Holarctic radiation of Neogene muroid rodents and the origin of South American cricetids

A review of the fossil record suggests that Calomys (Bensonomys) may be derived from Megacricetodon from the Miocene of Eurasia. If this is true, South American sigmodontine cricetids could be less closely related to North American peromyscines than to some Old World muroids. An origin of Calomys (Bensonomys) from megacricetodontine ancestors is consistent with some neonto-logical approaches based on host–parasite distributions and penile morphology.