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Limb morphometrics in Mesozoic theropods

Ben Creisler

A new online paper:

Brandon P. Hedrick, Phillip L. Manning, Eric R. Lynch, Samantha A.
Cordero and Peter Dodson (2014)
The geometry of taking flight: Limb morphometrics in Mesozoic theropods.
Journal of Morphology (advance online publication)
DOI: 10.1002/jmor.20329

Theropoda was one of the most successful dinosaurian clades during the
Mesozoic and has remained a dominant component of faunas throughout
the Cenozoic, with nearly 10,000 extant representatives. The discovery
of Archaeopteryx provides evidence that avian theropods evolved at
least 155 million years ago and that more than half of the tenure of
avian theropods on Earth was during the Mesozoic. Considering the
major changes in niche occupation for theropods resulting from the
evolution of arboreal and flight capabilities, we have analyzed
forelimb and hindlimb proportions among nonmaniraptoriform theropods,
nonavian maniraptoriforms, and basal avialans using reduced major axis
regressions, principal components analysis, canonical variates
analysis, and discriminant function analysis. Our study is the first
analysis on theropod limb proportions to apply phylogenetic
independent contrasts and size corrections to the data to ensure that
all the data are statistically independent and amenable to statistical
analyses. The three ordination analyses we performed did not show any
significant groupings or deviations between nonavian theropods and
Mesozoic avian forms when including all limb elements. However, the
bivariate regression analyses did show some significant trends between
individual elements that suggested evolutionary trends of increased
forelimb length relative to hindlimb length from nonmaniraptoriform
theropods to nonavian maniraptoriforms to basal avialans. The increase
in disparity and divergence away from the nonavian theropod body plan
is well documented within Cenozoic forms. The lack of significant
groupings among Mesozoic forms when examining the entire theropod body
plan concurrently suggests that nonavian theropods and avian theropods
did not substantially diverge in limb proportions until the Cenozoic.