Rodent
Encyclopedia
Rodentia is an order
of mammal
s also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing.
Forty percent of mammal species are rodents, and they are found in vast numbers on all continents other than Antarctica. Common rodents include mice
, rat
s, squirrel
s, porcupine
s, beaver
s, guinea pig
s, and hamster
s. Rodents have sharp incisors that they use to gnaw wood, break into food, and bite predators. Most eat seeds or plants, though some have more varied diets. Some species have historically been pests, eating seeds stored by people and spreading disease.
—although not necessarily in terms of number of organisms (population) or biomass
—rodents make up the largest order of mammals. There are about 2,277 species
of rodents (Wilson and Reeder, 2005), with over 40 percent of mammalian species belonging to the order. Their success is probably due to their small size, short breeding cycle, and ability to gnaw and eat a wide variety of foods. (Lambert, 2000)
Rodents are found in vast numbers on all continents except Antarctica, most islands, and in all habitats except oceans. They are the only non-volant, non-marine placental order—and in particular are the only placental order besides bat
s (Chiroptera) and Pinniped
s—to have reached Australia
without human introduction.
All rodents share the characteristic that their dentition is highly specialised for gnawing. It is this specialisation which gives rodents their name from the Latin, rodere, to gnaw and dens, dentis, tooth. All rodents have a single pair of upper and a single pair of lower incisors, followed by a gap (diastema), and then one or more molars or premolars. Rodent incisors grow continuously and must be kept worn down by gnawing. Their anterior and lateral
surfaces are covered with enamel
, but the posterior surface is exposed dentine. During gnawing, the incisors grind against each other, wearing away the softer dentine leaving the enamel edge as the blade of a chisel. This ‘self-sharpening’ system is very effective and is one of the keys to the enormous success of rodents. Rodents lack canines
, and have a space (diastema
) between their incisor
s and premolar
s. Rodents use their teeth for cutting wood, biting through the skin of fruit, or for defense. Nearly all rodents feed on plants, seeds in particular, but there are a few exceptions which eat insects (grasshopper mouse, Onychomys leucogaster) or fish (beavers, Castor spp.). Some squirrels are known to eat passerine
bird
s like cardinal
s and blue jay
s.
Many rodents are small; the tiny African pygmy mouse
, Mus minutoides, can be as little as 6 cm (2.4 in) in length and 7 g (0.246917734735784 oz) in weight at maturity, and the Baluchistan Pygmy Jerboa
, Salpingotulus michaelis, is of roughly similar or slightly smaller dimensions. On the other hand, the capybara
, Hydrochoerus hydrochaeris, usually weighs up to 65 kg although one individual was reported as weighing 91 kg, and the largest known rodent, the extinct Josephoartigasia monesi
, is estimated to have weighed about 1000 kg (2,204.6 lb), and possibly up to 1534 kg (3,381.9 lb) or 2586 kg (5,701.2 lb).
, and as disease vectors. Humans use rodents as a source of fur
, as pets, as model organism
s in animal testing, for food, and even for detecting landmines
. Due to the wide diversity of their characteristics, some of which are considered uncommon or unique amongst mammals, rodents are used widely in research. For example, the Naked mole rat
, Heterocephalus glaber, is the only know mammal that is poikilothermic and also does not produce the neurotransmitter substance P
; it is therefore used in studies on thermoregulation
and pain
.
Members of non-rodent orders such as Chiroptera (bats), Scandentia (treeshrew
s), Soricomorpha
(shrew
s and mole
s), Lagomorpha
(hare
s, rabbit
s and pika
s) and mustelid carnivore
s such as weasel
s and mink
are sometimes confused with rodents.
The fossil
record of rodent-like mammals begins shortly after the extinction of the non-avian dinosaur
s 65 million years ago, as early as the Paleocene
. Some molecular clock
data, however, suggest that modern rodents (members of the order Rodentia) already appeared in the late Cretaceous
, although other molecular divergence estimations are in agreement with the fossil record. By the end of the Eocene
epoch, relatives of beavers, dormice
, squirrels, and other groups appeared in the fossil record. They originated in Laurasia
, the supercontinent composed of today's North America
, Europe
, and Asia. Some species colonized Africa
, giving rise to the earliest hystricognaths
. From Africa hystricognaths rafted
to South America
, an isolated continent
during the Oligocene
and Miocene
epochs. By the Miocene
, Africa collided with Asia, allowing rodents such as porcupine
s to spread into Eurasia
. During the Pliocene
, rodent fossils appeared in Australia. Although marsupial
s are the most prominent mammals in Australia, rodents now make up almost 25% of the continent's mammal species. Meanwhile, the Americas became joined by the Isthmus of Panama
and some rodents participated in the resulting Great American Interchange
; sigmodontines
surged southward and caviomorphs
headed north.
Some prehistoric rodents
s Glires
(along with lagomorphs
), Euarchontoglires
(along with lagomorphs
, primate
s, treeshrew
s, and colugo
s), and Boreoeutheria
(along with most other placental
mammal
s). The order Rodentia may be divided into suborders, infraorders, superfamilies
and families
.
Classification scheme:
ORDER RODENTIA (from Latin, rodere, to gnaw)
uses the shape of the lower jaw
(sciurognath
or hystricognath
) as the primary character. This is the most commonly used approach for dividing the order
into suborders. Many older references emphasize the zygomasseteric system
(suborders Protrogomorpha, Sciuromorpha
, Hystricomorpha
, and Myomorpha
).
