Albertonykus
Encyclopedia
Albertonykus is a genus
of alvarezsaurid dinosaur
from lower Maastrichtian
-age (Upper Cretaceous) rocks of the Horseshoe Canyon Formation
of Alberta, Canada
. It is known from forelimb and hindlimb remains from multiple individuals. All but two of the specimens come from a bonebed dominated by Albertosaurus
. Albertonykus is interpreted as having fed on wood-nesting termite
s because the forelimbs appear to be specialized for digging, but are too short for burrowing. Albertonykus is the earliest-known North America
n alvarezsaurid; isolated remains of alvarezsaurids are known from later rock units in Montana
and Wyoming
(USA
).
The type species
is A. borealis, described by Nicholas Longrich and Philip Currie in a paper published in 2009 (which was available online as a preprint in 2008). The specific name (borealis) means "north".
and his crew found a site filled with the bones of the tyrannosaur Albertosaurus sarcophagus
. They unearthed the remains of at least nine different specimens of Albertosaurus in the single site, but stopped digging after just two weeks. The quarrying again produced the remains of over 20 specimens of Albertosaurus, and the quarry has yet to be fully excavated. It is not known why so many tyrannosaurs were found in one place: paleontologist Nick Longrich speculated that the site was part of a "predator trap", where food drew predators to their deaths. Close to a dozen arms and leg bones belonging to an unknown species of Albertosaurus were recovered in Alberta, Canada in 2002 by a team of scientist led by Philip J. Currie of the University of Alberta. The bones were then stored at the Royal Tyrrell Museum in Alberta.
In 2005 Nick Longrich, a paleontologist at the University of Calgary in Canada found the fossils while comparing Albertosaurus claws to other dinosaur species. Longrich then analyzed the fossils found in the Albertosaurus bonebed in Dry Island Provincial Park to find that they dated back 70 million years and represented a completely unknown species. Although fragments of Albertonykus had been discovered before, they had never been identified as a separate species. A chain of new discoveries found in Asia and South America exposed the existence of these previously unknown theropod dinosaurs.
show that they likely had long, slender snouts filled with tiny teeth similar to those of armadillos and anteaters. It is likely that Albertonykus ate insects, using its large thumb claw to tear open rotten logs to find its prey. As in other alvarezsaurs, the forelimbs of Albertonykus were specialized for digging, but were too short to permit burrowing. Unfortunately at this time the skeleton of Albertonykus is not complete, but its Mongolian relatives give us a distinct idea of what the rest of the skeleton would have looked like.
Possible prey items were evaluated and compared with the fossil record of social insects. Ant
s were not an important part of the ecosystem during the Cretaceous, and mound-building termites do not appear until the Eocene. This leaves the possibility that Albertonykus preyed on wood-nesting termites. This hypothesis was tested by examining petrified wood
from the Horseshoe Canyon Formation
, where Albertonykus was found. The wood found there frequently contains borings, which resemble those of termites.
and is one of only a few alvarezsaurid fossils that has been found outside of South America and Asia. After a phylogenetic analysis, it was shown that Albertonykus is the sister taxon of the Asian clade
Mononykinae, which supported the hypothesis that the alvarezsaurs originated in South America, and then dispersed to Asia through North America. The unearthing of Albertonykus provided important information into the biology of the Alvarezsauridae.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of alvarezsaurid dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from lower Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
-age (Upper Cretaceous) rocks of the Horseshoe Canyon Formation
Horseshoe Canyon Formation
The Horseshoe Canyon Formation is part of the Edmonton Group and is up to 230m in thickness. It is Late Campanian to Early Maastrichtian in age and is composed of mudstone, sandstone, and carbonaceous shales...
of Alberta, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. It is known from forelimb and hindlimb remains from multiple individuals. All but two of the specimens come from a bonebed dominated by Albertosaurus
Albertosaurus
Albertosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, more than 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which...
. Albertonykus is interpreted as having fed on wood-nesting termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
s because the forelimbs appear to be specialized for digging, but are too short for burrowing. Albertonykus is the earliest-known North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n alvarezsaurid; isolated remains of alvarezsaurids are known from later rock units in Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
and Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
(USA
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
).
The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is A. borealis, described by Nicholas Longrich and Philip Currie in a paper published in 2009 (which was available online as a preprint in 2008). The specific name (borealis) means "north".
