Relationship of South American cricetines to rodents of North America and the Old World

ABSTRACT

The occurrences of sigmodontine rodents in the Hemphillian Land Mammal Age of Arizona and northern Mexico have been offered as evidence for a North American origin of South American cricetines from a common ancestor of peromyscines, Copemys. The discovery of neotomines and peromyscines associated with sigmodontines in the Hemphillian of central Mexico, combined with the previously reported evidence of ectoparasite distributions and the distribution of nematode endoparasites belonging to the genus Parastrongylus suggest a dual origin of New World cricetines. These data are consistent with the hypothesis that the North and South American cricetines did not have a common New World ancestor. The Copemys–peromyscine lineage may have had an origin from eumyines independent of the Old World cricetodontines, or evolved directly from the Old World cricetodontines and migrated to the New World.