''Haplocheirus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

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 ...

. Upon its description, it was considered the oldest alvarezsauroid, predating all other members by about 63 million years. This has subsequently been questioned. A 2019 study considered ''Haplocheirus'' a

compsognathid Compsognathidae is a family of coelurosaurian theropod dinosaurs. Compsognathids were small carnivores, generally conservative in form, hailing from the Jurassic and Cretaceous Periods. The bird-like features of these species, along with other d ...

instead of an alvarezsauroid, while a 2022 study considered it to have more similarities with

ornithomimosaurs Ornithomimosauria ("bird-mimic lizards") are theropod dinosaurs which bore a superficial resemblance to the modern-day ostrich. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia (now Asia, Europe and Nor ...

. ''Haplocheirus'' was described in 2010 from a fossil specimen found from the 160-million-year-old

Shishugou Formation The Shishugou Formation () is a geological formation in Xinjiang, China. Its strata date back to the Late Jurassic period. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, David B; et al. (2004). "Din ...

in the

Junggar Basin The Junggar Basin () is one of the largest sedimentary basins in Northwest China. It is located in Xinjiang, and enclosed by the Tarbagatai Mountains of Kazakhstan in the northwest, the Altai Mountains of Mongolia in the northeast, and the Heave ...

of northwestern

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...

. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specim ...

is ''H. sollers'', meaning "simple-handed skillful one", referencing its hypothesized behavior of using its three-fingered hands for activities that other alvarezsauroids could not perform, such as catching prey.

Description

''Haplocheirus'' had an enlarged thumb claw like alvarezsaurids, but also retained two other functional fingers, unlike alvarezsaurids, where only the thumb was significantly large and clawed. It had long legs and was probably a fast runner. It had large pupils for proportional for an animal its size. As an alvarezsaur, it was among the largest members of the clade, with an estimated adult body mass of , though it was surpassed by ''

Bonapartenykus ''Bonapartenykus'' (meaning " José F. Bonaparte's claw") is a monospecific genus of alvarezsauroid dinosaur from Argentina that lived during the Late Cretaceous (Campanian-Maastrichtian) in what is now the upper Allen Formation of the Río Neg ...

''. The total length of the holotype, which was a still-growing juvenile, would have been roughly , depending on the length of the tail. According to one study, it and the alvarezsaurid '' Shuvuuia'' were likely

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

animals.

Footnotes

References

External links

*Richard Ston
Bird-Dinosaur Link Firmed Up, And in Brilliant Technicolor
''Science'' 29 January 2010: Vol. 327. no. 5965, p. 508, DOI 10.1126/science.327.5965.508 *Doreen Walto
New dinosaur discovery solves evolutionary bird puzzle
''BBC News'' Thursday, 28 January 2010 Alvarezsaurs Monotypic dinosaur genera Oxfordian life Late Jurassic dinosaurs of Asia Jurassic China Fossils of China Paleontology in Xinjiang Fossil taxa described in 2010 {{theropod-stub

Description

See also

Footnotes

References

External links