parent_taxon tylomyinae
___MASK88___ is the genus of the South American giant rats . It is named for Merle Kuns , a medical researcher who collected specimens of the woolly giant rat while studying rodent disease reservoirs in Bolivia . There are two species : The ___MASK80___ are a subfamily of the family ___MASK54___ . They consist of four tribes , 16 genera , and many species of New World rats and mice , predominantly found in North America . Among them are the well - known deer mice , white - footed mice , packrats , and grasshopper mice . The rodent subfamily ___MASK67___ is one of the most diverse groups of mammals . It includes New World rats and mice , with at least 376 species . Many authorities include the Neotominae and ___MASK82___ as part of a larger definition of ___MASK67___ . When those genera are included , the species count numbers at least 508 . Their distribution includes much of the New World , but the genera are predominantly South American , such as brucies . They invaded South America from Central America as part of the Great American Interchange near the end of the Miocene , about 5 million years ago . Sigmodontines proceeded to diversify explosively in the formerly isolated continent . They inhabit many of the same ecological niches that the ___MASK19___ occupy in the Old World . The ___MASK54___ are a family of rodents in the large and complex superfamily Muroidea . It includes true hamsters , voles , lemmings , and New World rats and mice . At almost 600 species , it is the second - largest family of mammals , and has members throughout the Americas , Asia , and Europe . The subfamily ___MASK82___ consists of several species of New World rats and mice including the vesper and climbing rats . They are not as well known as their relatives in the subfamilies Sigmodontinae and Neotominae . Many authorities place all three of these subfamilies in a single subfamily , Sigmodontinae . A vole is a small rodent ; a relative of the mouse , with a stouter body , a shorter , hairy tail , a slightly rounder head , smaller ears and eyes , and differently formed molars ( high - crowned and with angular cusps instead of low - crowned and with rounded cusps ). There are approximately 155 species of voles . They are sometimes known as meadow mice or field mice in North America and Australia . Vole species form the subfamily ___MASK61___ with the lemmings and the muskrats . ___MASK35___ is the genus of New World pygmy mice . Together with " ___MASK76___ ", it forms the tribe Baiomyini . It currently contains two extant species : The New World rats and mice are a group of related rodents found in North and South America . They are extremely diverse in appearance and ecology , ranging in from the tiny " ___MASK35___ " to the large " ___MASK88___ ". They represent one of the few examples of muroid rodents ( along with the voles ) in North America , and the only example of muroid rodents to have made it into South America . Rats are various medium - sized , long - tailed rodents of the superfamily ___MASK69___ . " True rats " are members of the genus " Rattus ", the most important of which to humans are the black ___MASK6___ , " Rattus rattus ", and the brown ___MASK6___ , " Rattus norvegicus ". Many members of other rodent genera and families are also referred to as rats , and share many characteristics with true rats . Rodents ( from Latin " rodere ", " to gnaw ") are mammals of the order ___MASK86___ , 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 rodents ; they are found in vast numbers on all continents except Antarctica . They are the most diversified mammalian order and live in a variety of terrestrial habitats , including human - made environments . The Old World rats and mice , part of the subfamily ___MASK19___ in the family ___MASK68___ , comprise at least 519 species . Members of this subfamily are called murines . This subfamily is larger than all ___MASK56___ families except the ___MASK54___ and ___MASK68___ , and is larger than all ___MASK56___ orders except the bats and the remainder of the rodents .