Albertonykus

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Albertonykus
Temporal range: Late Cretaceous, 68.5  Ma
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Albertonykus borealis.jpg
Life restoration
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: Alvarezsauridae
Tribe: Mononykini
Genus: Albertonykus
Longrich & Currie, 2009
Species:
A. borealis
Binomial name
Albertonykus borealis
Longrich & Currie, 2009

Albertonykus (meaning "Alberta claw") is an alvarezsaurid dinosaur from the 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 , located at the top of Unit 4 of the Horseshoe Canyon Formation, [1] dating to ~68.5 million years ago. [2]

Contents

Albertonykus is interpreted as having fed on wood-nesting termites because the forelimbs appear specialized for digging, but are too short for burrowing. Albertonykus is the earliest-known North American alvarezsaurid. Isolated bones of alvarezsaurids are known from late Maastrichtian rocks in Montana and Wyoming (USA). The bones now belonged to a new genus, Trierarchuncus . [3] [4]

The type species is A. borealis, described by Nick Longrich and Philip Currie in 2009. The specific name (borealis) means "north". [5]

Discovery

Outcrops of the upper Horseshoe Canyon Formation in Dry Island Buffalo Jump Provincial Park, near the site of the Albertosaurus bonebed that produced Albertonykus Dry Island Buffalo Jump Horseshoe Canyon by Nick Longrich.jpg
Outcrops of the upper Horseshoe Canyon Formation in Dry Island Buffalo Jump Provincial Park, near the site of the Albertosaurus bonebed that produced Albertonykus

Until the 1990s it was unknown that dinosaurs like Albertonykus existed. A chain of new discoveries from Asia and South America exposed the existence of these previously unknown theropod dinosaurs. [6] North American finds remained rare. The bones of Albertonykus were discovered through a coincidental association with a much larger theropod dinosaur. In 1910, paleontologist Barnum Brown and his crew found a site filled with the bones of the gigantic tyrannosaurid 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. [7]

Renewed quarrying in the Albertosaurus bonebed in Dry Island Provincial Park again produced the remains of over twenty 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 trapped prey animals drew predators to their deaths. [7]

At the same site, over a dozen arm and leg bones belonging to an unknown species of small theropod were in 2002 excavated by a team of scientist led by Philip John Currie of the University of Alberta. The bones were then stored at the Royal Tyrrell Museum in Alberta. [8] [9] In 2005 Nick Longrich, then a student at the University of Calgary , happened upon the small fossils while comparing Albertosaurus claws to other dinosaur species. Longrich recognized the fossils as alvarezsaurid, concluding that they represented a new species. [8] [9] Other fragments of Albertonykus were then recognized in the collections, which had not been identified as a separate species. [6]

Description

Albertonykus borealis foraging for termites Albertonykus borealis by Nick Longrich.jpg
Albertonykus borealis foraging for termites

Albertonykus is the smallest known alvarezsauridae ever discovered in North America, measuring 1.1 m (3.6 ft) long and weighing 5 kg (11 lb). [10] 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. [7] It is likely that Albertonykus ate insects, using its large thumb claw to tear open rotten logs to find its prey. [8] 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. [7]

Possible prey items were evaluated and compared with the fossil record of social insects. 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.

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. [8] After a phylogenetic analysis, it was shown that Albertonykus is a member of the Asian clade Mononykini, 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.

Related Research Articles

<i>Albertosaurus</i> Genus of bipedal predatory dinosaur

Albertosaurus is a genus of large tyrannosaurid theropod dinosaur that lived in northwestern North America during the early to middle Maastrichtian age of the Late Cretaceous period, about 71 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which the genus is named, although an indeterminate species has been discovered in the Corral de Enmedio and Packard Formations of Mexico. Scientists disagree on the content of the genus and some recognize Gorgosaurus libratus as a second species.

<i>Daspletosaurus</i> Genus of tyrannosaurid dinosaur from Late Cretaceous period

Daspletosaurus is a genus of tyrannosaurid dinosaur that lived in Laramidia between about 78 and 74.4 million years ago, during the Late Cretaceous Period. The genus Daspletosaurus contains three named species. Fossils of the earlier type species, D. torosus, have been found in Alberta, while fossils of a later species, D. horneri, have been found only in Montana. D. wilsoni has been suggested as an intermediate species between D. torosus and D. horneri that evolved through anagenesis, but this theory has been disputed by other researchers.

