Data from: Energetic benefits and adaptations in mammalian limbs: scale effects and selective pressures

Differences in limb size and shape are fundamental to mammalian
morphological diversity; however, their relevance to locomotor costs has
long been subject to debate. In particular, it remains unknown if scale
effects in whole limb morphology could partially underlie decreasing
mass-specific locomotor costs with increasing limb length. Whole fore- and
hindlimb inertial properties reflecting limb size and shape – moment of
inertia (MOI), mass, mass distribution, and natural frequency – were
regressed against limb length for 44 species of quadrupedal mammals. Limb
mass, MOI, and center of mass position are negatively allometric, having
strong potential for lowering mass-specific locomotor costs in large
terrestrial mammals. Negative allometry of limb MOI results in a 40%
reduction in MOI relative to isometry for our largest sampled taxa.
However, fitting regression residuals to adaptive diversification models
reveals that co-diversification of limb mass, limb length, and body mass
likely results from selection for differing locomotor modes of running,
climbing, digging, and swimming. The observed allometric scaling does not
result from selection for energetically beneficial whole limb morphology
with increasing size. Instead, our data suggest that it is a consequence
of differing morphological adaptations and body size distributions among
quadrupedal mammals, highlighting the role of differing limb functions in
mammalian evolution.