Descriptions of two new species of Rhynchomys Thomas (Rodentta: Muridae: Murinae) from Luzon Island, Philippines

Rhynchomys belongs to a unique assemblage of Philippine rodents that exhibit a combination of primitive features as well as unique morphological specializations. These nocturnal "shrew-rats," with highly specialized vermivorous and insectivorous food habits, are endemic to Luzon Island. Analyses of external, cranial, and dental features support the recognition of 4 species, 2 of which are described in this paper. All are restricted to high-elevation habitats, about 1,100 m and above, in montane and mossy forest on northern, western, and southeastern Luzon. Habitat vicariance and subsequent divergence in isolation is the probable mode of diversification in Rhynchomys as well as in other murid clades whose members are restricted to high-elevation habitats. The discovery of locally endemic species of Rhynchomys both confirms the existence of multiple centers of endemism on Luzon and underscores the need to establish and maintain additional protected areas on the island.