A saltation model of karyotypic evolution in the Octodontoidea (Mammalia, Rodentia)

Abstract

The suborder Caviomorpha was erected to group all South American and Antillean hystricognath rodents, although hystricognathy also is observed in some African counterparts (Woods, 1982). The abrupt appearance of miocenic caviomorph fossils represents an unsolved phylogenetic problem with two competing hypotheses attempting to explain the source area of the Caviomorpha. One hypothesis proposes a mid-Cenozoic immigration of rodents to South America from the early Eocene Franimorphs of North America, whereas the alternative hypothesis proposes an African origin (Wyss et al., 1993). The fossil fauna in the central Chilean Andes indicate a boundary between 31.5–37.5 myr for the group’s occurrence in South America, and favour the African origin over the South-American radiation. (Wyss et al., 1993). A recent 12S rRNA gene phylogeny of selected genera of hystricognaths also supports the monophyletic origin of the Octodontoidea, containing the families Capromyidae, Ctenomyidae, Echimyidae, Myocastoridae and Octodontidae (Nedbal et al., 1994).