Contrasting Phylogenetic and Diversity Patterns in Octodontoid Rodents and a New Definition of the Family Abrocomidae

Octodontoidea is the most species-rich cladeamong hystricomorph rodents. Based on a combined parsimonyanalysis of morphological and molecular data of extinctand extant species, we analyze the history of SouthAmerican octodontoids and propose ages of divergence olderthan interpreted so far. Early Abrocomidae are recognized forthe first time, and a new definition of the family is provided.Traditionally accepted fossil-based times of origin for thesouthern clades are reinterpreted as later stages of differentiationmarkedly uncoupled from the origin, differentiation implyingspecializations for open environments as shown in amorphospace of skull variation. Origin of crown groups is alsostrongly uncoupled from origin of clades as a consequence ofextinction of deep lineages. In the resulting diversity pattern ofmodern southern clades of octodontoids, the combination ofgreater disparity, less content of evolutionary history, and lowertaxonomic diversity, compared to their northern counterparts,appears at first counterintuitive.We propose that primarycomponents of diversity derived from evolutionary transformationor anagenesis, on the one hand, and from cladogenesisand extinction, on the other, should not be consideredassociated, or at least not necessarily. Certain patterns ofrelationships between these distinct components could bedriven by environmental dynamics. Like environments,octodontoid diversity would have been more stable in northernSouth America, whereas in the south, both strong adaptivechange and extinction would have been triggered by emergingderived environments.Fil: Verzi, Diego Hector. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados. Sección de Mastozoología; ArgentinaFil: Olivares, Adriana Itati. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados. Sección de Mastozoología; ArgentinaFil: Morgan, Cecilia Clara. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados. Sección de Mastozoología; ArgentinaFil: Alvarez, Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin