''Paucidentomys'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are roden ...

s of a type commonly known as shrew-rats which was discovered in 2012 in a remote rainforest on the

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

n island, Sulawesi. The genus is

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

, consisting of the species ''Paucidentomys vermidax'', or the edented Sulawesi rat. The

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

name may also be translated to its other common name "few-toothed worm-eating rat", referring to the fact that they have only two teeth and may live exclusively on a diet of

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. ...

Description

''Paucidentomys vermidax'' is larger than ''

Melasmothrix naso The Sulawesian shrew rat (''Melasmothrix naso'') is a species of rodent in the family Muridae. It is the only species in the genus ''Melasmothrix''. It is found only in central Sulawesi Sulawesi (), also known as Celebes (), is an island i ...

'', ''

Sommeromys macrorhinos Sommer's Sulawesi rat (''Sommeromys macrorhinos'') is a species of rodent in the family Muridae from Sulawesi. It is the only species in the monotypic genus ''Sommeromys'' and was described by Musser & Durden in 2002. Distribution ''S. macrorhi ...

'' and ''

Tateomys macrocercus The long-tailed shrew rat (''Tateomys macrocercus'') is a species of rodent in the family Muridae. It is found only in Central Sulawesi, Indonesia, where it is known only from Mount Nokilalaki in Sigi Regency Sigi Regency is a regency of Central ...

'', similar in size to ''

Tateomys rhinogradoides Tate's shrew rat (''Tateomys rhinogradoides'') is a species of rodent in the family Muridae. It is found only in central Sulawesi, Indonesia, where it has been recorded on Mount Latimodjong (Mount Rantemario), Mount Tokala, and Mount Nokilalaki. ...

'', smaller than '' Rhynchomys soricoides'' and substantially smaller than species of '' Echiothrix''. The face is more elongate than that of any other Sulawesi shrew-rat, but similar in this regard to '' Rhynchomys''. It has a very long rostrum (relative to other Sulawesi shrew-rats), small eyes, large ears, a soft

pelage Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an insulating blanket t ...

and a long, thick, hairy and dorsoventrally bicoloured tail.

Unique dentition

''Paucidentomys vermidax'' is the only known rodent with no

molars The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

, which is an adaptation to its diet which may be exclusively

s (it appears to be a specialist vermivore based on the stomach contents of one individual). Moreover, rather than gnawing

incisors 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, wh ...

, this animal has bicuspid upper incisors, which is also unique among the more than 2,200 species of rodents. The upper incisors are short with an anterior cusp and slightly inferior posterior cusp; these cusps are connected by a sharp, concave cutting edge at the

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction * Lateral cricoarytenoid muscle * Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral co ...

margin of the tooth. The pterygoid plate is absent. The

dentary In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

is long and delicate, lacking significant muscle attachment points. The lower incisors are unicuspid, procumbent, sharp and delicate. Its

dental formula Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolog ...

is .

Distribution

''Paucidentomys vermidax'' is known from Mount Gandangdewata and

Mount Latimojong Latimojong (Indonesian: Gunung Latimojong), also known by its peak name Rantemario, is a mountain located in the province of South Sulawesi, Sulawesi, Indonesia. At , it is the highest mountain on the island, although some sources state Mount Ra ...

in Sulawesi, Indonesia.

Etymology

The generic name combines the Latin ''paucus'' (few) with ''dentis'' (tooth) and the Greek ''mys'' (mouse) in reference to the lack of molars. The epithet is a hybrid of ''vermi'' (worm) and ''edax'' (devourer), in reference to the animal's diet.

References

{{Taxonbar, from1=Q18643215, from2=Q148559 Muridae Endemic fauna of Indonesia Rodents of Sulawesi Mammals described in 2012 Old World rats and mice