True's shrew mole (''Dymecodon pilirostris'') is a species of

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

in the family

Talpidae The family Talpidae () includes the moles (some of whom are called shrew moles and desmans) who are small insectivorous mammals of the order Eulipotyphla. Talpids are all digging animals to various degrees: moles are completely subterranean a ...

. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to Japan (

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island separ ...

Shikoku is the smallest of the four main islands of Japan. It is long and between wide. It has a population of 3.8 million (, 3.1%). It is south of Honshu and northeast of Kyushu. Shikoku's ancient names include ''Iyo-no-futana-shima'' (), '' ...

and

Kyushu is the third-largest island of Japan's five main islands and the most southerly of the four largest islands ( i.e. excluding Okinawa). In the past, it has been known as , and . The historical regional name referred to Kyushu and its surroun ...

) and is a common species above 1000 meters in grassland, shrubland and forest. Sometimes this species is called the lesser Japanese shrew mole and another species, '' Urotrichus talpoides'', is called the "greater Japanese shrew mole". It is the only species in the genus ''Dymecodon''. It has sometimes been considered belonging to the genus '' Urotrichus''.

Etymology

The genus name is the compound of δύο () "two", μήκος () "size", and όδούς () "tooth", so "two size teeth", because of the alternation in size of the teeth in the lower jaw.

Description

''D. pilirostris'' is a mole resembling the Japanese shrewmole, with a head-body length of about 6½ cm covered in thick, 5 mm long, darkbrown fur with a strong greenish metallic lustre, and a tail of about 3½ cm, covered with dark hair of about 7 mm. The palms and soles are covered in darkbrown scales. It differs somewhat from ''Urotrichus'' in overall size (smaller) and the relative size of its body parts (such as a relatively longer tail). Its

dentition 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-physiolo ...

however differs remarkably. The first

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, whe ...

in the upper jaw is low and broad, the broadest of all teeth in front of the true

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 ...

. The second is nearly as broad and comparable in shape. The third incisor and the canine are simple and rounded and about ¼ of the other incisors. The teeth in the lower jaw compare to those in the upper jaw, but the second incisor has an additional conic cusp at its back, there is no third incisor and the canine is minute.

References

Talpidae Mammals of Japan Endemic fauna of Japan Mammals described in 1886 Taxonomy articles created by Polbot {{talpidae-stub