Discovery
Until the 1900s it was unknown that dinosaurs like Albertonykus existed. In 1910, paleontologist Barnum BrownBarnum Brown
Barnum Brown , a paleontologist born in Carbondale, Kansas, and named after the circus showman P.T. Barnum, discovered the second fossil of Tyrannosaurus rex during a career that made him one of the most famous fossil hunters working from the late Victorian era into the early 20th century.Sponsored...
and his crew found a site filled with the bones of the tyrannosaur Albertosaurus sarcophagus
Albertosaurus
Albertosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, more than 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which...
. They unearthed the remains of at least nine different specimens of Albertosaurus in the single site, but stopped digging after just two weeks. The quarrying again produced the remains of over 20 specimens of Albertosaurus, and the quarry has yet to be fully excavated. It is not known why so many tyrannosaurs were found in one place: paleontologist Nick Longrich speculated that the site was part of a "predator trap", where food drew predators to their deaths. Close to a dozen arms and leg bones belonging to an unknown species of Albertosaurus were recovered in Alberta, Canada in 2002 by a team of scientist led by Philip J. Currie of the University of Alberta. The bones were then stored at the Royal Tyrrell Museum in Alberta.
In 2005 Nick Longrich, a paleontologist at the University of Calgary in Canada found the fossils while comparing Albertosaurus claws to other dinosaur species. Longrich then analyzed the fossils found in the Albertosaurus bonebed in Dry Island Provincial Park to find that they dated back 70 million years and represented a completely unknown species. Although fragments of Albertonykus had been discovered before, they had never been identified as a separate species. A chain of new discoveries found in Asia and South America exposed the existence of these previously unknown theropod dinosaurs.
Description
Albertonykus is the smallest known alvarezsaurid ever discovered in North America, measuring only 70 centimeters (2.5 ft) in length. Alvarezsaurs typically had slender hind legs, long rigid tails, and unusually short arms that were powerfully built to support a large claw. Although no skull bones of Albertonykus have been found, related animals from MongoliaMongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
show that they likely had long, slender snouts filled with tiny teeth similar to those of armadillos and anteaters. It is likely that Albertonykus ate insects, using its large thumb claw to tear open rotten logs to find its prey. As in other alvarezsaurs, the forelimbs of Albertonykus were specialized for digging, but were too short to permit burrowing. Unfortunately at this time the skeleton of Albertonykus is not complete, but its Mongolian relatives give us a distinct idea of what the rest of the skeleton would have looked like.
Possible prey items were evaluated and compared with the fossil record of social insects. Ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s were not an important part of the ecosystem during the Cretaceous, and mound-building termites do not appear until the Eocene. This leaves the possibility that Albertonykus preyed on wood-nesting termites. This hypothesis was tested by examining petrified wood
Petrified wood
Petrified wood is the name given to a special type of fossilized remains of terrestrial vegetation. It is the result of a tree having turned completely into stone by the process of permineralization...
from the Horseshoe Canyon Formation
Horseshoe Canyon Formation
The Horseshoe Canyon Formation is part of the Edmonton Group and is up to 230m in thickness. It is Late Campanian to Early Maastrichtian in age and is composed of mudstone, sandstone, and carbonaceous shales...
, where Albertonykus was found. The wood found there frequently contains borings, which resemble those of termites.
Classification
Albertonykus is a member of an unusual theropod group known as the AlvarezsauridaeAlvarezsauridae
Alvarezsauridae is an enigmatic family of small, long-legged running dinosaurs. Although originally thought to represent the earliest known flightless birds, a consensus of recent work suggests that they are primitive members of the Maniraptora. Other work found them to be the sister group to the...
and is one of only a few alvarezsaurid fossils that has been found outside of South America and Asia. After a phylogenetic analysis, it was shown that Albertonykus is the sister taxon of the Asian clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Mononykinae, which supported the hypothesis that the alvarezsaurs originated in South America, and then dispersed to Asia through North America. The unearthing of Albertonykus provided important information into the biology of the Alvarezsauridae.
External links
- Small 'Dr. Seuss'-like dinosaur dug up in Alberta news report at CBC.caCanadian Broadcasting CorporationThe Canadian Broadcasting Corporation, commonly known as CBC and officially as CBC/Radio-Canada, is a Canadian crown corporation that serves as the national public radio and television broadcaster...