Comments: | This group is complex, and although several important revisions have occurred (Emmons and Vucetich, 1998; Emmons et al., 2002; Laura and Patton, 2000; Patton and Emmons, 1985), additional revisions are needed. The family includes the most primitive fossil New World hystricognaths from the Early Oligocene of Patagonia. Reig (1986) noted that some living taxa in this family with brachyodont and pentalophodont molars (Mesomys and Lonchothrix) are of the type expected in the ancestral New World Hystricognathi. The family is also the most diverse of all Hystricognathi. Patterson and Wood (1982) included Chaetomys in the Echimyidae (subfamily Chaetomyinae) based on retention of deciduous premolars but see Martin (1994b) for a persuasive argument for returning this taxon to the Erethizontidae. Molecular data (Lara et al., 1996; Leite and Patton, 2002) suggest that the remaining living subfamilies (Dactylomyinae, Echimyidae, Eumysopinae) cannot be defined by monophyly, because of what appears to be a very rapid initial radiation (Leite and Patton, 2002). |