In studying the evolution of vertebrate locomotion, the focus for centuries has been on limb evolution. Despite significant evolutionary and developmental correlations among the limbs, vertebrae, and girdles, no biomechanical studies have ever examined the entire postcranial skeleton or explicitly considered the genetic and developmental processes that underly morphological variation, which are captured in phenotypic correlations. In this study, we will conduct experimental and geometric morphometric analyses of living and fossil cats, including the only large, crouching mammals, to study the evolution of locomotion, the mechanical consequences of size-related morphological evolution, and the evolution of correlations (modularity) in the postcranial musculoskeletal system.
Biomechanical analyses have rarely been unified, especially on the level of the whole skeleton, with the plethora of studies examining the genetic and developmental processes that underlie morphological variation, the raw material for natural selection. These genetic and developmental processes are, however, captured in studies of phenotypic modularity and thus can be studied in the same specimens as are used in biomechanical analyses.
Here, we provide the first comprehensive analysis of the intrinsic (genetic and developmental) and extrinsic (biomechanical) forces that shape the evolution of the postcranial skeleton from diminutive house cats to giant sabre-toothed cats, which display a unique postural solution to the problem of large body size. By bridging the disparate fields of functional biomechanics, palaeobiology, macroevolutionary trends, and developmental and phenotypic modularity, this study will provide a model of integrative evolutionary science and a foundation for future analyses on the evolution of form and function.