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Ceratopsid lower jaw shape and mechanics

Ben Creisler

A new online paper:

Leonardo Maiorino, Andrew A. Farke, Tassos Kotsakis, Luciano Teresi
and Paolo Piras (2015)
Variation in the shape and mechanical performance of the lower jaws in
ceratopsid dinosaurs (Ornithischia, Ceratopsia).
Journal of Anatomy (advance online publication)
DOI: 10.1111/joa.12374

Ceratopsidae represents a group of quadrupedal herbivorous dinosaurs
that inhabited western North America and eastern Asia during the Late
Cretaceous. Although horns and frills of the cranium are highly
variable across species, the lower jaw historically has been
considered to be relatively conservative in morphology. Here, the
lower jaws from 58 specimens representing 21 ceratopsoid taxa were
sampled, using geometric morphometrics and 2D finite element analysis
(FEA) to explore differences in morphology and mechanical performance
across Ceratopsoidea (the clade including Ceratopsidae, Turanoceratops
and Zuniceratops). Principal component analyses and non-parametric
permuted manovas highlight Triceratopsini as a morphologically
distinct clade within the sample. A relatively robust and elongate
dentary, a larger and more elongated coronoid process, and a small and
dorso-ventrally compressed angular characterize this clade, as well as
the absolutely larger size. By contrast, non-triceratopsin
chasmosaurines, Centrosaurini and Pachyrhinosaurini have similar
morphologies to each other. Zuniceratops and Avaceratops are distinct
from other taxa. No differences in size between Pachyrhinosaurini and
Centrosaurini are recovered using non-parametric permuted anovas.
Structural performance, as evaluated using a 2D FEA, is similar across
all groups as measured by overall stress, with the exception of
Triceratopsini. Shape, size and stress are phylogenetically
constrained. A longer dentary as well as a long coronoid process
result in a lower jaw that is reconstructed as relatively much more
stressed in triceratopsins.