''Trierarchuncus'' (meaning "captain hook," after its single-clawed hands) is a monotypic genus of

alvarezsaurid Alvarezsauridae is a family of small, long-legged dinosaurs. Although originally thought to represent the earliest known flightless birds, they are now thought to be an early diverging branch of maniraptoran theropods. Alvarezsaurids were highly ...

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 ...

which includes a single species, ''Trierarchuncus prairiensis'', which is known from fossils found in deposits of the

Hell Creek Formation The Hell Creek Formation is an intensively studied division of mostly Upper Cretaceous and some lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana. The formation stretches over portions of ...

Montana Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...

. It is the youngest known alvarezsaurid and one of the last non-avian dinosaurs, going extinct during the

Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden extinction event, mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million y ...

, which occurred approximately 66 million years ago.

Discovery and naming

The first remains ware discovered in

in 1980 and it was informally known as the "Hell Creek alvarezsaur".Hutchinson and Chiappe, 1998. The first known alvarezsaurid (Theropoda: Aves) from North America. ''Journal of Vertebrate

Paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fos ...

''. 18(3), 447–450. The then unnamed species was not mentioned again until it was mentioned briefly in the 2018

Society of Vertebrate Paleontology The Society of Vertebrate Paleontology (SVP) is a professional organization that was founded in the United States in 1940 to advance the science of vertebrate paleontology around the world. Mission and Activities SVP has about 2,300 members inte ...

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 A trireme( ; derived from Latin: ''trirēmis'' "with three banks of oars"; cf. Greek ''triērēs'', literally "three-rower") was an ancient vessel and a type of galley that was used by the ancient maritime civilizations of the Mediterranean ...

classical Greece Classical Greece was a period of around 200 years (the 5th and 4th centuries BC) in Ancient Greece,The "Classical Age" is "the modern designation of the period from about 500 B.C. to the death of Alexander the Great in 323 B.C." (Thomas R. Martin ...

), while the second, ''uncus'', is translated from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

as "hook"; it can thus be translated as "captain hook", although its describers do not explicitly make the connection with the ''

Peter Pan Peter Pan is a fictional character created by Scottish novelist and playwright J. M. Barrie. A free-spirited and mischievous young boy who can fly and never grows up, Peter Pan spends his never-ending childhood having adventures on the mythi ...

character Character or Characters may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to The ...

. The specific name means "from the prairie" and refers to the plains of eastern Montana where the remains were discovered.

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. ''Trierarchuncus'' is estimated to be around tall and 140-150 centimeters (55-59 inches) in length when fully grown.

Classification

Cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

according to Fowler ''et al.'', 2020, with clade names added by definition:

Paleoecology

''Trierarchuncus'' represents one of the few known alvarezsaurids from North America."Dinosaur distribution (Late Cretaceous; North America; Montana)." Weishampel, et al. (2004). Page 584. 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 ''Tyrannosaurus'' is a genus of large theropod dinosaur. The species ''Tyrannosaurus rex'' (''rex'' meaning "king" in Latin), often called ''T. rex'' or colloquially ''T-Rex'', is one of the best represented theropods. ''Tyrannosaurus'' live ...

'' and ''

Triceratops ''Triceratops'' ( ; ) is a genus of herbivorous chasmosaurine ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous period, about 68 million years ago in what is now North America. It is ...

''. Additionally, another Hell Creek alvarezsaurid, called "''

Ornithomimus ''Ornithomimus'' (; "bird mimic") is a genus of ornithomimid dinosaurs from the Late Cretaceous Period of what is now North America. ''Ornithomimus'' was a swift bipedal theropod which fossil evidence indicates was covered in feathers, equippe ...

''" '' minutus'', is known, but Fowler ''et al.'' did not refer it to ''Trierarchuncus''.

References

Late Cretaceous dinosaurs of North America Hell Creek fauna Alvarezsaurids Fossil taxa described in 2020 {{Theropod-stub