The term Hystricomorpha (from Greek ὕστριξ, hystrix 'porcupine' and Greek μορφή, morphē 'form')[2] 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 the inclusion of the Anomaluridae and Pedetidae in Hystricomorpha may be suspect. Based on
Carleton & Musser 2005, these two families are discussed here as representing a distinct suborder
Anomaluromorpha.
Classification
The modern definition of Hystricomorpha, also known as Entodacrya or Ctenohystrica, is a taxonomic hypothesis uniting the
gundis with the
hystricognath rodents.[3] Considerable
morphological and strong
molecular support exists for this relationship. 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 not regarded as rodents.[4] Most molecular and genetic research, however, confirms the
monophyly of rodents.[5] Support for rodent
polyphyly appears to be a product of
long branch attraction.[6]
Hystricomorph rodents appeared in
South America in the Eocene,[7] a continent which previously had
metatherians,
xenarthrans, and
meridiungulates as the only resident nonflying mammals[citation needed]. They apparently arrived by
rafting across the
Atlantic from
Africa. The same type of migration may have occurred with
primates,[8] which also appeared in South America in the Eocene when it was an isolated continent, long before the
Great American Interchange. All of this is still controversial, and new scientific discoveries on this subject are published regularly.
^Bond, M.; Tejedor, M. F.; Campbell, K. E.; Chornogubsky, L.; Novo, N.; Goin, F. (2015-02-04). "Eocene primates of South America and the African origins of New World monkeys". Nature. 520 (7548): 538–41.
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10.1038/nature14120.
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Carleton, M. D.; Musser, G. G. (2005). "Order Rodentia". In Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World A Taxonomic and Geographic Reference. Baltimore: Johns Hopkins University Press. pp. 745–752.
ISBN978-0-8018-8221-0.
D'Erchia, A.; Gissi, C.; Pesole, G.; Saccone, C.; Arnason, U. (1996). "The guinea-pig is not a rodent". Nature. 381 (6583): 597–600.
doi:
10.1038/381597a0.
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Marivaux, L.; Welcomme, J.-L.; Vianey-Liaud, M.; Jaeger, J.-J. (2002). "The role of Asia in the origin and diversification of hystricognathous rodents". Zoologica Scripta. 31 (3): 225–239.
doi:
10.1046/j.1463-6409.2002.00074.x.
S2CID86358222.
McKenna, M. C.; Bell, S. K. (1997). Classification of Mammals Above the Species Level. New York: Columbia University Press.
ISBN0-231-11013-8.
Reyes, A.; Pesole, G.; Saccone, C. (2000). "Long-branch attraction phenomenon and the impact of among-site rate variation on rodent phylogeny". Gene. 259 (1–2): 177–187.
doi:
10.1016/S0378-1119(00)00438-8.
PMID11163975.