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Acheroraptor, new dromaeosaurid theropod from Late Cretaceous of Montana

From: Ben Creisler

A new online paper:

David C. Evans, Derek W. Larson & Philip J. Currie (2013)
A new dromaeosaurid (Dinosauria: Theropoda) with Asian affinities from
the latest Cretaceous of North America.
Naturwissenschaften (advance online publication)
DOI: 10.1007/s00114-013-1107-5

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. 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.