegtensis'' gen. et sp. n., a new troodontid (Dinosauria, Theropoda) from Mongolia", ''Acta Palaeontologia Polonica'' 36: 69-76 Its

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

, PIN 551-224, was found in a layer of the

Nemegt Formation The Nemegt Formation (also known as Nemegtskaya Svita) is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. The formation consists of river channel sediments and contains fossils of fish, turtles, crocodilian ...

, dating from the early

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

, about 69 million years old. It consists solely of the (left)

metatarsus The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the med ...

, the first discovered of an Asian troodontid. The first

metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the med ...

is missing. The top of the fossil shows some damage that was originally somewhat inexpertly restored. ''Tochisaurus'' is a bipedal dinosaur. The metatarsus has a length of 242 millimetres, showing it was a relatively large troodontid. The second metatarsal, 222 millimetres long, is very reduced and narrow. The joint surface on top of the metatarsus is sloped forward and downward. Based on the partial fossils, ''Tochisaurus'' is thought to have been a member of the

Troodontidae Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil disco ...

References

{{Taxonbar, from=Q1526317 Troodontids Late Cretaceous dinosaurs of Asia Nemegt fauna Fossil taxa described in 1991 Taxa named by Sergei Kurzanov Taxa named by Halszka Osmólska

See also

References