<i>Dromaeosaurus</i> Extinct genus of dinosaurs

Dromaeosaurus is a genus of dromaeosaurid theropod dinosaur that lived during the Late Cretaceous period, sometime between 80 and 69 million years ago, in Alberta, Canada and the western United States. The type species is Dromaeosaurus albertensis, which was described by William Diller Matthew and Barnum Brown in 1922. Its fossils were unearthed in the Hell Creek Formation, Horseshoe Canyon Formation and Dinosaur Park Formation. Teeth attributed to this genus have been found in the Prince Creek Formation. Dromaeosaurus is the type genus of both Dromaeosauridae and Dromaeosaurinae, which include many genera with similar characteristics to Dromaeosaurus such as possibly its closest relative Dakotaraptor. Dromaeosaurus was heavily built, more so than other dromaeosaurs that are similar in size, like Velociraptor.

<i>Shuvuuia</i> Extinct family of bird-like dinosaurs

Shuvuuia is a genus of bird-like theropod dinosaur from the late Cretaceous period of Mongolia. It is a member of the family Alvarezsauridae, small coelurosaurian dinosaurs which are characterized by short but powerful forelimbs specialized for digging. The type species is Shuvuuia deserti, or "desert bird". The name Shuvuuia is derived from the Mongolian word shuvuu (шувуу) meaning "bird".

<i>Parvicursor</i> Extinct genus of dinosaurs

Parvicursor is a genus of tiny maniraptoran dinosaur with long slender legs for fast running.

<span class="mw-page-title-main">Alvarezsauridae</span> Family of extinct long-legged dinosaurs

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 specialized. They had tiny but stout forelimbs, with compact, bird-like hands. Their skeletons suggest that they had massive breast and arm muscles, possibly adapted for digging or tearing. They had long, tube-shaped snouts filled with tiny teeth. They have been interpreted as myrmecophagous, adapted to prey on colonial insects such as termites, with the short arms acting as effective digging instruments to break into nests.

<i>Gorgosaurus</i> Genus of tyrannosaur dinosaur

Gorgosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.5 and 75 million years ago. Fossil remains have been found in the Canadian province of Alberta and the U.S. state of Montana. Paleontologists recognize only the type species, G. libratus, although other species have been erroneously referred to the genus.

<span class="mw-page-title-main">Ornithomimosauria</span> Extinct clade of theropod dinosaurs

Ornithomimosauria 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, as well as Africa and possibly Australia. The group first appeared in the Early Cretaceous and persisted until the Late Cretaceous. Primitive members of the group include Nqwebasaurus, Pelecanimimus, Shenzhousaurus, Hexing and Deinocheirus, the arms of which reached 2.4 m (8 feet) in length. More advanced species, members of the family Ornithomimidae, include Gallimimus, Struthiomimus, and Ornithomimus. Some paleontologists, like Paul Sereno, consider the enigmatic alvarezsaurids to be close relatives of the ornithomimosaurs and place them together in the superfamily Ornithomimoidea.

<i>Pachyrhinosaurus</i> Ceratopsid dinosaur genus from Late Cretaceous US and Canada

Pachyrhinosaurus is an extinct genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in Alberta, Canada, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species have been found in Alberta and Alaska. A great number were not available for study until the 1980s, resulting in a relatively recent increase of interest in Pachyrhinosaurus.

<i>Atrociraptor</i> Extinct genus of dinosaurs

Atrociraptor is a genus of saurornitholestine dromaeosaurid theropod dinosaur from the Late Cretaceous of Alberta, Canada.

<i>Anchiceratops</i> Extinct genus of dinosaurs

Anchiceratops is an extinct genus of chasmosaurine ceratopsid dinosaur that lived approximately 72 to 71 million years ago during the latter part of the Cretaceous Period in what is now Alberta, Canada. Anchiceratops was a medium-sized, heavily built, ground-dwelling, quadrupedal herbivore that could grow up to an estimated 4.3 metres (14 ft) long. Its skull featured two long brow horns and a short horn on the nose. The skull frill was elongated and rectangular, its edges adorned by coarse triangular projections. About a dozen skulls of the genus have been found.

<i>Chirostenotes</i> Extinct genus of dinosaurs

Chirostenotes is a genus of oviraptorosaurian dinosaur from the late Cretaceous of Alberta, Canada. The type species is Chirostenotes pergracilis.

<i>Montanoceratops</i> Extinct genus of dinosaurs

Montanoceratops is an extinct genus of small ceratopsian dinosaur that lived approximately 70 million years ago during the latter part of the Cretaceous Period in what is now Montana and Alberta. Montanoceratops was a small sized, moderately-built, ground-dwelling, quadrupedal herbivore, that could grow up to an estimated 2.5 m (8.2 ft) in length and 170 kg (370 lb) in body mass.

<i>Mononykus</i> Extinct genus of dinosaurs

Mononykus is a genus of alvarezsaurid dinosaur that lived during the Late Cretaceous in what is now Asia on the Nemegt Formation, about 70 million years ago.

