Hystricomorpha
Encyclopedia
The term Hystricomorpha (from Latin hystrix, "porcupine" and Greek morphē "form") has had many definitions throughout its history. In the broadest sense it refers to any rodent (except dipodoids
) with a hystricomorphous zygomasseteric system
. This includes the Hystricognathi
, Ctenodactylidae, Anomaluridae, and Pedetidae
. Molecular and morphological results suggest that the inclusion of the Anomaluridae and Pedetidae in Hystricomorpha may be suspect. Based on , these two families are treated here as representing a distinct suborder Anomaluromorpha
.
The modern definition of Hystricomorpha also known as Entodacrya or Ctenohystrica is a taxonomic hypothesis uniting the gundi
s with the hystricognath rodents. There is considerable morphological
support for this relationship and strong molecular
support. If true, this hypothesis renders the traditional view of Sciurognathi
invalid as it becomes a paraphyletic group.
The hystricomorph rodents, or at least members of Caviomorpha
, are sometimes regarded as non-rodents. Most molecular and genetic research however confirms the monophyly
of rodents. Support for rodent polyphyly
appears to be a product of long branch attraction
.
Hystricomorph rodents appeared in South America
in the early Oligocene, a continent which previously had metatheria
ns, xenarthra
ns, and meridiungulates
as the only resident non-flying mammals. They apparently arrived by rafting
across the Atlantic
from Africa
. The same type of migration may have occurred with primates, which also appeared in South America before the Great American Interchange
. All of this is still controversial, and new scientific discoveries on this subject are published regularly.
of and who subjected a number of early fossil rodents to parsimony
analysis and recovered support for the Hystricomorpha or Entodacrya hypothesis. Their results rendered the suborder Sciuravida as defined by to be polyphyletic and invalid. The symbol "†" is used to indicate extinct groups.
Dipodoidea
Dipodoidea is a superfamily of rodents that includes Jumping mice and Jerboas....
) with a hystricomorphous 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...
. This includes the Hystricognathi
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...
, Ctenodactylidae, 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...
. Molecular and morphological results suggest that the inclusion of the Anomaluridae and Pedetidae in Hystricomorpha may be suspect. Based on , these two families are treated here as representing a distinct suborder Anomaluromorpha
Anomaluromorpha
Anomaluromorpha 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...
.
Classification
Gundi
Gundis are a group of small, stocky rodents found in Africa. They live in rocky deserts across the northern parts of the continent. The family comprises 4 living genera and 5 species , as well as numerous extinct genera and species...
s with the hystricognath rodents. There is considerable morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
support for this relationship and strong 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...
support. If true, this hypothesis renders the traditional view of Sciurognathi
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...
invalid as it becomes a paraphyletic group.
The hystricomorph rodents, or at least members of Caviomorpha
Caviomorpha
Caviomorpha is the rodent infraorder or parvorder that unites all South American hystricognaths. It is supported by both fossil and molecular evidence.-Origin:...
, are sometimes regarded as non-rodents. Most molecular and genetic research however confirms the 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...
of rodents. Support for rodent polyphyly
Polyphyly
A polyphyletic group is one whose members' last common ancestor is not a member of the group.For example, the group consisting of warm-blooded animals is polyphyletic, because it contains both mammals and birds, but the most recent common ancestor of mammals and birds was cold-blooded...
appears to be a product of long branch attraction
Long branch attraction
Long branch attraction is a phenomenon in phylogenetic analyses when rapidly evolving lineages are inferred to be closely related, regardless of their true evolutionary relationships. For example, in DNA sequence-based analyses, the problem arises when sequences from two lineages evolve rapidly...
.
Hystricomorph rodents appeared 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...
in the early Oligocene, a continent which previously had metatheria
Metatheria
Metatheria is a grouping within the animal class Mammalia. First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon Marsupialia though it is slightly wider since it also contains the nearest fossil relatives of marsupial mammals.The earliest known...
ns, xenarthra
Xenarthra
The superorder Xenarthra is a group of placental mammals , existent today only in the Americas and represented by anteaters, tree sloths, and armadillos. The origins of the order can be traced back as far as the Paleogene in South America...
ns, and meridiungulates
Meridiungulata
Meridiungulata is an extinct clade with the rank of cohort or super-order, containing the South-American ungulates: Pyrotheria , Astrapotheria, Notoungulata and Litopterna...
as the only resident non-flying mammals. They apparently arrived by rafting
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
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...
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...
. The same type of migration may have occurred with primates, which also appeared in South America before 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...
. All of this is still controversial, and new scientific discoveries on this subject are published regularly.
Families
The following list of families is based on the 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...
of and who subjected a number of early fossil rodents to parsimony
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
analysis and recovered support for the Hystricomorpha or Entodacrya hypothesis. Their results rendered the suborder Sciuravida as defined by to be polyphyletic and invalid. The symbol "†" is used to indicate extinct groups.
- Suborder Hystricomorpha
- Superfamily Ctenodactyloidea
- Ctenodactylidae - gundis
- †Tammquammyidae
- 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 RatLaotian rock ratThe 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... - †Yuomyidae
- †Chapattimyidae
- Hystricognathiformes
- †TsaganomyidaeTsaganomyidaeTsaganomyidae is an extinct family of rodents from Asia. It contains three genera. Tsaganomyids are generally considered to be related to the Hystricognathi...
- 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...
- true hystricognaths- †"Baluchimyinae"
- Hystricidae - Old World porcupines
- 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....
- †MyophiomyidaeMyophiomyidaeThe Myophiomyids are an extinct family of Old World hystricognaths....
- †DiamantomyidaeDiamantomyidaeDiamantomyidae is a family of extinct hystricognath rodents from Africa and Asia....
- †PhiomyidaePhiomyidaeThe Phiomyidae are a family of prehistoric rodents from Africa and Eurasia. A 2011 study placed Gaudeamus in a new family, gaudeamuridae.Genera include:* Acritophiomys* Andrewsimys* Elwynomys* Gaudeamus* Phiomys...
- †KenyamyidaeKenyamyidaeThe Kenyamyidae are an extinct family of rodents from Africa....
- Petromuridae - Dassie Rat
- Thryonomyidae - cane rats
- Bathyergidae - blesmols
- †Bathyergoididae
- †Myophiomyidae
- CaviomorphaCaviomorphaCaviomorpha is the rodent infraorder or parvorder that unites all South American hystricognaths. It is supported by both fossil and molecular evidence.-Origin:...
- New World hystricognaths- Superfamily Erethizontoidea
- Erethizontidae - New World porcupines
- Superfamily Cavioidea
- †CephalomyidaeCephalomyidaeCephalomyidae is an extinct family of caviomorph rodents from South America. The specific relationships of the family are uncertain, and affinities to both chinchilloid and cavioid rodents have been supported...
- 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 - Cuniculidae - 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...
- cavies, capybaras and guinea pigs
- †Cephalomyidae
- Superfamily Octodontoidea
- 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
- Octodontidae
- 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
- Superfamily Erethizontoidea
- †Tsaganomyidae
- Superfamily Ctenodactyloidea