Several molecular phylogenetic
studies have used gene
sequences to determine the relationships among rodents, but these studies are yet to produce a single consistent and well-supported taxonomy
. Some clade
s have been consistently produced such as:
The positions of the Castoridae
, Geomyoidea
, Anomaluridae, and Pedetidae
are still being debated.
s should be reclassified as a separate order (similar to Lagomorpha
), based on an analysis of the amino acid
sequences of guinea pig
s. This hypothesis was refined in a 1992 paper, which asserted the possibility that caviomorphs may have diverged from myomorph
s prior to later divergences of Myomorpha; this would mean caviomorphs, or possibly hystricomorph
s, would be moved out of the rodent classification into a separate order. A minority scientific opinion briefly emerged arguing that guinea pig
s, degu
s, and other caviomorphs are not rodents, while several papers were put forward in support of rodent monophyly
. Subsequent studies published since 2002, using wider taxon
and gene
samples, have restored consensus among mammalian biologists that the order Rodentia is monophyletic.
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing.
Forty percent of mammal species are rodents, and they are found in vast numbers on all continents other than Antarctica. Common rodents include mice
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
, rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s, squirrel
Squirrel
Squirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots , flying squirrels, and prairie dogs. Squirrels are indigenous to the Americas, Eurasia, and Africa and have been introduced to Australia...
s, porcupine
Porcupine
Porcupines are rodents with a coat of sharp spines, or quills, that defend or camouflage them from predators. They are indigenous to the Americas, southern Asia, and Africa. Porcupines are the third largest of the rodents, behind the capybara and the beaver. Most porcupines are about long, with...
s, beaver
Beaver
The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...
s, guinea pig
Guinea pig
The guinea pig , also called the cavy, is a species of rodent belonging to the family Caviidae and the genus Cavia. Despite their common name, these animals are not in the pig family, nor are they from Guinea...
s, and hamster
Hamster
Hamsters are rodents belonging to the subfamily Cricetinae. The subfamily contains about 25 species, classified in six or seven genera....
s. Rodents have sharp incisors that they use to gnaw wood, break into food, and bite predators. Most eat seeds or plants, though some have more varied diets. Some species have historically been pests, eating seeds stored by people and spreading disease.
Size and range of order
In terms of number of speciesSpecies
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
—although not necessarily in terms of number of organisms (population) or biomass
Biomass (ecology)
Biomass, in ecology, is the mass of living biological organisms in a given area or ecosystem at a given time. Biomass can refer to species biomass, which is the mass of one or more species, or to community biomass, which is the mass of all species in the community. It can include microorganisms,...
—rodents make up the largest order of mammals. There are about 2,277 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of rodents (Wilson and Reeder, 2005), with over 40 percent of mammalian species belonging to the order. Their success is probably due to their small size, short breeding cycle, and ability to gnaw and eat a wide variety of foods. (Lambert, 2000)
Rodents are found in vast numbers on all continents except Antarctica, most islands, and in all habitats except oceans. They are the only non-volant, non-marine placental order—and in particular are the only placental order besides bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s (Chiroptera) and Pinniped
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
s—to have reached Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
without human introduction.
Dentition
Lateral
Lateral may refer to:*Lateral , an anatomical direction*Lateral canal, a canal built beside another stream*Lateral consonant, an ℓ-like consonant in which air flows along the sides of the tongue...
surfaces are covered with enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
, but the posterior surface is exposed dentine. During gnawing, the incisors grind against each other, wearing away the softer dentine leaving the enamel edge as the blade of a chisel. This ‘self-sharpening’ system is very effective and is one of the keys to the enormous success of rodents. Rodents lack canines
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
, and have a space (diastema
Diastema (dentistry)
Diastema is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars.-In humans:...
) between their incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s and premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
s. Rodents use their teeth for cutting wood, biting through the skin of fruit, or for defense. Nearly all rodents feed on plants, seeds in particular, but there are a few exceptions which eat insects (grasshopper mouse, Onychomys leucogaster) or fish (beavers, Castor spp.). Some squirrels are known to eat passerine
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s like cardinal
Cardinal (bird)
The Cardinals or Cardinalidae are a family of passerine birds found in North and South America. The South American cardinals in the genus Paroaria are placed in another family, the Thraupidae ....
s and blue jay
Blue Jay
The Blue Jay is a passerine bird in the family Corvidae, native to North America. It is resident through most of eastern and central United States and southern Canada, although western populations may be migratory. It breeds in both deciduous and coniferous forests, and is common near and in...
s.
Size
African Pygmy Mouse
The African Pygmy Mouse, is possibly the smallest of all rodents and one of the smallest mammals. It is widespread within sub-Saharan Africa, and is kept as a pet in other parts of the world...
, Mus minutoides, can be as little as 6 cm (2.4 in) in length and 7 g (0.246917734735784 oz) in weight at maturity, and the Baluchistan Pygmy Jerboa
Baluchistan Pygmy Jerboa
The Baluchistan Pygmy Jerboa, or the Dwarf Three-toed Jerboa, is a species of rodent in the Dipodidae family. It is the only species in the genus Salpingotulus. Adults average only 4.4cm head and body length, with the tail averaging 8cm. Adult females weigh 3.75 grams. It is endemic to Pakistan...
