New in PLoS ONE: Running Biomechanics and Endothermy in Dinosaurs

["Andrew A. Farke" <afarke@gmail.com>]

Pontzer H, Allen V, Hutchinson JR (2009) Biomechanics of Running 
Indicates Endothermy in Bipedal Dinosaurs. PLoS ONE 4(11): e7783. 
doi:10.1371/journal.pone.0007783

Freely available at:
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007783

Abstract
Background
One of the great unresolved controversies in paleobiology is whether 
extinct dinosaurs were endothermic, ectothermic, or some combination 
thereof, and when endothermy first evolved in the lineage leading to 
birds. Although it is well established that high, sustained growth rates 
and, presumably, high activity levels are ancestral for dinosaurs and 
pterosaurs (clade Ornithodira), other independent lines of evidence for 
high metabolic rates, locomotor costs, or endothermy are needed. For 
example, some studies have suggested that, because large dinosaurs may 
have been homeothermic due to their size alone and could have had heat 
loss problems, ectothermy would be a more plausible metabolic strategy 
for such animals.

Methodology/Principal Findings
Here we describe two new biomechanical approaches for reconstructing the 
metabolic rate of 14 extinct bipedal dinosauriforms during walking and 
running. These methods, well validated for extant animals, indicate that 
during walking and slow running the metabolic rate of at least the 
larger extinct dinosaurs exceeded the maximum aerobic capabilities of 
modern ectotherms, falling instead within the range of modern birds and 
mammals. Estimated metabolic rates for smaller dinosaurs are more 
ambiguous, but generally approach or exceed the ectotherm boundary.

Conclusions/Significance
Our results support the hypothesis that endothermy was widespread in at 
least larger non-avian dinosaurs. It was plausibly ancestral for all 
dinosauriforms (perhaps Ornithodira), but this is perhaps more strongly 
indicated by high growth rates than by locomotor costs. The polarity of 
the evolution of endothermy indicates that rapid growth, insulation, 
erect postures, and perhaps aerobic power predated advanced “avian” lung 
structure and high locomotor costs.