Phenotypic integration in the carnivoran backbone and the evolution of functional differentiation in metameric structures

Explaining the origin and evolution of a vertebral column with anatomically distinct regions that characterizes the tetrapod body plan provides understanding of how metameric structures become repeated and how they acquire the ability to perform different functions. However, despite many decades of inquiry, the advantages and costs of vertebral column regionalization in anatomically distinct blocks, their functional specialization, and how they channel new evolutionary outcomes are poorly understood. Here, we investigate morphological integration (and how this integration is structured [modularity]) between all the presacral vertebrae of mammalian carnivorans to provide a better understanding of how regionalization in metameric structures evolves. Our results demonstrate that the subunits of the presacral column are highly integrated. However, underlying to this general pattern, three sets of vertebrae are recognized as presacral modules –the cervical module, the antero-dorsal module, a...