, Salpingotulus michaelis, is of roughly similar or slightly smaller dimensions. On the other hand, the capybara
Capybara
The capybara , also known as capivara in Portuguese, and capibara, chigüire in Venezuela, Colombia, and Ecuador ronsoco in Peru, chigüiro, and carpincho in Spanish, is the largest living rodent in the world. Its closest relatives are agouti, chinchillas, coyphillas, and guinea pigs...
, Hydrochoerus hydrochaeris, usually weighs up to 65 kg although one individual was reported as weighing 91 kg, and the largest known rodent, the extinct Josephoartigasia monesi
Josephoartigasia monesi
Josephoartigasia monesi, an extinct species of South American caviomorph rodent, is the largest rodent known, and lived approximately 4 to 2 million years ago during the Pliocene to early Pleistocene. The species may have weighed , considerably larger than its closest living relative, the pacarana...
, is estimated to have weighed about 1000 kg (2,204.6 lb), and possibly up to 1534 kg (3,381.9 lb) or 2586 kg (5,701.2 lb).
Ecology and use by man
Rodents are important in many ecosystems because they reproduce rapidly, and can function as food sources for predators, mechanisms for seed dispersalSeed dispersal
Seed dispersal is the movement or transport of seeds away from the parent plant. Plants have limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors. Seeds can be dispersed away from the parent plant...
, and as disease vectors. Humans use rodents as a source of fur
Fur
Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to animal...
, as pets, as model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
s in animal testing, for food, and even for detecting landmines
Land mine
A land mine is usually a weight-triggered explosive device which is intended to damage a target—either human or inanimate—by means of a blast and/or fragment impact....
. Due to the wide diversity of their characteristics, some of which are considered uncommon or unique amongst mammals, rodents are used widely in research. For example, the Naked mole rat
Naked Mole Rat
The naked mole rat , also known as the sand puppy or desert mole rat, is a burrowing rodent native to parts of East Africa and the only species currently classified in the genus Heterocephalus...
, Heterocephalus glaber, is the only know mammal that is poikilothermic and also does not produce the neurotransmitter substance P
Substance P
In the field of neuroscience, substance P is a neuropeptide: an undecapeptide that functions as a neurotransmitter and as a neuromodulator. It belongs to the tachykinin neuropeptide family. Substance P and its closely related neuropeptide neurokinin A are produced from a polyprotein precursor...
; it is therefore used in studies on thermoregulation
Thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...
and pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
.
Members of non-rodent orders such as Chiroptera (bats), Scandentia (treeshrew
Treeshrew
The treeshrews are small mammals native to the tropical forests of Southeast Asia. They make up the families Tupaiidae, the treeshrews, and Ptilocercidae, the pen-tailed treeshrews, and the entire order Scandentia. There are 20 species in 5 genera...
s), Soricomorpha
Soricomorpha
The order Soricomorpha is taxon within the class of mammals. In previous years it formed a significant group within the former order Insectivora...
(shrew
Shrew
A shrew or shrew mouse is a small molelike mammal classified in the order Soricomorpha. True shrews are also not to be confused with West Indies shrews, treeshrews, otter shrews, or elephant shrews, which belong to different families or orders.Although its external appearance is generally that of...
s and mole
Mole (animal)
Moles are small cylindrical mammals adapted to a subterranean lifestyle. They have velvety fur; tiny or invisible ears and eyes; and short, powerful limbs with large paws oriented for digging. The term is especially and most properly used for the true moles, those of the Talpidae family in the...
s), Lagomorpha
Lagomorpha
The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families, the Leporidae , and the Ochotonidae...
(hare
Hare
Hares and jackrabbits are leporids belonging to the genus Lepus. Hares less than one year old are called leverets. Four species commonly known as types of hare are classified outside of Lepus: the hispid hare , and three species known as red rock hares .Hares are very fast-moving...
s, rabbit
Rabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...
s and pika
Pika
The pika is a small mammal, with short limbs, rounded ears, and short tail. The name pika is used for any member of the Ochotonidae, a family within the order of lagomorphs, which also includes the Leporidae . One genus, Ochotona, is recognised within the family, and it includes 30 species...
s) and mustelid carnivore
Carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...
s such as weasel
Weasel
Weasels are mammals forming the genus Mustela of the Mustelidae family. They are small, active predators, long and slender with short legs....
s and mink
Mink
There are two living species referred to as "mink": the European Mink and the American Mink. The extinct Sea Mink is related to the American Mink, but was much larger. All three species are dark-colored, semi-aquatic, carnivorous mammals of the family Mustelidae, which also includes the weasels and...
are sometimes confused with rodents.
Evolution
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
record of rodent-like mammals begins shortly after the extinction of the non-avian dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s 65 million years ago, as early as the Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
. Some molecular clock
Molecular clock
The molecular clock is a technique in molecular evolution that uses fossil constraints and rates of molecular change to deduce the time in geologic history when two species or other taxa diverged. It is used to estimate the time of occurrence of events called speciation or radiation...
data, however, suggest that modern rodents (members of the order Rodentia) already appeared in the late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
, although other molecular divergence estimations are in agreement with the fossil record. By the end of the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
epoch, relatives of beavers, dormice
Dormouse
Dormice are rodents of the family Gliridae. Dormice are mostly found in Europe, although some live in Africa and Asia. They are particularly known for their long periods of hibernation...
