A new dromaeosaurid (Dinosauria: Theropoda) with Asian affinities from the latest Cretaceous of North America
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ORIGINAL PAPER
A new dromaeosaurid (Dinosauria: Theropoda) with Asian affinities from the latest Cretaceous of North America David C. Evans & Derek W. Larson & Philip J. Currie
Received: 1 March 2013 / Revised: 10 August 2013 / Accepted: 14 August 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Dromaeosaurids from the Maastrichtian of North America have a poor fossil record and are known largely from isolated teeth, which have typically been referred to taxa based on more complete material from earlier Campanian strata. An almost complete maxilla with well-preserved dentition and an associated dentary from the Hell Creek Formation of Montana are used to establish a new dromaeosaurid taxon in the latest Maastrichtian, immediately prior to the end-Cretaceous extinction event. Acheroraptor temertyorum gen. et sp. nov. is differentiated from other dromaeosaurids on the basis of a hypertrophied postantral wall that projects posteriorly into the antorbital fenestra, a maxillary fenestra positioned low in the antorbital fossa and directly posterior to the promaxillary fenestra, and distinctive dentition with marked apicobasal ridges. The new material allows a dromaeosaurid from the Maastrichtian of North America to be placed within a phylogenetic framework for the first time. Phylogenetic analysis suggests Acheroraptor is a velociraptorine that is more closely related to Asian dromaeosaurids, including Tsaagan and Velociraptor, than it is to Dromaeosaurus , Saurornitholestes, or any other taxon from North America. Communicated by: Robert Reisz Electronic supplementary material The online version of this article (doi:10.1007/s00114-013-1107-5) contains supplementary material, which is available to authorized users. D. C. Evans (*) Department of Natural History, Royal Ontario Museum, 100 Queen’s Park, Toronto, Ontario M5S 2C6, Canada e-mail: [email protected] D. C. Evans : D. W. Larson Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2, Canada P. J. Currie Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
As part of the Lancian Tyrannosaurus–Triceratops fauna, A. temertyorum is the latest occurring dromaeosaurid. Its relationships and occurrence suggest a complex historical biogeographic scenario that involved multiple, bi-directional faunal interchanges between Asia and North America during the Late Cretaceous. Keywords Dromaeosauridae . Theropoda . Cretaceous . Biogeography
Introduction Dromaeosaurids are a group of carnivorous theropods notable for their close phylogenetic relationship to Aves. Although dromaeosaurids can be inferred to have originated sometime prior to the Late Jurassic, their fossil record is largely restricted to the Cretaceous (Norell and Makovicky 2004; Turner et al. 2012). Dromaeosaurids had a global distribution during the Late Cretaceous, but their fossil record for this time is generally poor. Despite over a century of sustained collecting, dromaeosaurids from North America r
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