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Dinosaur body size distribution

From: Ben Creisler

New in PLoS ONE:

Eoin J. O’Gorman & David W. E. Hone (2012)
Body Size Distribution of the Dinosaurs.
PLoS ONE 7(12): e51925.

The distribution of species body size is critically important for
determining resource use within a group or clade. It is widely known
that non-avian dinosaurs were the largest creatures to roam the Earth.
There is, however, little understanding of how maximum species body
size was distributed among the dinosaurs. Do they share a similar
distribution to modern day vertebrate groups in spite of their large
size, or did they exhibit fundamentally different distributions due to
unique evolutionary pressures and adaptations? Here, we address this
question by comparing the distribution of maximum species body size
for dinosaurs to an extensive set of extant and extinct vertebrate
groups. We also examine the body size distribution of dinosaurs by
various sub-groups, time periods and formations. We find that
dinosaurs exhibit a strong skew towards larger species, in direct
contrast to modern day vertebrates. This pattern is not solely an
artefact of bias in the fossil record, as demonstrated by contrasting
distributions in two major extinct groups and supports the hypothesis
that dinosaurs exhibited a fundamentally different life history
strategy to other terrestrial vertebrates. A disparity in the size
distribution of the herbivorous Ornithischia and Sauropodomorpha and
the largely carnivorous Theropoda suggests that this pattern may have
been a product of a divergence in evolutionary strategies: herbivorous
dinosaurs rapidly evolved large size to escape predation by carnivores
and maximise digestive efficiency; carnivores had sufficient resources
among juvenile dinosaurs and non-dinosaurian prey to achieve optimal
success at smaller body size.