, squirrels, and other groups appeared in the fossil record. They originated in Laurasia
Laurasia
In paleogeography, Laurasia was the northernmost of two supercontinents that formed part of the Pangaea supercontinent from approximately...
, the supercontinent composed of today's North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, and Asia. Some species colonized Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, giving rise to the earliest hystricognaths
Hystricognathi
Hystricognathi is an infraorder of rodents. Hystricognaths are distinguished from other rodents by the bone structure of their skulls. The masseter medialis passes partially through the infraorbital foramen and connects to the bone on the opposite side...
. From Africa hystricognaths rafted
Rafting event
Oceanic dispersal is a type of biological dispersal that occurs when organisms transfer from one land mass to another by way of a sea crossing on large clumps of floating vegetation. Such matted clumps of vegetation are often seen floating down major rivers in the tropics and washing out to sea,...
to South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, an isolated continent
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
during the Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
and Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
epochs. By the Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
, Africa collided with Asia, allowing rodents such as porcupine
Porcupine
Porcupines are rodents with a coat of sharp spines, or quills, that defend or camouflage them from predators. They are indigenous to the Americas, southern Asia, and Africa. Porcupines are the third largest of the rodents, behind the capybara and the beaver. Most porcupines are about long, with...
s to spread into Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
. During the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
, rodent fossils appeared in Australia. Although marsupial
Marsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
s are the most prominent mammals in Australia, rodents now make up almost 25% of the continent's mammal species. Meanwhile, the Americas became joined by the Isthmus of Panama
Isthmus of Panama
The Isthmus of Panama, also historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country of Panama and the Panama Canal...
and some rodents participated in the resulting Great American Interchange
Great American Interchange
The Great American Interchange was an important paleozoogeographic event in which land and freshwater fauna migrated from North America via Central America to South America and vice versa, as the volcanic Isthmus of Panama rose up from the sea floor and bridged the formerly separated continents...
; sigmodontines
Sigmodontinae
The subfamily Sigmodontinae 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 Tylomyinae as part of a larger definition of Sigmodontinae. When those genera are included, the species count...
surged southward and caviomorphs
Caviomorpha
Caviomorpha is the rodent infraorder or parvorder that unites all South American hystricognaths. It is supported by both fossil and molecular evidence.-Origin:...
headed north.
Some prehistoric rodents
- CastoroidesCastoroidesCastoroides, or Giant Beaver, is an extinct genus of enormous beavers that lived in North America during the Pleistocene. There are two known species:*Castoroides leiseyorum...
, a giant beaverBeaverThe beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world... - Ceratogaulus, a horned burrowing rodent
- Spelaeomys, a rat that grew to a large size on the island of FloresFloresFlores is one of the Lesser Sunda Islands, an island arc with an estimated area of 14,300 km² extending east from the Java island of Indonesia. The population was 1.831.000 in the 2010 census and the largest town is Maumere. Flores is Portuguese for "flowers".Flores is located east of Sumbawa...
- Giant hutiaGiant hutiaThe giant hutias are an extinct group of large rodents known from fossil and subfossil material in the West Indies. One species, Amblyrhiza inundata, is estimated to have weighed between , big specimens being as large as an American Black Bear...
s, a group of rodents once found in the West Indies - IschyromysIschyromysIschyromys is an extinct genus of rodent from North America.The 60 cm long creature is one of the oldest rodents known. It resembled a mouse and already had characteristic rodent incisors. Ischyromyss hind legs were longer than the forelegs, which could be used for other means than walking...
, a primitive squirrelSquirrelSquirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots , flying squirrels, and prairie dogs. Squirrels are indigenous to the Americas, Eurasia, and Africa and have been introduced to Australia...
-like rodent - Leithia, a giant dormouseDormouseDormice are rodents of the family Gliridae. Dormice are mostly found in Europe, although some live in Africa and Asia. They are particularly known for their long periods of hibernation...
- Neochoerus pinckneyiNeochoerus pinckneyiNeochoerus pinckneyi was a North American species of capybara. While capybaras originated in South America, formation of the Isthmus of Panama three million years ago allowed some of them to migrate north as part of the Great American Interchange...
, a large North American capybaraCapybaraThe capybara , also known as capivara in Portuguese, and capibara, chigüire in Venezuela, Colombia, and Ecuador ronsoco in Peru, chigüiro, and carpincho in Spanish, is the largest living rodent in the world. Its closest relatives are agouti, chinchillas, coyphillas, and guinea pigs...
that weighed 100 kg (220.5 lb) - Josephoartigasia monesiJosephoartigasia monesiJosephoartigasia monesi, an extinct species of South American caviomorph rodent, is the largest rodent known, and lived approximately 4 to 2 million years ago during the Pliocene to early Pleistocene. The species may have weighed , considerably larger than its closest living relative, the pacarana...
, the largest known rodent, with an estimated weight of very roughly 1000 kg (2,204.6 lb) - Phoberomys pattersoniPhoberomys pattersoniPhoberomys pattersoni is an extinct rodent that lived in the ancient Orinoco River delta approximately 8 million years ago. It was the second-largest of the roughly 7 species of its genus. Like many other rodents, Phoberomys was a herbivore with high-crowned premolars and molars...
