A unicuspid is a tooth that has only one cusp.

In shrews

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 different fa ...

s are distinguished by the number of unicuspids. All shrews have (in one half of each jaw) one large incisor followed by a variable number of unicuspids, followed by a complex

premolar The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...

, followed by three molars. All shrews except for those of the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Myosorex ''Myosorex'' is a mammal genus in the Soricidae (shrew) family. The genus, collectively referred to as the mouse shrews, contains these species: * Babault's mouse shrew, ''M. babaulti'' * Montane mouse shrew, ''M. blarina'' * Bururi forest shr ...

'' have one lower unicuspid; ''Myosorex'' has two. The

genera 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 nomenclat ...

'' Blarina'', '' Blarinella'', and '' Sorex'' have five upper unicuspids. The genera ''Myosorex'', '' Feroculus'', ''

Scutisorex ''Scutisorex'' is a genus of African shrews, mammals of the family Soricidae. Members of the genus are the only known mammal species whose vertebrae interlock, a feature which, along with the general enlargement and strengthening of the backbone ...

'', '' Suncus'', ''

Sylvisorex The forest shrews are the members of the genus ''Sylvisorex''. They are mammals in the family Soricidae and are found only in Africa. The genus name comes from the Latin world "silva" which means "forest" and "sorex", which means "shrew-mouse". ...

'', ''

Ruwenzorisorex The Ruwenzori shrew (''Ruwenzorisorex suncoides'') is a species of mammal in the family Soricidae. It is the only species within the genus ''Ruwenzorisorex''. It is found in Burundi, Democratic Republic of the Congo, Rwanda, and Uganda. It is s ...

'', ''

Cryptotis The genus ''Cryptotis'' is a group of relatively small shrews with short ears, which are usually not visible, and short tails, commonly called small-eared shrews. They have 30 teeth and are members of the red-toothed shrew subfamily. Since 1992, ...

'', '' Neomys'', ''

Soriculus ''Soriculus'' is a genus of shrew native to Asia. The Himalayan shrew ''(Soriculus nigrescens)'' is the only extant member of the genus, though other species were once included here and there are also several fossil species included here. Taxonom ...

'', and ''

Episoriculus ''Episoriculus'' is a genus of shrew in the red-toothed shrew subfamily. Its common is brown-toothed shrew. It has been described as a subgenus to ''Soriculus'' in the past. The genus occurs at a number of locations in Asia, including Nepal and C ...

'' have four upper unicuspids. The genera '' Congosorex'', ''

Surdisorex ''Surdisorex'' is a genus of mammals in the family Soricidae. ''Surdisorex'' is one of three genera of African shrews, which, in turn, are one of three living subfamilies of shrews. Species in the genus ''Surdisorex'' are called African mole s ...

'', '' Solisorex'', ''

Paracrocidura ''Paracrocidura'' is a genus of shrews. They are mammals in the family Soricidae. The vernacular name large-headed shrews is sometimes collectively applied to the genus, but has also been applied to the species '' Crocidura grandiceps''. The g ...

'', '' Crocidura'', ''

Chimarrogale The Asiatic water shrews are the members of the genus ''Chimarrogale''. They are mammals in the subfamily Soricinae of the family Soricidae. They are aquatic, with some species inhabiting streams. The genus contains the following species: * Mala ...

'', '' Chodsigoa'', ''

Megasorex The Mexican shrew (''Megasorex gigas'') is a species of mammal from the subfamily Soricinae in the family Soricidae. It is monotypic within the genus ''Megasorex'' and is endemic to Mexico Mexico (Spanish: México), officially the United ...

'', ''

Nectogale The elegant water shrew (''Nectogale elegans'') is a species of mammal in the subfamily Soricinae of the family Soricidae. It is the only species within the genus ''Nectogale''. It lives in Sikkim and China China, officially the People ...

'', and ''

Notiosorex ''Notiosorex'' is a genus of Shrew (animal), shrew from the subfamily Soricinae. History ''Notiosorex'' shrews have a fossil history that extends to the Miocene (i.e., mid-Hemphillian). The geographic distribution of the genus has always been in ...

'' have three upper unicuspids. The genera ''

Diplomesodon ''Diplomesodon'' is a genus of shrew that contains a single extant species, the piebald shrew ''(Diplomesodon pulchellum)''. Taxonomy An extinct species named '' Diplomesodon fossorius'' is known from the Early Pleistocene of South Africa, ver ...

'' and ''

Anourosorex Asian mole shrews (''Anourosorex'') are a genus of shrews that resemble moles, from China, Taiwan, India, and Indochina. They are the only known genus of the Anourosoricini tribe of red-toothed shrews. The four known species are:Teeth {{Dentistry-stub