Caviomorpha
Encyclopedia
Caviomorpha is the rodent
infraorder or parvorder that unites all South American hystricognaths
. It is supported by both fossil
and molecular
evidence.
in South America
is represented by an undescribed species from the Late Eocene
/Early Oligocene
deposits. By the late Oligocene
, all superfamilies and most families of caviomorphs are present in the fossil record.
During this time, South America was isolated from all other continent
s. Several hypotheses have been proposed as to how hystricognath rodents colonized this island continent. Most require that a small group of these rodents traveled across ocean bodies atop a raft
of mangrove
s or driftwood
.
The most common hypothesis suggests that the ancestor to all modern caviomorphs rafted
across the Atlantic Ocean
(then narrower) from Africa
(Lavocat, 1969; Huchon and Douzery, 2000). This is supported by molecular results, which suggest that the Phiomorpha
(as restricted to Bathyergidae, Petromuridae, and Thryonomyidae) are sister taxa to the Caviomorpha. In fact, until the discovery of the Laotian Rock Rat
, all modern hystricognath families were restricted to South America, Africa, or had a range that included Africa (Hystricidae).
The principal alternative hypothesis is that the caviomorph ancestor arose in Asia
and migrated to South America through another continent. Most commonly, North America
is cited as the most likely continent (Wood, 1985) as connections between North America and Asia were common via Beringia, and North America appears to have been closer to South America than any other continent at this time. The "Franimorpha" were once proposed as a potential North American rodent group that may represent an ancestor to the Caviomorpha, but most modern researchers consider franimorphs to have been protrogomorphous instead of hystricomorphous.
Fossil evidence suggests the Entodacrya may have originated in Asia (Marivaux et al., 2004) and this is cited as potential evidence for an Asian origin for Caviomorpha as well. Likewise, Jenkins et al. (2005) argue that their discovery of a hystricognath rodent family (Laonastidae) exclusive to Asia may be further evidence for an Asian origin of caviomorphs.
Alternatively, the caviomorphs may have originated in Asia, but traveled through Africa, Australia
and Antarctica, or Africa and Antarctica (noted but not advocated by Huchon and Douzery, 2001). Alternatively they may have originated in Africa and traveled to South America via Antarctica.
New World monkey
s appear to have colonized South America from Africa at a similar time.
s such as certain South American marsupials
. Retaining a predominantly herbivorous
diet, they expanded their size range to encompass a range from rat
-sized echimyids to the bison
-sized Phoberomys. Meanwhile ecologies included burrowing gopher
-like forms such as tuco-tuco
s, arboreal forms such as porcupines
and certain spiny rat
s, running forms such as mara
s and aquatic
forms such as the capybara
and nutria. Habitats range from grasslands (maras), high mountains (chinchillas and chinchilla rat
s), forest edges (prehensile-tailed porcupine
s) and dense tropical forests (paca
s and acouchis).
Although many species of caviomorphs have migrated into Central America
since the Great American Interchange
, only a single living species, the North American Porcupine
, has naturally colonized North America north of Mexico (the extinct capybara Neochoerus pinckneyi
also accomplished this feat). The nutria has been introduced into North America and has proven a highly successful invasive species
there.
Note that some changes to this taxonomy have been suggested by molecular
studies. The Dinomyidae may belong to the Chinchilloidea, the Abrocomidae may belong to the Octodontoidea, and the Hydrochaeridae may have evolved from within the Caviidae.
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
infraorder or parvorder that unites all South American 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...
. It is supported by both fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
and molecular
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...
evidence.
Origin
The first known rodent fossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
in 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...
is represented by an undescribed species from the Late 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...
/Early 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...
deposits. By the late 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...
, all superfamilies and most families of caviomorphs are present in the fossil record.
