Shrewlike rat

Taxobox
name = Shrewlike rats
fossil_range = Recent


image_width = 250px
image_caption = "Rhynchomys soricoides" (lower animal)
regnum = Animalia
phylum = Chordata
classis = Mammalia
ordo = Rodentia
familia = Muridae
subfamilia = Murinae
genus = "Rhynchomys"
genus_authority = Thomas, 1895
subdivision_ranks = Species
subdivision = "Rhynchomys banahao" "Rhynchomys isarogensis" "Rhynchomys soricoides" "Rhynchomys tapulao"
range_

range_map_width = 200px
range_map_caption = Distribution of shrewlike rats on Luzon Island. Orange = "R. soricoides", red = "R. tapulao", blue = "R. banahao", and green = "R. isarogensis".

The shrewlike rats, genus "Rhynchomys", also known as the tweezer-beaked rats are a group of unusual Old World rats found only on the island of Luzon in the Philippines. They look a great deal like shrews and are an example of convergent evolution. Shrewlike rats evolved to be vermivores (worm-eaters) and insectivores feeding on soft-bodied invertebrates associated with leaf litter.

Characteristics

The snout and rostrum are very long. Eyes are small. Head and body is 18.8-21.5 cm with a tail 10.5-14.6 cm (Nowak, 1999). Only two molars are present; these are small and peg-like. Incisors are described as needle-like and mandibles as delicate (Nowak, 1999; Balete et al., 2007).

Distribution

Shrewlike rats are found at elevations of 1,100 to 2,460 meters (Nowak, 1999; Balete et al., 2007). They are restricted to moist, mossy highland regions with ample rainfall and large populations of earthworms. Populations appear to be very isolated, restricted to "sky islands" of Luzon. Specimens have been collected from Mount Bali-it and Mount Data of the Central Cordillera ("R. soricoides"), Mount Tapulao of the Zambalos Mountains ("R. tapulao"), Mount Banahao ("R. banahao"), and Mount Isarog ("R. isarogensis"; Balete et al., 2007).

Relationships

Musser and Heaney (1992) recognized "Rhynchomys" as an Old Endemic of the Philippines. They considered the genus distinct enough to give it its own group distinct from all other Old Endemics. Musser and Carleton (2005) classified it as part of the Chrotomys Division along with "Apomys", "Archboldomys", and "Chrotomys". Jansa et al. (2006) supported this relationship and determined that within this division, "Rhynchomys" is most closely related to the other Philippine shrew-rats in the genus "Archboldomys" and "Chrotomys".

pecies

From 1895 until 1981, "Rhynchomys" was only known from a few specimens taken from near the type locality of "R. soricoides". In 1981, this was expanded by one species with the discovery and description of "R. isarogensis". In April, 2007, Balete and colleagues described two additional species, "R. banahao" and "R. tapulao" from Mount Banahao and Mount Tapulao respectively.

* "Rhynchomys banahao" Balete, Rickart, Rosell-Ambal, Jansa, & Heaney, 2007
* Isarog Shrewlike Rat, "Rhynchomys isarogensis" Musser and Freeman, 1981
* Northern Luzon Shrewlike Rat - "Rhynchomys soricoides" Thomas, 1895
* "Rhynchomys tapulao" Balete, Rickart, Rosell-Ambal, Jansa, & Heaney, 2007

References

* Balete, D. S., E. A. Rickart, R. G. B. Rosell-Ambal, S. Jansa, and L. R. Heaney, 2007. Descriptions of two new species of Rhynchomys Thomas (Rodentia: Muridae: Murinae) from Luzon Island, Philippines. Journal of Mammalogy 88 (2): 287-301.
* Jansa, S., F. K. Barker, and L. R. Heaney. 2006. The pattern and timing of diversification of Philippene endemic rodents: evidence from mitochondrial and nuclear gene sequences. Systematic Biology, 55:73-88.
* Musser, G. G. and M. D. Carleton. 2005. Superfamily Muroidea. Pp. 894-1531 in "Mammal Species of the World a Taxonomic and Geographic Reference". D. E. Wilson and D. M. Reeder eds. Johns Hopkins University Press, Baltimore.
* Musser, G. G. and L. R. Heaney. 2006. Philippine rodents: Definitions of "Tarsomys" and "Limnomys" plus a preliminary assessment of phylogenetic patterns among native Philippine murines (Murinae, Muridae). Bulletin of the American Museum of Natural History, 211:1–138.
* Nowak, R.M. 1999. "Walker's Mammals of the World", Vol. 2. Johns Hopkins University Press, London.