Judiceratops (Upper Cretaceous ceratopsian from Montana) reassessed

[Ben Creisler <bcreisler@gmail.com>]

Ben Creisler
bcreisler@gmail.com

A new online paper:

James Alexander Campbell (2014)
A reassessment of the horned dinosaur Judiceratops tigris
(Ornithischia: Ceratopsidae) from the Upper Cretaceous (Campanian) of
Montana, U.S.A.
Canadian Journal of Earth Sciences (advance online publication)
doi: 10.1139/cjes-2014-0172
http://www.nrcresearchpress.com/doi/abs/10.1139/cjes-2014-0172?src=recsys#.VIPFcjHF_To

Judiceratops tigris is a recently described ceratopsid, collected from
sediments of the Upper Cretaceous (middle Campanian) Judith River
Formation (JRF) of northern Montana, U.S.A. The current diagnosis for
this taxon is tentative, as it is based on four fragmentary cranial
specimens that have limited anatomical overlap. Although these four
specimens were not found associated, they were all collected from the
same localized area (Kennedy Coulee). New observations,
interpretations, and reconstructions of J. tigris are presented in
this study, based on the original assumption that these specimens
represent the same taxon. Based on these findings, J. tigris had:
elongate postorbital horncores with an autapomorphic ovate
(egg-shaped) cross section; squamosals with non-imbricated
episquamosals, and an anterolaterally-oriented anteriormost
episquamosal; a wide medial parietal bar with an autapomorphic
meniscus-shaped cross section; an anteroposteriorly wide posterior
parietal bar, and, consequently, reduced parietal fenestrae; and at
least four small, low-lying epiparietals on each side of the frill. A
phylogenetic analysis incorporating the revised diagnosis of J. tigris
supports the previous referral of this taxon to Chasmosaurinae, but
missing anatomy prevents an understanding of how J. tigris is related
to other chasmosaurines. Judiceratops tigris is retained here as a
distinct taxon, and, hence, the oldest known chasmosaurine, but has
more in common with other chasmosaurines than was previously thought.
Further fossil collecting in the JRF of Montana may produce more
complete specimens of J. tigris and provide a means of testing the new
reconstructions presented here.