The murine rodent, Sommeromys macrorhinos, new genus and species, is described from a single specimen collected at 2400 m near the summit of Gunung Tokala in central Sulawesi. The species is insectivorous and a member of the tropical upper montane rain forest fauna of the island. With its small body, elongate rostrum, long and slender hind feet, very long tail, and brownish gray fur, S. macrorhinos superficially resembles the long-tailed and small-bodied shrew rat, Tateomys macrocercus, another Sulawesian upper montane forest endemic. Sommeromys macrorhinos, however, possesses a combination of derived external, cranial, and dental traits, along with a unique rostral shape, that dissassociates it from any relationship with not only T. macrocercus and its close allies T. rhinogradoides and Melasmothrix naso, but with also the large-bodied shrew rats of Sulawesi (Echiothrix) and those indigenous to the Philippines (Archboldomys, Rhyncomys, Chrotomys, and Celaenomys) and New Guinea (Neohydromys, Pseudohydromys, Microhydromys, and Mayermys). The rostral configuration of Sommeromys is unlike the architecture found in any other of the more than 1300 species in the entire Muridae. The new species has a derived cephalic arterial circulation, a pattern otherwise found only in Crunomys celebensis among Sulawesian murines. That species, although usually regarded as a shrew rat, also does not possess any of the external and cranial specializations defining the species of Melasmothrix, Tateomys, and Echiothrix. Crunomys and Sommeromys share a similar conformation of the zygomatic plate that is not found in any other Sulawesian murine, but this is a shared primitive feature. Whether the shared cephalic arterial circulation indicates a closer relationship between Crunomys celebensis and Sommeromys macrorhinos than to any other native Sulawesi species, despite the striking contrast between the two in body form and a combination of cranial and dental traits, or independent derivation in each species will have to be determined by phylogenetic analysis of all the Sulawesi species as well as pertinent samples from the Sunda Shelf and Indochina.
A new species of sucking louse, Hoplopleura sommeri (Insecta, Anoplura, Hoplopleuridae), is also described from the new murine. A brief discussion on related species of Hoplopleura is included with emphasis on those species parasitizing hosts in the subfamily Murinae of family Muridae.