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 †Cephalomyidae 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, or at least members of Caviomorpha, are sometimes regarded as non-rodents (Graur et al., 1991; D'Erchia et al., 1996; Reyes et al., 2000). Most molecular and genetic research however confirms the monophyly of rodents (Cao et al., 1994; Kuma and Miyata, 1994; Sullivan and Swofford, 1997; Robinson-Rechavi et al., 2000; Lin et al., 2002; Reyes et al., 2004). Support for rodent polyphyly appears to be a product of long branch attraction (Bergsten, 2005).

Hystricomorph rodents appeared in South America in the early Oligocene (Flynn et al., 2003), and moved to a continent which previously had marsupials, xenarthrans, and meridiungulates as the only resident non-flying mammals. The same view on early migration might be true to 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.

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
          • †Cephalomyidae
          • Dasyproctidae - agoutis and acouchis
          • Cuniculidae - 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

• Bergsten, J. 2005. A review of long-branch attraction. Cladistics, 21:163-193.
• Cao, Y., Adachi, J., Yano, T. and Hasegawa, M. 1994. Phylogenetic place of guinea pigs: No support of the rodent-polyphyly hypothesis from maximum-likelihood analyses of multiple protein sequences. Molecular Biology and Evolution, 11: 593-604.
• 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.
• D'Erchia, A., Gissi, C., Pesole, G., Saccone, C. and Arnason, U. 1996. The guinea-pig is not a rodent. Nature, 381 (6583): 597-600.
• Flynn, J. J., Wyss, A. R., Croft, D. A., and Charrier, R. 2003. The Tinguiririca Fauna, Chile: biochronology, paleoecology, biogeography, and a new earliest Oligocene South American Land Mammal ‘Age’. Palaeogeography, Palaeoclimatology, Palaeoecology, 195:229-259.
• Graur, D., Hide, W. and Li, W. 1991. Is the guinea-pig a rodent? Nature, 351: 649-652.
• 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.
• Kuma, K. and Miyata, T. 1994. Mammalian phylogeny inferred from multiple protein data. Japanese Journal of Genetics, 69 (5): 555-66.
• 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.
• Lin, Y-H, et al. 2002. Four new mitochondrial genomes and the increased stability of evolutionary trees of mammals from improved taxon sampling. Molecular Biology and Evolution, 19: 2060-2070.
• 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
• Reyes, A., Pesole, G. and Saccone, C. 2000. Long-branch attraction phenomenon and the impact of among-site rate variation on rodent phylogeny. Gene, 259 (1-2): 177-87.
• Reyes, A., Gissi, C., Catzeflis, F., Nevo, E. Pesole, G. and Saccone, C. 2004. Congruent mammalian trees from mitochondrial and nuclear genes using Bayesian methods. Molecular Biology and Evolution, 21 (2): 397-403.
• Robinson-Rechavi, M., Ponger, L. and Mouchiroud, D. 2000. Nuclear gene LCAT supports rodent monophyly. Molecular Biology and Evolution, 17: 1410-1412.
• Sullivan, J. and Swofford, D.L. 1997. Are guinea pigs rodents? the importance of adequate models in molecular phylogenetics. Journal of Mammalian Evolution, 4: 77-86.