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Taxonomic status of Nedoceratops hatcheri (and Torosaurus latus)



Dear DMLers,
as far as I know, this paper hasn't been mantioned yet. It was
published yesterday.

Farke, A. A. 2011. Anatomy and Taxonomic Status of the Chasmosaurine
Ceratopsid Nedoceratops hatcheri from the Upper Cretaceous Lance
Formation of Wyoming, U.S.A. PLoS ONE 6(1): e16196.
http://dx.doi.org/10.1371/journal.pone.0016196

Background
The validity of Nedoceratops hatcheri, a chasmosaurine ceratopsid
dinosaur known from a single skull recovered in the Lance Formation of
eastern Wyoming, U.S.A., has been debated for over a century. Some
have argued that the taxon is an aberrant Triceratops, and most
recently it was proposed that N. hatcheri represents an intermediate
ontogenetic stage between “young adult” and “old adult” forms of a
single taxon previously split into Triceratops and Torosaurus.

Methodology/Principal Findings
The holotype skull of Nedoceratops hatcheri was reexamined in order to
map reconstructed areas and compare the specimen with other
ceratopsids. Although squamosal fenestrae are almost certainly not of
taxonomic significance, some other features are unique to N. hatcheri.
These include a nasal lacking a recognizable horn, nearly vertical
postorbital horncores, and relatively small parietal fenestrae. Thus,
N. hatcheri is tentatively considered valid, and closely related to
Triceratops spp. The holotype of N. hatcheri probably represents an
“old adult,” based upon bone surface texture and the shape of the
horns and epiossifications on the frill. In this study, Torosaurus is
maintained as a genus distinct from Triceratops and Nedoceratops.
Synonymy of the three genera as ontogenetic stages of a single taxon
would require cranial changes otherwise unknown in ceratopsids,
including additions of ossifications to the frill and repeated
alternation of bone surface texture between juvenile and adult
morphotypes.

Conclusions/Significance
Triceratops, Torosaurus, and likely Nedoceratops, are all distinct
taxa, indicating that species richness for chasmosaurine ceratopsids
in the Lance Formation just prior to the Cretaceous-Paleocene
extinction was roughly equivalent to that earlier in the Cretaceous.

Best,
--
Daniel Madzia
web: www.wildprehistory.org
mail: daniel.madzia@gmail.com
skype: danielmadzia