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Bipedal dinosaur body mass estimation



Ben Creisler
bcreisler@gmail.com

A new online paper:

Nicolás E. Campione, David C. Evans, Caleb M. Brown and Matthew T.
Carrano (2014)
Body mass estimation in non-avian bipeds using a theoretical
conversion to quadruped stylopodial proportions.
Methods in Ecology and Evolution (advance online publication)
DOI: 10.1111/2041-210X.12226
http://onlinelibrary.wiley.com/doi/10.1111/2041-210X.12226/abstract

1. Body mass is strongly related to both physiological and ecological
properties of living organisms. As a result, generating robust,
broadly applicable models for estimating body mass in the fossil
record provides the opportunity to reconstruct palaeobiology and
investigate evolutionary ecology on a large temporal scale.

2. A recent study provided strong evidence that the minimum
circumference of stylopodial elements (humerus and femur) is
conservatively associated with body mass in living quadrupeds.
Unfortunately, this model is not directly applicable to extinct
bipeds, such as non-avian dinosaurs.

3. This study presents a new equation that mathematically corrects the
quadruped equation for use in bipeds. It is derived from the systemic
difference in the circumference-to-area scaling relationship of two
circles (hypothetical quadruped) and one circle (hypothetical biped),
which represent the cross-section of the main weight-bearing limb
bones.

4. When applied to a newly constructed dataset of femoral
circumferences and body masses in living birds, the new equation
reveals errors that are significantly lower than other published
equations, but significantly higher than the error inherent in the
avian dataset. Such errors, however, are expected given the unique
overall femoral circumference-body mass scaling relationship found in
birds.

5. Body mass estimates for a sample of bipedal dinosaurs using the new
model are consistent with recent estimates based on volumetric
life-reconstructions, but, in contrast, this equation is simpler to
use, with the concomitant potential to provide a wider set of body
mass estimates for extinct bipeds.

6. Although it is evident that no one estimation model is flawless,
the combined use of the corrected quadrupedal equations and the
previously published quadrupedal equation offer a consistent approach
with which to estimate body masses in both quadrupeds and bipeds.
These models have implications for conducting large-scale
macroevolutionary analyses of body size throughout the evolutionary
history of terrestrial vertebrates, and, in particular, across major
changes in body plan, such as the evolution of bipedality in
archosaurs and quadrupedality in dinosaurs.
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