This project will study the nucleotide sequence data from one nuclear and three mitochondrial genes to test the monophyly of the Hystricognathi. Africa and South American rodents that share a common masticatory morphology expressed in characters of the zygomasseteric complex, the lower jaw and chewing musculature. This study, which will apply molecular analyses to the problem for the first time, bears directly on rodent evolution and relationships, on critical historical biogeographic issues such as the origin, and pattern, mechanism and timing of dispersal of the South American Paeogene mammals, and on paleontological issues such as the origin and homologies of characters preserved in the earliest known groups of fossil rodents from the Paleocene and Eocene.
