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Chasmosaurus revision

From: Ben Creisler

New paper online in Zootaxa:

Susannah C.R.Maidment & Paul M. Barrett (2011)
A new specimen of Chasmosaurus belli (Ornithischia: Ceratopsidae), a
revision of the genus, and the utility of postcrania in the taxonomy and
systematics of ceratopsid dinosaurs.
Zootaxa 2963: 1?47 (12 Jul. 2011)
Preview first page:

A previously undescribed chasmosaurine specimen excavated in 1919?1920 by
William Cutler from the Dinosaur Park Formation of Alberta, Canada is
referable to Chasmosaurus belli. The specimen comprises an almost complete
skull in which, uniquely among Chasmosaurus, the cranial elements are
disarticulated, allowing detailed examination of their morphology for the
first time. The complete braincase is present and allows comparison with
the braincase of other ceratopsians. The specimen also preserves an
uncrushed and undistorted postcranium, including cervical, dorsal and
sacral vertebrae and limb elements. The vertebral column of Chasmosaurus
has never previously been described in detail, and NHMUK R4948 affords the
opportunity to examine it because of the unparalleled state of vertebral
preservation. A proliferation of new chasmosaurine genera has recently been
described; many of them differ from each other only in details of frill and
epiparietal morphology. Several of these are based on specimens previously
referred to Chasmosaurus. As a result, the characters that distinguish
Chasmosaurus from other Campanian chasmosaurines are unclear. However, the
genus Chasmosaurus and species within the genus are diagnosable and valid
based on unique combinations of characters and frill morphology. Detailed
examination of the postcranial morphology of a variety of centrosaurines
and chasmosaurines has highlighted previously undescribed synapomorphies
for the two major ceratopsid clades, concentrated in the pectoral girdle
and forelimb. Inconsistencies in the vertebral formula of specimens
referred to Chasmosaurus belli suggests that the postcrania of ceratopsids
may vary between species and genera far more than previously thought, and
that postcranial characters should be incorporated into phylogenetic and
taxonomic studies. 

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