Patrones de evolución morfológica en Ctenomyinae (Rodentia, Octodontidae)

VERZI, D.H.

MASTOZOOLOGíA NEOTROPICAL

Año: 2002 vol. 9 p. 309 - 328

0327-9383

In the Cenozoic paleoclimatic history, arid climates and open habitats are clearly derived with respect to environmental conditions as those of the present-day tropical forests. This paleoclimatic context is closely related to the cranial-dental evolution of the Octodontoidea. The most ancient Octodontidae of the Subfamily Ctenomyinae are first recorded in the Late Miocene of southern South America. These early representatives (Chasichimys) are only slightly distinguishable from the generalized Echimyidae of the Subfamily Eumysopinae among which they were originally included. But the different responses of these groups to the Late Miocene climatic deterioration (adaptation of the Octodontidae, retraction to lower latitudes of the Echimyidae), make their recognition in the fossil record clear. The differentiation of the ctenomyines involved diverse adaptations to open habitats: (1) acquisition of molar euhypsodonty and associated changes (occlusal simplification, secondary acquisition of radial enamel on the molar leading edge), (2) acquisition of a crescent-shaped occlusal morphology adapted to an oblique mastication, and (3) fossorial specializations. At least in part of the group, these changes implied a phyletic evolutionary pattern (not necessarily gradual) without diversification. The anagenetic pattern in the adaptation to open habitats in ctenomyines supports the possibility of morphological divergence without implied differential cladogenesis.