During this time, South America was isolated from all other 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...
s. Several hypotheses have been proposed as to how hystricognath rodents colonized this island continent. Most require that a small group of these rodents traveled across ocean bodies atop a raft
Raft
A raft is any flat structure for support or transportation over water. It is the most basic of boat design, characterized by the absence of a hull...
of mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
s or driftwood
Driftwood
Driftwood is wood that has been washed onto a shore or beach of a sea or river by the action of winds, tides, waves or man. It is a form of marine debris or tidewrack....
.
The most common hypothesis suggests that the ancestor to all modern caviomorphs 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,...
across the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
(then narrower) from 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...
(Lavocat, 1969; Huchon and Douzery, 2000). This is supported by molecular results, which suggest that the Phiomorpha
Phiomorpha
The 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....
(as restricted to Bathyergidae, Petromuridae, and Thryonomyidae) are sister taxa to the Caviomorpha. In fact, until the discovery of the Laotian Rock Rat
Laotian rock rat
The Laotian rock rat or kha-nyou , sometimes called the "rat-squirrel", is a rodent species of the Khammouan region of Laos. The species was first described in a 2005 article by Paulina Jenkins and coauthors, who considered the animal to be so distinct from all living rodents that they placed it...
, all modern hystricognath families were restricted to South America, Africa, or had a range that included Africa (Hystricidae).
The principal alternative hypothesis is that the caviomorph ancestor arose in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
and migrated to South America through another continent. Most commonly, 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...
is cited as the most likely continent (Wood, 1985) as connections between North America and Asia were common via Beringia, and North America appears to have been closer to South America than any other continent at this time. The "Franimorpha" were once proposed as a potential North American rodent group that may represent an ancestor to the Caviomorpha, but most modern researchers consider franimorphs to have been protrogomorphous instead of hystricomorphous.
Fossil evidence suggests the Entodacrya may have originated in Asia (Marivaux et al., 2004) and this is cited as potential evidence for an Asian origin for Caviomorpha as well. Likewise, Jenkins et al. (2005) argue that their discovery of a hystricognath rodent family (Laonastidae) exclusive to Asia may be further evidence for an Asian origin of caviomorphs.
Alternatively, the caviomorphs may have originated in Asia, but traveled through Africa, 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...
and Antarctica, or Africa and Antarctica (noted but not advocated by Huchon and Douzery, 2001). Alternatively they may have originated in Africa and traveled to South America via Antarctica.
New World monkey
New World monkey
New World monkeys are the five families of primates that are found in Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Platyrrhini parvorder and the Ceboidea superfamily, which are essentially synonymous since...
s appear to have colonized South America from Africa at a similar time.
Diversity
Caviomorph rodents underwent an explosive diversification upon arrival into South America. They managed to outcompete other animals in rodent-like nicheEcological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
s such as certain South American marsupials
Ameridelphia
Ameridelphia is traditionally a superorder that includes all marsupials living in the Americas except for the Monito del Monte...
. Retaining a predominantly herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
diet, they expanded their size range to encompass a range from 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...
-sized echimyids to the bison
Bison
Members of the genus Bison are large, even-toed ungulates within the subfamily Bovinae. Two extant and four extinct species are recognized...
-sized Phoberomys. Meanwhile ecologies included burrowing gopher
Pocket gopher
The pocket gophers are burrowing rodents of the family Geomyidae. These are the "true" gophers, though several ground squirrels of the family Sciuridae are often called gophers as well...
-like forms such as tuco-tuco
Tuco-tuco
The 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, arboreal forms such as porcupines
New World porcupine
The New World porcupines, or Erethizontidae, are large arboreal rodents, distinguished by the spiny covering from which they take their name. They inhabit forests and wooded regions across North America, and into northern South America...
and certain spiny rat
Spiny rat
The spiny rats are a group of hystricognath rodents in the family Echimyidae. They are distributed from central Central America through much of South America. They were also found in the West Indies until the 19th century...
s, running forms such as mara
Mara (mammal)
The maras are a genus of the cavy family. They are the sole representatives of the subfamily Dolichotinae. These large relatives of guinea pigs are common in the Patagonian steppes of Argentina but live in other areas of South America as well such as Paraguay...
s and aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
forms such as 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...
