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Downsizing Dreadnoughtus body mass (free pdf)

Ben Creisler

A new paper in open access:

Karl T. Bates, Peter L. Falkingham, Sophie Macaulay, Charlotte Brassey
& Susannah C. R. Maidment (2015)
Downsizing a giant: re-evaluating Dreadnoughtus body mass.
Biology Letters 11: 20150215.
DOI: 10.1098/rsbl.2015.0215

Estimates of body mass often represent the founding assumption on
which biomechanical and macroevolutionary hypotheses are based.
Recently, a scaling equation was applied to a newly discovered
titanosaurian sauropod dinosaur (Dreadnoughtus), yielding a 59 300 kg
body mass estimate for this animal. Herein, we use a modelling
approach to examine the plausibility of this mass estimate for
Dreadnoughtus. We find that 59 300 kg for Dreadnoughtus is highly
implausible and demonstrate that masses above 40 000 kg require high
body densities and expansions of soft tissue volume outside the
skeleton several times greater than found in living quadrupedal
mammals. Similar results from a small sample of other archosaurs
suggests that lower-end mass estimates derived from scaling equations
are most plausible for Dreadnoughtus, based on existing volumetric and
density data from extant animals. Although volumetric models appear to
more tightly constrain dinosaur body mass, there remains a clear need
to further support these models with more exhaustive data from living
animals. The relative and absolute discrepancies in mass predictions
between volumetric models and scaling equations also indicate a need
to systematically compare predictions across a wide size and taxonomic
range to better inform studies of dinosaur body size.