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Arrhinoceratops (ceratopsian from Alberta), new information



From: Ben Creisler
bcreisler@gmail.com


A new online paper:

Jordan Mallon, Robert Holmes, Jason Anderson, Andrew Farke & David C
Evans (2014)
New Information on the Rare Horned Dinosaur Arrhinoceratops brachyops
(Ornithischia: Ceratopsidae) from the Upper Cretaceous of Alberta,
Canada.
Canadian Journal of Earth Sciences (advance online publication)
doi: 10.1139/cjes-2014-0028
http://www.nrcresearchpress.com/doi/abs/10.1139/cjes-2014-0028#.U2j4OfldXeI


Arrhinoceratops brachyops is a poorly understood chasmosaurine
ceratopsid from the Upper Cretaceous Horseshoe Canyon Formation of
Alberta, previously described on the basis of only a single skull.
Here, we report on a second specimen attributable to this species,
including a relatively complete skull, syncervical, and partial left
forelimb. This second specimen clarifies aspects of morphology not
visible in the holotype, and also elucidates variation in A.
brachyops. The species is distinguished by a square-shaped triangular
process of the premaxilla, a steeply inclined triturating surface of
the predentary, and a triangular nasal horncore in horizontal section.
The dentary is also distinctive in bearing a bony lateral ridge
similar to that of Anchiceratops ornatus, but more strongly developed.
Phylogenetic analysis cannot resolve the relationships of
Arrhinoceratops beyond the level of Chasmosaurinae, owing to both
missing data and conflicting characters. However, we do find some
support for a deep split within Chasmosaurinae, contrary to
conventional topologies. We also report on other fragmentary specimens
plausibly attributable to A. brachyops that suggest a minimum age
range of approximately 750 Kyr for this species.