Cricetidae
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The Cricetidae are a family of
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 Mandible, lower jaws. About 40% of all mammal specie ...
s in the large and complex superfamily Muroidea. It includes true hamsters,
vole Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of lo ...
s, lemmings, muskrats, and New World rats and mice. At over 870 species, it is either the largest or second-largest family 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 ...
s, and has members throughout the Americas, Europe and Asia.


Characteristics

The cricetids are small mammals, ranging from just in length and in weight in the New World pygmy mouse up to and in the muskrat. The length of their tails varies greatly in relation to their bodies, and they may be either furred or sparsely haired. The fur of most species is brownish in colour, often with a white underbelly, but many other patterns exist, especially in the cricetine and arvicoline subfamilies. Like the Old World mice, cricetids are adapted to a wide range of habitats, from the high
Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...
to tropical rainforests and hot
desert A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the la ...
s. Some are arboreal, with long balancing tails and other adaptations for climbing, while others are semiaquatic, with webbed feet and small external ears. Yet others are burrowing animals, or ground-dwellers.Eisenberg ''et al.'' (1984) Their diets are similarly variable, with herbivorous, omnivorous, and insectivorous species all being known. They all have large, gnawing, incisors separated from grinding molar teeth by a gap, or diastema. Molar teeth may be buno-lophodont like in cricetines or lophodont like in arvicolines or some New World mice. Although a few exceptions occur, the dental formula for the great majority of cricetids is: Cricetids' populations can increase rapidly in times of plenty, due to a combination of short gestation periods between 15 and 50 days, and large litter sizes relative to many other mammals. The young are typically born blind, hairless, and helpless.


Evolution and systematics

The cricetids first evolved in the Old World during the Early
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
. They soon adapted to a wide range of habitats, and spread throughout the world. The voles and lemmings arose later, during the Pliocene, and rapidly diversified during the Pleistocene. The circumscription of Cricetidae has gone through several permutations. Some members of the family as currently defined have been placed in the family Muridae. Some muroids have historically been placed in Cricetidae, such as mouse-like hamsters (subfamily Calomyscinae, family Calomyscidae), gerbils (subfamily Gerbillinae, family Muridae), the crested rat (subfamily Lophiomyinae, family Muridae), zokors (subfamily Myospalacinae, family Spalacidae), the white-tailed rat (subfamily Mystromyinae, family Nesomyidae), and spiny dormice (subfamily Platacanthomyinae, family Platacanthomyidae). Multigene DNA sequence studies have shown the subfamilies listed below to form a
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
group (that is, they share a common ancestor more recently than with any other group), and other groups now considered muroids should not be included in the Cricetidae.Michaux ''et al.'' (2001), Jansa & Weksler (2004), Norris ''et al.'' (2004), Steppan ''et al.'' (2004) The cricetids thus currently include one fossil and five extant subfamilies, with about 112 living genera and 580
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
: * Arvicolinae
vole Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of lo ...
s, lemmings, muskrat * Cricetinaehamsters * † Democricetodontinae ( fossil) * Neotominae — North American rats and mice, including deer mice, pack rats, and grasshopper mice * Sigmodontinae — New World rats and mice, predominantly South American, such as brucies * Tylomyinae — New World climbing rats and relatives * †'' Copemys'' ( fossil) * †'' Eumys'' ( fossil) * †'' Wilsoneumys'' ( fossil)


References

* Eisenberg, J.F.; Feaver, J. & Krebs, C.J. (1984): Cricetidae. In: : ''The Encyclopedia of Mammals'': 640–655, 672–673. Facts on File, New York. * * * * Savage, R.J.G. & Long, M.R. (1986): ''Mammal Evolution: an illustrated guide''. Facts on File, New York. * {{Authority control Rodent families Extant Miocene first appearances Taxa named by Gotthelf Fischer von Waldheim