Caviomorpha
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2008-03-04T22:48:55Z
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{{Taxobox
| name = Caviomorphs
| fossil_range = [[Oligocene]] - Recent
| image = ph-animals-capybara-2.jpg
| image_width = 200px
| image_caption = [[Capybara]]
| regnum = [[Animal]]ia
| phylum = [[Chordata]]
| classis = [[Mammal]]ia
| ordo = [[Rodent]]ia
| subordo = [[Hystricomorpha]]
| infraordo = [[Hystricognathi]]
| parvordo = '''Caviomorpha'''
| parvordo_authority = Wood, 1955
| subdivision_ranks = Families
| subdivision =
[[Erethizontidae]]<br>
[[Dasyproctidae]]<br>
[[Agoutidae]]<br>
†[[Eocardiidae]]<br>
[[Dinomyidae]]<br>
[[Caviidae]]<br>
[[Octodontidae]]<br>
[[Ctenomyidae]]<br>
[[Echimyidae]]<br>
[[Myocastoridae]]<br>
[[Capromyidae]]<br>
†[[Heptaxodontidae]]<br>
[[Chinchillidae]]<br>
†[[Neoepiblemidae]]<br>
[[Abrocomidae]]
}}
'''Caviomorpha''' is the [[rodent]] [[infraorder]] or [[parvorder]] that unites all '''South American hystricognaths'''. It is supported by both [[fossil]] and [[molecular phylogeny|molecular]] evidence.
==Origin==
The first known rodent [[fossil]] 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 [[flotsam]].
The most common hypothesis suggests that the ancestor to all modern caviomorphs migrated 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 "[[Franimys|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, 2000). 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 or another Old World continent at a similar time. Many researchers think that these two colonizations may be part of the same [[biogeographic]] event.
==Diversity==
Caviomorph rodents underwent an explosive diversification upon arrival into South America. They managed to outcompete other animals in rodent-like [[ecological niche|niche]]s such as certain [[Ameridelphia|South American marsupials]]. Retaining a predominantly [[herbivore|herbivorous]] diet, they expanded their size range to encompass a range from [[rat]]-sized [[Echimyidae|echimyids]] to the [[bison]]-sized ''[[Phoberomys]]''. Meanwhile ecologies included burrowing [[pocket gopher|gopher]]-like forms such as [[tuco-tuco]]s, [[arboreal]] forms such as [[New World porcupine|porcupines]] and certain [[spiny rat]]s, running forms such as [[mara]]s and [[aquatic animal|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 [[acouchi]]s).
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 (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.
==Families==
*'''Infraorder Caviomorpha - New World hystricognaths'''
**†''[[Luribayomys]]'' - ''[[incertae sedis]]''
**Superfamily [[Erethizontoidea]]
***Family [[Erethizontidae]] - New World porcupines
**Superfamily [[Cavioidea]]
***†''[[Scotamys]]''
***[[Dasyproctidae]] - agoutis and acouchis
***[[Agoutidae]] - pacas
***†[[Eocardiidae]]
***[[Dinomyidae]] - pacarana
***[[Caviidae]] - [[Caviinae|cavies]], [[capybara]]s, and [[Mara (mammal)|maras]]
**Superfamily [[Octodontoidea]]
***†''[[Morenella]]'' - ''incertae sedis''
***†''[[Plateomys]]'' - ''incertae sedis''
***†''[[Dicolpomys]]'' - ''incertae sedis''
***†''[[Caviocricetus]]'' - ''incertae sedis''
***[[Octodontidae]] - degus and relatives
***[[Ctenomyidae]] - tuco-tucos
***[[Echimyidae]] - spiny rats
***[[Myocastoridae]] - nutria
***[[Capromyidae]] - hutias
***†[[Heptaxodontidae]] - giant hutias
**Superfamily [[Chinchilloidea]]
***[[Chinchillidae]] - chinchillas and viscachas
***†[[Neoepiblemidae]]
***[[Abrocomidae]] - chinchilla rats
Note that some changes to this taxonomy have been suggested by [[molecular phylogeny|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.
==References==
*Huchon, D. E. J. P. Douzery. 2001. From the Old World to the New World: A molecular chronicle of the phylogeny and biogeography of hystricognath rodents. Molecular Phylogenetics and Evolution, 20:238-251.
*Jenkins, P. D., C. W. Kilpatrick, M. F. Robinson, and R. J. Timmins. 2004. Morphological and molecular investigations of a new family, genus and species of rodent (Mammalia: Rodentia: Hystricognatha) from Lao PDR. Systematics and Biodiversity, 2:419-454.
*Lavocat, R. 1969. La systématique des rongeurs hystricomorphes et la dérive des continents. C. R. Acad. Sci. Paris Sér. D., 269:1496-1497.
*Marivaux, L. M. Vianey-Liaud, and J.-J. Jaeger. 2004. High-level phylogeny of early Tertiary rodents: dental evidence. Zoological Journal of the Linnean Society, 142:105-134.
*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
*Opazo, J.C. 2005. A molecular timescale for caviomorph rodents (Mammalia, Hystricognathi). Molecular Phylogenetics and Evolution, 37: 932-937.
*Wood, A. E. 1985. The relationships, origin, and dispersal of hystricognath rodents. Pp 475-513 in Evolutionary relationships among rodents, a multidisciplinary approach (W. P. Luckett and J.-R. Hartenberger, eds.). Plenum Press, New York.
==See also==
*[[Phiomorpha]]
*[[Hystricomorpha]]
*[[Hystricognathi]]
[[Category:Rodents]]
[[Category:Hystricognath rodents]]
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