Abstract:
Two ctenodactyloid rodents, Mergenomys orientalis, n. gen. and sp., and Butomys prima, n. gen. and sp., from the middle Eocene localities of the eastern Gobi Desert of Mongolia are described. Dental features that bear phylogenetic importance for ctenodactyloids are discussed. A cladistic analysis based primarily on dental features reveals the phylogenetic positions of the two new taxa. Mergenomys is closely related to the clade of the Ctenodactylidae, whereas Butomys is possibly related to Tsinlingomyinae. The analysis indicates that several traditional taxa of ctenodactyloids, such as Cocomyidae and Yuomyidae, are paraphyletic.