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{{Taxobox
{{Taxobox
| name = ''Trierarchuncus''
| name = ''Trierarchuncus''
| fossil_range = [[Late Cretaceous]], {{fossilrange|66.002|66}}
| fossil_range = [[Late Cretaceous]], {{fossilrange|66.2|66}}
| regnum = [[Animal]]ia
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| phylum = [[Chordate|Chordata]]

Revision as of 14:56, 10 July 2020

Trierarchuncus
Temporal range: Late Cretaceous, 66.2–66 Ma
Scientific classification
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Trierarchuncus

Fowler et al., 2020
Binomial name
Trierarchuncus prairiensis
Fowler et al., 2020

Trierarchuncus is a monotypic genus of alvarezsaurid theropod which includes a single species, Trierarchuncus prairiensis, which is known from fossils found in deposits of the Hell Creek Formation in Montana.[1][2] It is the youngest known alvarezsaurid and one of the last non-avian dinosaurs, going extinct during the Cretaceous–Paleogene extinction event, which occurred approximately 66 million years ago.[3][1]

Discovery and naming

The holotype was discovered in Montana in 1988 and it was informally known as the "Hell Creek alvarezsaur".[4] The then unnamed species was not mentioned again until it was mentioned briefly in the 2018 Society of Vertebrate Paleontology abstract book. The species and genus were scientifically described by Denver Fowler and colleagues in 2020 based on three claw phalanges from MD-I-2, including the holotype MOR 6622, the distal end of a radius and fragmentary metatarsal.

The first part of the generic name, Trierarch, means "triarch" (the title of captain of the trireme in classical Greece); the second, uncus, is translated from Latin as "hook". The species name means "from the prairie" and refers to the plains of eastern Montana where the remains were discovered.[1]

Description

Trierarchuncus was described by Fowler based upon several differences, especially on the three phalanges, the radius and the metatarsals. Trierarchuncus is known from its arms, feet and toes. Like its relatives, Trierarchuncus would have been feathered, with short arms bearing one clawed digit, a bird-like head and long legs.[1]

Trierarchuncus is estimated to be around 30 centimetres (12 in) tall and 80-100 centimeters (31-39 inches) in length when fully grown.[1]

Biogeography

Trirerarchuncus represents one of the few known alvarezsaurids from North America.[4][2] At 66 million years old, it is the youngest known alvarezsaurid and is one of the youngest non-avian dinosaurs in general, like its contemporaries Tyrannosaurus rex and Triceratops. Additionally, another Hell Creek alvarezsaurid, called "Ornithomimus" minutus, is known, but Fowler et al., did not refer it to Trirerarchuncus.[1]

Classification

Cladogram according to Fowler et al., 2020:[1]

References

  1. ^ a b c d e f g Denver W. Fowler; John P. Wilson; Elizabeth A. Freedman Fowler; Christopher R. Noto; Daniel Anduza; John R. Horner (2020). "Trierarchuncus prairiensis gen. et sp. nov., the last alvarezsaurid: Hell Creek Formation (uppermost Maastrichtian), Montana". Cretaceous Research. in press: Article 104560. doi:10.1016/j.cretres.2020.104560.
  2. ^ a b "Dinosaur distribution (Late Cretaceous; North America; Montana)." Weishampel, et al. (2004). Page 584.
  3. ^ Fortey, Richard (1999). Life: A natural history of the first four billion years of life on Earth. Vintage. pp. 238–260. ISBN 978-0-375-70261-7.
  4. ^ a b Hutchinson and Chiappe, 1998. The first known alvarezsaurid (Theropoda: Aves) from North America. Journal of Vertebrate Paleontology. 18(3), 447–450.