, the second largest known rodent, with an estimated weight of 700 kg (1,543.2 lb) - TelicomysTelicomysTelicomys is an extinct genus of rodent from South America.With a length of more than in T. gigantissimus, it contains two or three of the largest rodents that ever lived, along with Phoberomys, Josephoartigasia, and the giant beaver...
, another giant South American rodent
Classification
Standard classification
The rodents are part of the cladeClade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
s Glires
Glires
Glires is a clade consisting of rodents and lagomorphs . This hypothesis that these form a monophyletic group has been long debated based on morphological evidence, although recent morphological studies strongly support monophyly of Glires...
(along with lagomorphs
Lagomorpha
The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families, the Leporidae , and the Ochotonidae...
), Euarchontoglires
Euarchontoglires
Euarchontoglires is a clade of mammals, the living members of which are rodents, lagomorphs, treeshrews, colugos and primates .-Evolutionary relationships:...
(along with lagomorphs
Lagomorpha
The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families, the Leporidae , and the Ochotonidae...
, primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
s, treeshrew
Treeshrew
The treeshrews are small mammals native to the tropical forests of Southeast Asia. They make up the families Tupaiidae, the treeshrews, and Ptilocercidae, the pen-tailed treeshrews, and the entire order Scandentia. There are 20 species in 5 genera...
s, and colugo
Colugo
Colugos are arboreal gliding mammals found in South-east Asia. There are just two extant species, which make up the entire family Cynocephalidae and order Dermoptera. They are the most capable of all gliding mammals, using flaps of extra skin between their legs to glide from higher to lower...
s), and Boreoeutheria
Boreoeutheria
Boreoeutheria is a clade of placental mammals that is composed of the sister taxa Laurasiatheria and Euarchontoglires...
(along with most other placental
Eutheria
Eutheria is a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from noneutherians by various features of the feet, ankles, jaws and teeth...
mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s). The order Rodentia may be divided into suborders, infraorders, superfamilies
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
and families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
.
Classification scheme:
ORDER RODENTIA (from Latin, rodere, to gnaw)
- Suborder AnomaluromorphaAnomaluromorphaAnomaluromorpha is the name given to a clade that unites the anomalures with the springhare. It has alternately been designated as either a suborder or infraorder...
-
-
- Family Anomaluridae: scaly-tailed squirrels
- Family PedetidaePedetidaePedetidae is a family of mammals from the rodent order. The two living species, the springhares, are distributed throughout much of southern Africa and also around Kenya, Tanzania and Uganda. Fossils have been found as far north as Turkey. Together with the anomalures, Pedetidae forms the suborder...
: springhares
-
-
- Suborder CastorimorphaCastorimorphaCastorimorpha is the suborder of rodents containing the beavers, the pocket gophers, and the kangaroo rats and mice.-Taxonomy:*Suborder Castorimorpha**Superfamily Castoroidea***Family †Eutypomyidae***Family Castoridae - beavers...
-
- Superfamily Castoroidea
- Family CastoridaeCastoridaeThe family Castoridae contains the two living species of beaver and their fossil relatives. This was once a highly diverse group of rodents, but is now restricted to a single genus, Castor.- Characteristics :...
: beaverBeaverThe beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...
s
- Family Castoridae
- Superfamily GeomyoideaGeomyoideaGeomyoidea is a superfamily of rodent that contains the pocket gophers , the kangaroo rats and mice , and their fossil relatives.-Characteristics:...
- Family Geomyidae: pocket gophers (true gophers)
- Family HeteromyidaeHeteromyidaeThe family of rodents that include kangaroo rats, kangaroo mice and rock pocket mice is the Heteromyidae family. Most heteromyids live in complex burrows within the deserts and grasslands of western North America, though species within the Heteromys and Liomys genera are also found in forests and...
: kangaroo ratKangaroo ratKangaroo rats, genus Dipodomys, are small rodents native to North America. The common name derives from their bipedal form: as they hop in a manner similar to the much larger kangaroo, although they are not related...
s and kangaroo miceKangaroo mouseA kangaroo mouse is either one of the two species of jumping mouse native to the deserts of the Southwestern United States, predominantly found in the state of Nevada. Although native to the deserts in the southwest they have been plentiful in Missouri and Pennsylvania...
- Superfamily Castoroidea
-
- Suborder HystricomorphaHystricomorphaThe term Hystricomorpha has had many definitions throughout its history. In the broadest sense it refers to any rodent with a hystricomorphous zygomasseteric system. This includes the Hystricognathi, Ctenodactylidae, Anomaluridae, and Pedetidae...
-
-
- Family incertae sedis DiatomyidaeDiatomyidaeDiatomyidae is a family of hystricomorphous, sciurognathous rodents found in Asia. It is currently represented by a single known living species, Laonastes aenigmamus.- "Lazarus effect" :...
: Laotian rock rat
- Family incertae sedis Diatomyidae
-
- Infraorder CtenodactylomorphiCtenodactylomorphiCtenodactylomorphi is an infraorder of rodent's suborder Hystricomorpha. To that infraorder belongs only one familyCtenodactylidae Gervais, 1853....
