The history of South American octodontoid rodents and its contribution to evolutionary generalisations.

VERZI, D. H.; MORGAN, C.C.; OLIVARES, A. I.

Evolution of the Rodents. Advances in Phylogeny, Functional Morphology, and Development

Cambridge University Press

Año: 2015; p. 139 - 163

South American Octodontoidea is the most species-rich clade among both extinct and extant hystricomorph rodents. The evolutionary histories of its two major groups, Octodontidae and Echimyidae, are differentially linked to the main Cenozoic palaeoenviromental changes. According to a combined parsimony analysis of morphological and molecular data, they represent sister families, which were already separated in the late Oligocene, as well as the two major subclades comprised by each one. Whereas the octodontid subclades Octodontinae and Ctenomyinae show progressive stages of differentiation (modernisation) since the late Miocene, similar phases uncoupled from their respective origins are not recognisable in the echimyid subclades. The greater spread of modern octodontids in the morphospace of skull variation, and their greater relative disparity, independent of age and species richness, result from the abovementioned stages of differentiation and imply specialisation to open environments. Thus, the history of octodontoids suggests that the acquisition of evolutionary novelties is linked to the progressive emergence of new environments, and this link is manifested through different hierarchies, i.e. geographic, temporal and anagenetic (amount of change, irrespective of cladogenetic events). For these rodents, as well as for other terrestrial mammals, derived environments occur out of the tropics, thus highlighting the importance of extratropics as cradle of evolutionary novelties.