Hystricomorpha

Hystricomorpha Fossil range: Eocene - Recent
Capybara
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Rodentia Suborder: Hystricomorpha Brandt, 1855
Families
Ctenodactylidae †Tammquammyidae Diatomyidae †Yuomyidae †Chapattimyidae †Tsaganomyidae †"Baluchimyinae" Hystricidae †Myophiomyidae †Diamantomyidae †Phiomyidae †Kenyamyidae Petromuridae Thryonomyidae Bathyergidae †Bathyergoididae Erethizontidae Dasyproctidae Agoutidae †Eocardiidae Dinomyidae Caviidae Octodontidae Ctenomyidae Echimyidae Myocastoridae Capromyidae †Heptaxodontidae Chinchillidae †Neoepiblemidae Abrocomidae

Skull of a capybara showing the enlarged infraorbital canal present in most members of the Hystricomorpha. This condition is termed hystricomorphy.

The term Hystricomorpha 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 Carleton and Musser (2005), 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 gundis with the hystricognath rodents (Carleton and Musser, 2005). 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 are often being seen as non-rodents, and may instead developed independently on Gondwana and thus being members of the Atlantogenata. Most molecular and genetic research however confirms the monophyly of rodents. As a result, rodents may be very early migrants to South America, and moved to a continent which used to have Marsupials and Xenarthrans as the only native mammals. The same view on early migration might be true to Primates, which also appeared as South American mammals before the Great American Interchange. Note that the position of South American ungulates (Meridiungulata) is still unclear: they might be an independent assemblage, distantly related to Xenarthra. However, they may also represent a very early Laurasiatherian migration to South America, soon to be separated from other Ungulates and developing in their own distinct way. 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 taxonomy of Marivaux et al. (2002; 2004) 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 McKenna and Bell (1997) to be polyphyletic and invalid. The symbol "†" is used to indicate groups where no living members survive.

• Suborder Hystricomorpha
  • Superfamily Ctenodactyloidea
    • Ctenodactylidae - gundis
    • †Tammquammyidae
    • Diatomyidae - Laotian Rock Rat
    • †Yuomyidae
    • †Chapattimyidae
  • Hystricognathiformes
    • †Tsaganomyidae
    • Hystricognathi - true hystricognaths
      • †"Baluchimyinae"
      • Hystricidae - Old World porcupines
      • Phiomorpha
        • †Myophiomyidae
        • †Diamantomyidae
        • †Phiomyidae
        • †Kenyamyidae
        • Petromuridae - Dassie Rat
        • Thryonomyidae - cane rats
        • Bathyergidae - blesmols
        • †Bathyergoididae
      • Caviomorpha - New World hystricognaths
        • Superfamily Erethizontoidea
          • Erethizontidae - New World porcupines
        • Superfamily Cavioidea
          • Dasyproctidae - agoutis and acouchis
          • Agoutidae - pacas
          • †Eocardiidae
          • Dinomyidae - pacarana
          • Caviidae - cavies
        • Superfamily Octodontoidea
          • 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

References

• Carleton, M. D. and G. G. Musser. 2005. Order Rodentia. Pp745-752 in Mammal Species of the World A Taxonomic and Geographic Reference (D. E. Wilson and D. M. Reeder eds.). Baltimore, Johns Hopkins University Press.
• 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.
• Landry, S. O. J. 1999. A proposal for a new classification and nomenclature for the glires. Mitt. Mus. Nat. Kd. Berl. Zool. Reihe, 75:283-316.
• 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.
• Marivaux, L. J. L. Welcomme, M. Vianey-Liaud, and J.J. Jaeger. 2002. The role of Asia in the origin and diversification of hystricognathous rodents. Zoologica Scripta, 31:225-239.
• 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

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