-
- Family Ctenodactylidae: gundis
-
- Infraorder HystricognathiHystricognathiHystricognathi is an infraorder of rodents. Hystricognaths are distinguished from other rodents by the bone structure of their skulls. The masseter medialis passes partially through the infraorbital foramen and connects to the bone on the opposite side...
-
- Family Bathyergidae: African mole rats
- Family Hystricidae: Old World porcupines
- Family Petromuridae: dassie rat
- Family Thryonomyidae: cane rats
- Parvorder CaviomorphaCaviomorphaCaviomorpha is the rodent infraorder or parvorder that unites all South American hystricognaths. It is supported by both fossil and molecular evidence.-Origin:...
- Family †Heptaxodontidae: giant hutias
- Family Abrocomidae: chinchilla rats
- Family Capromyidae: hutias
- Family CaviidaeCaviidaeThe cavy family is a family of rodents native to South America, and including the domestic guinea pig, wild cavies, and the capybara, among other animals...
: cavies, including guinea pigGuinea pigThe guinea pig , also called the cavy, is a species of rodent belonging to the family Caviidae and the genus Cavia. Despite their common name, these animals are not in the pig family, nor are they from Guinea...
s and the capybaraCapybaraThe capybara , also known as capivara in Portuguese, and capibara, chigüire in Venezuela, Colombia, and Ecuador ronsoco in Peru, chigüiro, and carpincho in Spanish, is the largest living rodent in the world. Its closest relatives are agouti, chinchillas, coyphillas, and guinea pigs... - Family ChinchillidaeChinchillidaeThe family Chinchillidae contains the chinchillas, viscachas, and their fossil relatives. They are restricted to southern and western South America, often in association with the Andes. They are large rodents, weighing from to , with strong hind legs and large ears...
: chinchillaChinchillaChinchillas are crepuscular rodents, slightly larger and more robust than ground squirrels, and are native to the Andes mountains in South America. Along with their relatives, viscachas, they make up the family Chinchillidae....
s and viscachaViscachaViscachas or vizcachas are rodents of two genera in the family Chinchillidae. They are closely related to chinchillas, and look similar to rabbits...
s - Family Ctenomyidae: tuco-tucoTuco-tucoThe tuco-tucos are members of a group of rodents that belong to the family Ctenomyidae. The tuco-tucos belong to a single genus: Ctenomys, but they include some 60 different species. The relationships among the species are debated by taxonomists. Their closest relatives are degus and other...
s - Family DasyproctidaeDasyproctidaeDasyproctidae is a family of large South American rodents, comprising the agoutis and acouchis. Their fur is a reddish or dark colour above, with a paler underside. They are herbivorous, often feeding on ripe fruit that falls from trees...
: agoutis - Family Cuniculidae: pacas
- Family DinomyidaeDinomyidaeDinomyidae was once a very speciose group of South American hystricognath rodent, but now contains only a single living species, the Pacarana. The Dinomyidae included among its ranks the largest rodents known to date, the bison-sized Josephoartigasia monesi and the smaller Josephoartigasia magna...
: pacaranas - Family Echimyidae: spiny rats
- Family Erethizontidae: New World porcupines
- Family Myocastoridae: nutria, coypu
- Family OctodontidaeOctodontidaeThe Octodontidae are a family of rodents, restricted to south-western South America. Thirteen species of octodontid are recognised, arranged in nine genera. The best known species is the Degu, Octodon degus....
: octodonts
-
-
- Suborder MyomorphaMyomorphaSuborder Myomorpha contains 1,137 species of mouse-like rodents, nearly a quarter of all mammal species. Included are mice, rats, gerbils, hamsters, lemmings and voles. They are grouped according to the structure of the jaw and the structure of the molar teeth. Both their medial and lateral...
-
- Superfamily DipodoideaDipodoideaDipodoidea is a superfamily of rodents that includes Jumping mice and Jerboas....
- Family DipodidaeDipodidaeThe Dipodidae, or dipodids, are a family of rodents found across the northern hemisphere. This family includes over 50 species among the 16 genera....
: jerboas and jumping mice
- Family Dipodidae
- Superfamily MuroideaMuroideaMuroidea is a large superfamily of rodents. It includes hamsters, gerbils, true mice and rats, and many other relatives. They occupy a vast variety of habitats on every continent except Antarctica. Some authorities have placed all members of this group into a single family, Muridae, due to...
- Family Calomyscidae: mouse-like hamsters
- Family CricetidaeCricetidaeThe Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, and New World rats and mice...
: hamsterHamsterHamsters are rodents belonging to the subfamily Cricetinae. The subfamily contains about 25 species, classified in six or seven genera....
s, New World rats and miceNew World rats and miceThe 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 Baiomys to the large Kunsia...
, voleVoleA vole is a small rodent resembling a mouse but with a stouter body, a shorter hairy tail, a slightly rounder head, smaller ears and eyes, and differently formed molars . There are approximately 155 species of voles. They are sometimes known as meadow mice or field mice in North America...
s - Family MuridaeMuridaeMuridae is the largest family of mammals. It contains over 600 species found naturally throughout Eurasia, Africa, and Australia. They have been introduced worldwide. The group includes true mice and rats, gerbils, and relatives....
