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

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

in the family

Talpidae The family (biology), family Talpidae () includes the true Mole (animal), moles (as well as the shrew moles and desmans) who are small insectivore, insectivorous mammals of the order (biology), order Eulipotyphla. Talpids are all fossorial, diggi ...

. It is

endemic Endemism is the state of a species being found only 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 foun ...

to Japan (

Honshu , historically known as , is the largest of the four main islands of Japan. It lies between the Pacific Ocean (east) and the Sea of Japan (west). It is the list of islands by area, seventh-largest island in the world, and the list of islands by ...

Shikoku is the smallest of the List of islands of Japan#Main islands, four main islands of Japan. It is long and between at its widest. It has a population of 3.8 million, the least populated of Japan's four main islands. It is south of Honshu ...

and

Kyushu is the third-largest island of Japan's Japanese archipelago, four main islands and the most southerly of the four largest islands (i.e. excluding Okinawa Island, Okinawa and the other Ryukyu Islands, Ryukyu (''Nansei'') Ryukyu Islands, Islands ...

) 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 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 ...

''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 shrew mole, 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-physiology ...

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, wher ...

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 tooth, teeth at the back of the mouth. They are more developed in mammal, mammals. They are used primarily to comminution, grind food during mastication, chewing. The name ''molar'' derives from Latin, '' ...

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