<i>Patagonykus</i> Extinct genus of dinosaurs

Patagonykus is a genus of theropod dinosaur from the Upper Cretaceous of Argentina. This alvarezsauroid was discovered in exposures of the Portezuelo Formation (Turonian-Coniacian) of the Rio Neuquén Subgroup in the Neuquén Basin, Neuquen Province of Patagonia, Argentina. The holotype consists of an incomplete but well-preserved skeleton, lacking a skull, but including many vertebrae, the coracoids, a partial forelimb, pelvic girdle, and hindlimbs. Patagonykus has been classed with the Alvarezsauridae, a family which includes such taxa as the Mongolian Mononykus and the Argentinian Alvarezsaurus. In 2010 Gregory S. Paul estimated its length at 1 meter and its weight at 3.5 kg.

<span class="mw-page-title-main">Horseshoe Canyon Formation</span> Geological formation in Canada

The Horseshoe Canyon Formation is a stratigraphic unit of the Western Canada Sedimentary Basin in southwestern Alberta. It takes its name from Horseshoe Canyon, an area of badlands near Drumheller.

<span class="mw-page-title-main">Alvarezsauroidea</span> Extinct superfamily of dinosaurs

Alvarezsauroidea is a group of small maniraptoran dinosaurs. Alvarezsauroidea, Alvarezsauridae, and Alvarezsauria are named for the historian Gregorio Álvarez, not the more familiar physicist Luis Alvarez, or his son geologist Walter Alvarez who jointly proposed that the Cretaceous–Paleogene extinction event was caused by an impact event. The group was first formally proposed by Choiniere and colleagues in 2010, to contain the family Alvarezsauridae and non-alvarezsaurid alvarezsauroids, such as Haplocheirus, which is the basalmost of the Alvarezsauroidea. The discovery of Haplocheirus extended the stratigraphic evidence for the group Alvarezsauroidea about 63 million years further in the past. The division of Alvarezsauroidea into the Alvarezsauridae and the non-alvarezsaurid alvarezsauroids is based on differences in their morphology, especially in their hand morphology.

Xixianykus is a genus of alvarezsaurid theropod dinosaur from the late Cretaceous period of China. Known from a slab of rock which contains a partial postcranial skeleton unearthed in the Late Cretaceous (Coniacian-Santonian) Majiacun Formation of the Xixia Basin in Henan, China.

<i>Nemegtonykus</i> Extinct genus of dinosaurs

Nemegtonykus is a genus of alvarezsaurid dinosaur from the Nemegt Formation in Mongolia. The type and only species is Nemegtonykus citus. It is the second alvarezsaur known from the Nemegt Formation, the other being Mononykus.

<i>Trierarchuncus</i> Extinct genus of reptiles

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. 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.

References

  1. Larson, D. W., Brinkman, D. B., & Bell, P. R. (2010). Faunal assemblages from the upper Horseshoe Canyon Formation, an early Maastrichtian cool-climate assemblage from Alberta, with special reference to the Albertosaurus sarcophagus bonebed This article is one of a series of papers published in this Special Issue on the theme Albertosaurus. Canadian Journal of Earth Sciences, 47(9), 1159-1181.
  2. Arbour, Victoria (2010). "A Cretaceous armoury: Multiple ankylosaurid taxa in the Late Cretaceous of Alberta, Canada and Montana, USA". Journal of Vertebrate Paleontology. 30 (Supplement 2): 55A. doi:10.1080/02724634.2010.10411819.
  3. 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. 116: Article 104560. doi: 10.1016/j.cretres.2020.104560 . S2CID   225630913.
  4. "Badlands - Research - 2020 new alvarezsaurid species". Dickinson Museum Center. Retrieved 2020-07-17.
  5. Longrich, Nicholas R.; Currie, Philip J. (2009). "Albertonykus borealis, a new alvarezsaur (Dinosauria: Theropoda) from the Early Maastrichtian of Alberta, Canada: Implications for the systematics and ecology of the Alvarezsauridae". Cretaceous Research. 30 (1): 239–252. doi:10.1016/j.cretres.2008.07.005.
  6. 1 2 Brian Switek, Smithsonian Magazine, http://dinosaur.smithsonianmag.com/2008/10/06/a-dinosaur-that-ate-termites-for-breakfast/ Archived 2008-10-14 at the Wayback Machine
  7. 1 2 3 4 Nick Longrich, University of Calgary, "Albertonykus borealis". Archived from the original on 2009-03-22. Retrieved 2008-10-29.
  8. 1 2 3 4 Ken Than, National Geographic News,
  9. 1 2 Jeanna Bryner, MSNBC.com,
  10. Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs (2nd ed.). Princeton, New Jersey: Princeton University Press. p. 137. ISBN   9780691167664.