: true miceMouseA mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
and ratRatRats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s, gerbilGerbilA gerbil is a small mammal of the order Rodentia. Once known simply as "desert rats", the gerbil subfamily includes about 110 species of African, Indian, and Asian rodents, including sand rats and jirds, all of which are adapted to arid habitats...
s, spiny mice, crested rat - Family NesomyidaeNesomyidaeNesomyidae is a family of African rodents in the large and complex superfamily Muroidea. It includes several subfamilies, all of which are native to either continental Africa or to Madagascar...
: climbing mice, rock mice, white-tailed rat, Malagasy rats and mice - Family Platacanthomyidae: spiny dormice
- Family SpalacidaeSpalacidaeThe Spalacidae, or spalacids are a family of rodents in the large and complex superfamily Muroidea. They are native to eastern Asia, the Horn of Africa, the Middle East, and south-eastern Europe. It includes the blind mole rats, bamboo rats, root rats, and zokors...
: mole rats, bamboo rats, and zokorZokorZokors are Asiatic burrowing rodents resembling mole rats. They include two genera, Myospalax and Eospalax. Zokors are native to much of China, Kazhakstan, and Siberian Russia....
s
- Superfamily Dipodoidea
-
- Suborder SciuromorphaSciuromorphaThe term Sciuromorpha has referred to numerous groups of rodents, but the only family common to all variations is the Sciuridae, the squirrels. Most definitions also include the Mountain Beaver....
-
-
- Family Aplodontiidae: mountain beaverMountain BeaverThe Mountain Beaver is the most primitive extant rodent. Not to be confused with the North American beaver Castor canadensis, or its relative the Eurasian beaver, Castor fiber, it has several common names including Aplodontia, Boomer, Ground Bear, and Giant Mole...
- Family Gliridae (also Myoxidae, Muscardinidae): dormiceDormouseDormice are rodents of the family Gliridae. Dormice are mostly found in Europe, although some live in Africa and Asia. They are particularly known for their long periods of hibernation...
- Family Sciuridae: squirrelSquirrelSquirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots , flying squirrels, and prairie dogs. Squirrels are indigenous to the Americas, Eurasia, and Africa and have been introduced to Australia...
s, including chipmunkChipmunkChipmunks are small striped squirrels native to North America and Asia. They are usually classed either as a single genus with three subgenera, or as three genera.-Etymology and taxonomy:...
s, prairie dogPrairie dogPrairie dogs are burrowing rodents native to the grasslands of North America. There are five different species of prairie dogs: black-tailed, white-tailed, Gunnison's, Utah and Mexican prairie dogs. They are a type of ground squirrel, found in the United States, Canada and Mexico...
s, & marmotMarmotThe marmots are a genus, Marmota, of squirrels. There are 14 species in this genus.Marmots are generally large ground squirrels. Those most often referred to as marmots tend to live in mountainous areas such as the Alps, northern Apennines, Eurasian steppes, Carpathians, Tatras, and Pyrenees in...
s
- Family Aplodontiidae: mountain beaver
-
-
Alternative classifications
The above taxonomyTaxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
uses the shape of the lower jaw
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
(sciurognath
Sciurognathi
Sciurognathi is a suborder of rodents that includes squirrels, chipmunks, beavers, and many types of mice. The group is characterized by a specific shape to the lower jaw. In sciurognaths, the angular process of the jaw is in the same plane as the root of the incisors...
or hystricognath
Hystricognathi
Hystricognathi is an infraorder of rodents. Hystricognaths are distinguished from other rodents by the bone structure of their skulls. The masseter medialis passes partially through the infraorbital foramen and connects to the bone on the opposite side...
) as the primary character. This is the most commonly used approach for dividing the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
into suborders. Many older references emphasize the zygomasseteric system
Zygomasseteric system
The zygomasseteric system in rodents is the anatomical arrangement of the masseter muscle of the jaw and the zygomatic arch of the skull...
(suborders Protrogomorpha, Sciuromorpha
Sciuromorpha
The term Sciuromorpha has referred to numerous groups of rodents, but the only family common to all variations is the Sciuridae, the squirrels. Most definitions also include the Mountain Beaver....
, Hystricomorpha
Hystricomorpha
The term Hystricomorpha has had many definitions throughout its history. In the broadest sense it refers to any rodent with a hystricomorphous zygomasseteric system. This includes the Hystricognathi, Ctenodactylidae, Anomaluridae, and Pedetidae...
, and Myomorpha
Myomorpha
Suborder Myomorpha contains 1,137 species of mouse-like rodents, nearly a quarter of all mammal species. Included are mice, rats, gerbils, hamsters, lemmings and voles. They are grouped according to the structure of the jaw and the structure of the molar teeth. Both their medial and lateral...
).
Several molecular phylogenetic
Molecular phylogeny
Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...
studies have used gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
sequences to determine the relationships among rodents, but these studies are yet to produce a single consistent and well-supported taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
. Some clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
s have been consistently produced such as:
- Ctenohystrica contains:
- Ctenodactylidae (gundis)
- HystricognathiHystricognathiHystricognathi is an infraorder of rodents. Hystricognaths are distinguished from other rodents by the bone structure of their skulls. The masseter medialis passes partially through the infraorbital foramen and connects to the bone on the opposite side...
containing:- Hystricidae
- An unnamed cladeCladeA clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
containing:- PhiomorphaPhiomorphaThe rodent parvorder or infraorder Phiomorpha comprises several living and extinct families found wholly or largely in Africa. Along with the Anomaluromorpha and perhaps the †Zegdoumyidae, they represent one of the few early colonizations of Africa by rodents....
