The shrewlike rats,

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Rhynchomys'', also known as the tweezer-beaked rats are a group of unusual Old World rats found only on the island of

Luzon Luzon ( , ) is the largest and most populous List of islands in the Philippines, island in the Philippines. Located in the northern portion of the List of islands of the Philippines, Philippine archipelago, it is the economic and political ce ...

in the

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

. They look a great deal like

shrew Shrews ( family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to dif ...

s and are an example of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

. Shrewlike rats evolved to be vermivores and

insectivore file:Common brown robberfly with prey.jpg, A Asilidae, robber fly eating a hoverfly An insectivore is a carnivore, carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the Entomophagy ...

s feeding on soft-bodied

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s associated with

leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall, or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that has fallen to the ground. This detritus or dead organic material and its constituen ...

Characteristics

The snout and

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...

are very long. Eyes are small. Head and body is 18.8–21.5 cm with a tail 10.5–14.6 cm. Only two molars are present on each side of the upper and lower jaws; these are small and peg-like.

Incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

s are described as needle-like and

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

s as delicate. Their characteristic method of locomotion has given rise to the epithet "hopping rats," describing their method of pouncing on an earthworm prey before it can slide back into its hole.

Distribution

Shrewlike rats are found at elevations of 1,100 to 2,460 meters. They are restricted to moist, mossy highland regions with ample rainfall and large populations of

earthworm An earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. In classical systems, they we ...

s. Populations appear to be very isolated, restricted to "

sky island Sky islands are isolated mountains surrounded by radically different lowland environments. The term originally referred to those found on the Mexican Plateau and has extended to similarly isolated high-elevation forests. The isolation has s ...

s" of Luzon. Specimens have been collected from Mt. Bali-it and Mt. Data of the Central Cordillera (''R. soricoides''),

Mt. Tapulao Mount Tapulao (also known as High Peak) is the highest mountain in the Zambales Mountains, Zambales Mountain Range and in the Provinces of the Philippines, province of Zambales in the Philippines. The peak, which rises to an elevation of above s ...

of the

Zambales Mountains The Zambales Mountains is a mountain range in western Luzon. The mountains spread along a north-south axis, separating Luzon's central plain from the South China Sea. The range extends into five Provinces of the Philippines, provinces: Zambales, ...

(''R. tapulao''),

Mount Banahao Mount is often used as part of the name of specific mountains, e.g. Mount Everest. Mount or Mounts may also refer to: Places * Mount, Cornwall, a village in Warleggan parish, England * Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, C ...

(''R. banahao''),

Mount Isarog Isarog is an List of active volcanoes in the Philippines, active stratovolcano located in the province of Camarines Sur, Camarines Sur, Philippines, on the island of Luzon. The mountain has active Fumarole, fumaroles and Hot spring, hot springs. It ...

(''R. isarogensis''), Mt. Labo of the

Bicol Peninsula The Bicol Region, designated as Region V, is an administrative region of the Philippines. It comprises six provinces, four on the Bicol Peninsula (the southeastern end of Luzon): Albay, Camarines Norte, Camarines Sur, and Sorsogon, and two ...

(''R. labo'') and Mt. Mingan of the

Sierra Madre Sierra Madre (Spanish, 'mother mountain range') may refer to: Places and mountains Mexico *Sierra Madre Occidental, a mountain range in northwestern Mexico and southern Arizona *Sierra Madre Oriental, a mountain range in northeastern Mexico *S ...

(''R. mingan'').

Relationships

''Rhynchomys'' is an old endemic of the Philippines. The genus is distinct enough to give it its own group distinct from all other old endemics. It was classified as part of the ''Chrotomys'' division along with ''

Apomys ''Apomys'', commonly known as earthworm mice, is a genus of rodent endemic to the Philippines. Mice belonging to this genus are generally called Philippine forest mice and can be found on most islands of the Philippines The Philippines, ...

'', ''

Archboldomys ''Archboldomys'', the shrew-mice, are a genus of rodents in the family Muridae. They are carnivores that feed on invertebrates much like shrews do. An apparently smaller relatives of the true shrew-rats ''Chrotomys'' and '' Rhynchomys'', ''Archbo ...

'', and ''

Chrotomys The genus ''Chrotomys'' contain a unique group of rodents found only in the Philippines, specifically the islands of Luzon, Mindoro, and Sibuyan. Instead of being predominantly herbivorous or omnivorous like other murines, these rats feed pre ...

''. Within this division, ''Rhynchomys'' is most closely related to the other Philippine shrew-rats in the genera ''Archboldomys'' and ''Chrotomys''.

Species

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 2007, two species, ''R. banahao'' and ''R. tapulao'', were described from Mt. Banahao and Mt. Tapulao, respectively. In 2019, two additional species were described, ''R. labo'' and ''R. mingan'' from Mt. Labo and Mt. Mingan, respectively. * Banahao shrew-rat (''Rhynchomys banahao'') Balete ''et al.'', 2007 * Isarog shrew-rat, (''Rhynchomys isarogensis'') Musser and Freeman, 1981 *

Labo shrew-rat The Labo shrew rat (''Rhynchomys labo'') is a species of shrewlike rat in the subfamily Murinae. It was discovered at elevations above 1250 m on Mt. Labo of the Bicol Peninsula of Luzon in the Philippines The Philippines, officially the ...

(''Rhynchomys labo'') Rickart ''et al.'', 2019 * Mingan shrew-rat (''Rhynchomys mingan'') Rickart ''et al.'', 2019 * Mount Data shrew-rat (''Rhynchomys soricoides'') Thomas, 1895 * Tapulao shrew-rat (''Rhynchomys tapulao'') Balete ''et al.'', 2007

References

{{Taxonbar, from=Q1189626 Rats of Asia Rhynchomys Endemic fauna of the Philippines Fauna of Luzon Rodents of the Philippines Taxa named by Oldfield Thomas