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Albertonykus
''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,〔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.〕 which dates to about 68.5 million years ago. ''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).
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".〔
==Discovery==
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.〔Brian Switek, ''Smithsonian Magazine'',http://dinosaur.smithsonianmag.com/2008/10/06/a-dinosaur-that-ate-termites-for-breakfast/〕 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.〔Nick Longrich, ''University of Calgary'',http://www.ucalgary.ca/~longrich/Albertonykus%20borealis.html〕 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 food drew predators to their deaths.〔 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.〔Ken Than, ''National Geographic News'',http://news.nationalgeographic.com/news/2008/09/080925-smallest-dinosaur.html〕〔Jeanna Bryner, ''MSNBC.com'',http://www.msnbc.msn.com/id/26856262/〕
In 2005 Nick Longrich, a paleontologist at the University of Calgary in Canada, happened upon the small fossils while comparing ''Albertosaurus'' claws to other dinosaur species. Longrich then analyzed the remains, concluding that they represented a previously unknown species.〔〔〔N.R. Longrich, ''DinoNews'',http://www.dinodata.org/index.php?option=com_content&task=view&id=9909&Itemid=103〕 Although fragments of ''Albertonykus'' had been discovered before, they had never been identified as a separate species.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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