Albertonykus

Albertonykus Temporal range: Late Cretaceous, 68.5Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Life restoration
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Suborder:	Theropoda
Family:	†Alvarezsauridae
Subfamily:	†Parvicursorinae
Tribe:	†Mononykini
Genus:	†Albertonykus Longrich & Currie, 2009
Species:	† A. borealis
Binomial name
Albertonykus borealis Longrich & Currie, 2009

Albertonykus (meaning "Alberta claw") is a genus of alvarezsaurid dinosaur from 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. This bonebed is located at the top of Unit 4 of the Horseshoe Canyon Formation,^[1] which dates to about 68.5 million years ago.^[2] Albertonykus is interpreted as having fed on wood-nesting termites because the forelimbs appear to be specialized for digging, but are too short for burrowing. Albertonykus is the earliest-known North American alvarezsaurid; isolated remains of alvarezsaurids are known from later rock units in Montana and Wyoming (USA).^[3]

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".^[3]

Discovery

Until the 1900s it was unknown that dinosaurs like Albertonykus existed.^[4] In 1910, paleontologist Barnum Brown 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.^[5] 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.^[5] 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.^[6][7]

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.^[6][7][8] 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.^[4]

Description

Albertonykus is the smallest known alvarezsaurid ever discovered in North America, measuring only 70 centimeters (2.5 ft) in length.^[6] 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 Mongolia show that they likely had long, slender snouts filled with tiny teeth similar to those of armadillos and anteaters.^[5] It is likely that Albertonykus ate insects, using its large thumb claw to tear open rotten logs to find its prey.^[6] As in other alvarezsaurs, the forelimbs of Albertonykus were specialized for digging, but were too short to permit burrowing.^[8] 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.^[5] s. Ants 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.^[8]

s. Ants 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.^[8]

Classification

Albertonykus is a member of an unusual theropod group known as the Alvarezsauridae and is one of only a few alvarezsaurid fossils that has been found outside of South America and Asia.^[6] 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.

References

External links

• Small 'Dr. Seuss'-like dinosaur dug up in Alberta news report at CBC.ca