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New Hell Creek Dromaeosaurid Described

December 16, 2013
Holotype maxilla and associated dentary of Acheroraptor temertyorum. Copyright Royal Ontario Museum.

Holotype maxilla and associated dentary of Acheroraptor temertyorum. Copyright Royal Ontario Museum.

Today we formally announced publication of a new species of a small, meat-eating dinosaur (‘raptor’) based on newly discovered fossils from Montana, USA. Acheroraptor temertyorum is based on associated upper and lower jaw fossils from the Hell Creek Formation of Montana. It was relatively large for a “raptor”, approaching Deinonychus in size, with a long-snouted skull and dagger-like ridged teeth.

Acheroraptor was one of the last non-avian dinosaurs. It lived 67 to 66 million years ago in western North America, in a community that included Tyrannosaurus rex and  Triceratops. As such, Acheroraptor gives us a more complete picture of the ecosystem in North America just before the great extinction that marked the end of the Age of Dinosaurs.

The unique ridged teeth of Acheroraptor have been recognized for decades, but the lack of reasonably complete diagnostic material did not permit determination of the taxonomic affinities and evolutionary relationships of the Hell Creek dromaeosaur until now.  Interestingly, the jaw bones of Acheroraptor compare more closely to those of Velociraptor and other long-snouted Asian species than those of older North American species. Dromaeosaurid evolutionary relationships and biogeography will continue to be contentious. Phylogenetic analysis based on the dataset of Longrich and Currie (2009) recovered Acheroraptor as a velociraptorine dromaeosaurid, nested within a group of Asian species. The close evolutionary relationship of Acheroraptor to a  group of late-occurring Asian species that includes Velociraptor suggests that migration from Asia may have continued to shape North American dinosaur communities right up until the end of the Cretaceous period.

The research describing Acheroraptor was published in the latest issue of Naturwissenschaften:

Evans, D. C.,  D. Larson, and P. J. Currie. 2013. A new dromaeosaurid (Dinosauria: Theropoda) with Asian Affinities from the latest Cretaceous of North America. Naturwissenschaften 100 (11): 1041-1049. Available online here.

The Press Release from the Royal Ontario Museum can be found here.

Two Acheroraptor feeding at a Triceratops carcass as Tyrannosaurus rex approaches. Courtesy of Julius Csotonyi .

Two Acheroraptor feeding at a Triceratops carcass as Tyrannosaurus rex approaches. Courtesy of Julius Csotonyi .

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One Comment leave one →
  1. December 22, 2013 1:12 PM

    Fascinating and cool! Please check out my article and drawing of Acheroraptor on my history / paleontology blog “Dinosaurs and Barbarians”.

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