- CaviomorphaCaviomorphaCaviomorpha is the rodent infraorder or parvorder that unites all South American hystricognaths. It is supported by both fossil and molecular evidence.-Origin:...
- Phiomorpha
- An unnamed cladeCladeA clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
contains:- Gliridae
- Sciuroidea containing:
- Aplodontiidae
- Sciuridae
- Myodonta includes:
- DipodoideaDipodoideaDipodoidea is a superfamily of rodents that includes Jumping mice and Jerboas....
- MuroideaMuroideaMuroidea is a large superfamily of rodents. It includes hamsters, gerbils, true mice and rats, and many other relatives. They occupy a vast variety of habitats on every continent except Antarctica. Some authorities have placed all members of this group into a single family, Muridae, due to...
- Dipodoidea
The positions of the Castoridae
Castoridae
The family Castoridae contains the two living species of beaver and their fossil relatives. This was once a highly diverse group of rodents, but is now restricted to a single genus, Castor.- Characteristics :...
, Geomyoidea
Geomyoidea
Geomyoidea is a superfamily of rodent that contains the pocket gophers , the kangaroo rats and mice , and their fossil relatives.-Characteristics:...
, Anomaluridae, and Pedetidae
Pedetidae
Pedetidae is a family of mammals from the rodent order. The two living species, the springhares, are distributed throughout much of southern Africa and also around Kenya, Tanzania and Uganda. Fossils have been found as far north as Turkey. Together with the anomalures, Pedetidae forms the suborder...
are still being debated.
Monophyly or polyphyly?
In 1991, a paper submitted to Nature proposed that caviomorphCaviomorpha
Caviomorpha is the rodent infraorder or parvorder that unites all South American hystricognaths. It is supported by both fossil and molecular evidence.-Origin:...
s should be reclassified as a separate order (similar to Lagomorpha
Lagomorpha
The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families, the Leporidae , and the Ochotonidae...
), based on an analysis of the amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
sequences of guinea pig
Guinea pig
The guinea pig , also called the cavy, is a species of rodent belonging to the family Caviidae and the genus Cavia. Despite their common name, these animals are not in the pig family, nor are they from Guinea...
s. This hypothesis was refined in a 1992 paper, which asserted the possibility that caviomorphs may have diverged from myomorph
Myomorpha
Suborder Myomorpha contains 1,137 species of mouse-like rodents, nearly a quarter of all mammal species. Included are mice, rats, gerbils, hamsters, lemmings and voles. They are grouped according to the structure of the jaw and the structure of the molar teeth. Both their medial and lateral...
s prior to later divergences of Myomorpha; this would mean caviomorphs, or possibly hystricomorph
Hystricomorpha
The term Hystricomorpha has had many definitions throughout its history. In the broadest sense it refers to any rodent with a hystricomorphous zygomasseteric system. This includes the Hystricognathi, Ctenodactylidae, Anomaluridae, and Pedetidae...
s, would be moved out of the rodent classification into a separate order. A minority scientific opinion briefly emerged arguing that guinea pig
Guinea pig
The guinea pig , also called the cavy, is a species of rodent belonging to the family Caviidae and the genus Cavia. Despite their common name, these animals are not in the pig family, nor are they from Guinea...
s, degu
Degu
The degu is a small caviomorph rodent that is endemic to central Chile.It is sometimes referred to as the brush-tailed rat, and is also called the common degu, to distinguish it from the other members of the genus Octodon. Other members are also called degus, but they are distinguished by...
s, and other caviomorphs are not rodents, while several papers were put forward in support of rodent monophyly
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
. Subsequent studies published since 2002, using wider taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
and gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
samples, have restored consensus among mammalian biologists that the order Rodentia is monophyletic.
Further reading
- Carleton, M. D. and G. G. Musser. 2005. "Order Rodentia," pp. 745–752 in Mammal Species of the World: A Taxonomic and Geographic Reference. Johns Hopkins University Press, Baltimore.
- David Lambert and the Diagram Group. The Field Guide to Prehistoric Life. New York: Facts on File Publications, 1985. ISBN 0-8160-1125-7
- McKenna, Malcolm C., and Bell, Susan K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp. ISBN 0-231-11013-8
- Nowak, R. M. 1999. Walker's Mammals of the World, Vol. 2. Johns Hopkins University Press, London.
- University of California Museum of Paleontology (UCMP). 2007 "Rodentia". http://www.ucmp.berkeley.edu/mammal/rodentia/rodentia.html
- Wilson, D. E. and D. M. Reeder, eds. 2005. Mammal Species of the World: A Taxonomic and Geographic Reference. Johns Hopkins University Press, Baltimore.
External links
- Website on African rodentia
- Rodent Photos
- Rodent Pests chapter in United States Environmental Protection Agency and University of FloridaUniversity of FloridaThe University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
/Institute of Food and Agricultural SciencesInstitute of Food and Agricultural SciencesThe University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
National Public Health Pesticide Applicator Training Manual - Can Rodents be trained not to gnaw?