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Body mass and limb bone scaling in dinosaurs and other quadrupeds



From: Ben Creisler
bcreisler@gmail.com


A new paper. The pdf is Open Access.

Nicolás E. Campione and David C. Evans (2012)
A universal scaling relationship between body mass and proximal limb
bone dimensions in quadrupedal terrestrial tetrapods.
BMC Biology 10(1): 60
DOI: 10.1186/1741-7007-10-60Open Access
http://www.springerlink.com/content/q377611126317173/


Background
Body size is intimately related to the physiology and ecology of an
organism. Therefore, accurate and consistent body mass estimates are
essential for inferring numerous aspects of paleobiology in extinct
taxa, and investigating large-scale evolutionary and ecological
patterns in the history of life. Scaling relationships between
skeletal measurements and body mass in birds and mammals are commonly
used to predict body mass in extinct members of these crown clades,
but the applicability of these models for predicting mass in more
distantly related stem taxa, such as non-avian dinosaurs and
non-mammalian synapsids, has been criticized on biomechanical grounds.
Here we test the major criticisms of scaling methods for estimating
body mass using an extensive dataset of mammalian and non-avian
reptilian species derived from individual skeletons with live weights.

Results
Significant differences in the limb scaling of mammals and reptiles
are noted in comparisons of limb proportions and limb length to body
mass. Remarkably, however, the relationship between proximal
(stylopodial) limb bone circumference and body mass is highly
conserved in extant terrestrial mammals and reptiles, in spite of
their disparate limb postures, gaits, and phylogenetic histories. As a
result, we are able to conclusively reject the main criticisms of
scaling methods that question the applicability of a universal scaling
equation for estimating body mass in distantly related taxa.

Conclusions
The conserved nature of the relationship between stylopodial
circumference and body mass suggests that the minimum diaphyseal
circumference of the major weight-bearing bones is only weakly
influenced by the varied forces exerted on the limbs (that is,
compression or torsion) and most strongly related to the mass of the
animal. Our results, therefore, provide a much-needed, robust,
phylogenetically corrected framework for accurate and consistent
estimation of body mass in extinct terrestrial quadrupeds, which is
important for a wide range of paleobiological studies (including
growth rates, metabolism, and energetics) and meta-analyses of body
size evolution.