and nutria. Habitats range from grasslands (maras), high mountains (chinchillas and chinchilla rat
Chinchilla rat
Chinchilla rats or chinchillones are members of the family Abrocomidae. This family has few members compared to most rodent families with only 9 known living species. They resemble Chinchillas in appearance, with a similar soft fur and silvery-grey color, but have a body-structure more like a...
s), forest edges (prehensile-tailed porcupine
Prehensile-tailed porcupine
The prehensile-tailed porcupines or Coendous are a group of arboreal porcupine found in Central and South America. They are closely related to the other Neotropical tree porcupines and these three are sometimes treated as subgenera of Coendou instead of distinct genera.-Characteristics:Among the...
s) and dense tropical forests (paca
Paca
The Lowland Paca , also known as the Spotted Paca, is a large rodent found in tropical and sub-tropical America, from East-Central Mexico to Northern Argentina...
s and acouchis).
Although many species of caviomorphs have migrated into Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
since the 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...
, only a single living species, the North American Porcupine
North American Porcupine
The North American Porcupine , also known as Canadian Porcupine or Common Porcupine, is a large rodent in the New World porcupine family. The Beaver is the only rodent larger than the North American Porcupine found in North America...
, has naturally colonized North America north of Mexico (the extinct capybara Neochoerus pinckneyi
Neochoerus pinckneyi
Neochoerus 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...
also accomplished this feat). The nutria has been introduced into North America and has proven a highly successful invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
there.
Families
- Infraorder Caviomorpha - New World hystricognaths
- †Luribayomys - incertae sedisIncertae sedis, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
- Superfamily Erethizontoidea
- Family Erethizontidae - New World porcupines
- Superfamily Cavioidea
- †GuiomysGuiomysGuiomys is an extinct genus of cavioid rodent which existed in west central Patagonia of Argentina, during the middle Miocene. Guiomys is known from mandibular and maxillary fragments with molars, and isolated cheek teeth. It was first named by María E. Pérez in 2010 and the type species is Guiomys...
- †Scotamys
- 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 and acouchis - Agoutidae - pacas
- †EocardiidaeEocardiidaeThe Eocardiidae are an extinct family of caviomorph rodents from South America. The family is probably ancestral to the living family Caviidae , which includes cavies, maras, and capybaras and their relatives...
- 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...
- pacarana - 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...
- caviesCaviinaeCaviinae is a subfamily uniting all living members of the family Caviidae with the exception of the maras, capybaras and Kerodon. The subfamily traditionally contained the guinea pig-like forms along with the cursorially adapted Kerodon...
, 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...
s, and marasMara (mammal)The maras are a genus of the cavy family. They are the sole representatives of the subfamily Dolichotinae. These large relatives of guinea pigs are common in the Patagonian steppes of Argentina but live in other areas of South America as well such as Paraguay...
- †Guiomys
- Superfamily Octodontoidea
- †Caviocricetus - incertae sedis
- †Dicolpomys - incertae sedis
- †Morenella - incertae sedis
- †Plateomys - incertae sedis
- †Tainotherium Turvey, Grady & Rye, 2006 - incertae sedis
- 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....
- degus and relatives - Ctenomyidae - tuco-tucos
- Echimyidae - spiny rats
- Myocastoridae - nutria
- Capromyidae - hutias
- †Heptaxodontidae - giant hutias (probably paraphyletic)
- Superfamily Chinchilloidea
- 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...
- chinchillas and viscachas - †NeoepiblemidaeNeoepiblemidaeThe Neoepiblemidae are an extinct family of hystricognath rodents from South America. The genus Dabbenea, formerly placed here, is now included in Phoberomys...
- Abrocomidae - chinchilla rats
- Chinchillidae
- †Luribayomys - incertae sedis
Note that some changes to this taxonomy have been suggested by molecular
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. The Dinomyidae may belong to the Chinchilloidea, the Abrocomidae may belong to the Octodontoidea, and the Hydrochaeridae may have evolved from within the Caviidae.