[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Nedoceratops as growth stage between Triceratops and "Torosaurus"
From: Ben Creisler
New in PLoS ONE:
Scannella, J.B. & Horner, J.R. (2011)
‘Nedoceratops’: An Example of a Transitional Morphology.
PLoS ONE 6(12): e28705.
The holotype and only specimen of the chasmosaurine ceratopsid dinosaur
‘Nedoceratops hatcheri’ has been the source of considerable taxonomic debate
since its initial description. At times it has been referred to its own genus
while at others it has been considered synonymous with the contemporaneous
chasmosaurine Triceratops. Most recently, the debate has focused on whether the
specimen represents an intermediate ontogenetic stage between typical young
adult Triceratops and the proposed mature morphology, which was previously
considered to represent a distinct genus, ‘Torosaurus’.
The only specimen of ‘Nedoceratops hatcheri’ was examined and the proposed
diagnostic features of this taxon were compared with other chasmosaurine
ceratopsids. Every suggested autapomorphy of ‘Nedoceratops’ is found in
specimens of Triceratops. In this study, Triceratops includes the adult
‘Torosaurus’ morphology. The small parietal fenestra and elongate squamosals of
Nedoceratops are consistent with a transition from a short, solid
parietal-squamosal frill to an expanded, fenestrated condition. Objections to
this hypothesis regarding the number of epiossifications of the frill and
alternations of bone surface texture were explored through a combination of
comparative osteology and osteohistology. The synonymy of the three taxa was
further supported by these investigations.
The Triceratops, ‘Torosaurus’, and ‘Nedoceratops’ morphologies represent
ontogenetic variation within a single genus of chasmosaurine: Triceratops. This
study highlights how interpretations of dinosaur paleobiology, biodiversity,
and systematics may be affected by ascribing o