Reconstruction of Reithroparamys by Biarmosuchus.

Belongs within: Glires.
Contains: Castorimorpha, Anomaluromorpha, Myomorpha, Hystricomorpha, Gliroidea, Aplodontoidea, Sciuridae.

The Rodentia are the largest of the traditionally recognised 'orders' of mammals, including such animals as rats, mice, squirrels, porcupines and guinea pigs. The group as a whole is characterised by the possession of open-rooted incisors that grow continuously, repairing wear caused by tough plant foods. Rodents are first known from the upper Palaeocene, where they are represented by basal forms such as the Ischyromyidae. Many early rodents have been classified in the family Paramyidae but it is generally agreed that such as a group is paraphyletic, including taxa both outside the rodent crown clade and on the stems of individual rodent subgroups.

Rodents have been classified in the past on the basis of the jaw morphology and musculature (see here). The earliest rodents were 'protrogomorphs', in which the medial masseter muscle was small and originated around the middle of the zygomatic arch; in most living rodents, the origin of this muscle has moved forward on the skull. In the 'sciuromorphs', the medial masseter muscle does not pass through the infraorbital foramen, whereas it does in the more derived 'hystricomorphs' and 'myomorphs'. Each of these arrangements has probably evolved on more than one occasion.

Synapomorphies (from Meng et al. 2003): Incisors with double-layered enamel with Hunter-Schreger bands; talonid of p4 tricuspate; upper cheek teeth widening posteriorly; upper molar crown quadrate; distinctive precingulum along anterior edge of tooth; mesostyle present on molars; mure present. Angular process on mandible bending inward. Posterior edge of anterior zygomatic root anterior to M1.

<==Rodentia [Protrogomorpha, Sciurognathi]
    |--+--+--Paradjidaumo MHL03
    |  |  `--Castorimorpha FS15
    |  `--+--Anomaluromorpha FS15
    |     `--+--Cricetops MHL03
    |        `--Myomorpha FS15
    `--+--+--Reithroparamys debequensis B74, W68
       |  `--+--Rapamys B74
       |     `--Hystricomorpha FS15
       `--+--Ischyromyidae [Ischyromyoidea] J88
          |    |--Ischyromys MHL03
          |    `--Acritoparamys atavus MJ11, MHL03
          `--Sciuromorpha OB13
               |--Gliroidea MR03
               `--Sciuroidea SSH04
                    |--Prosciurus B74
                    |--Mytonomys B74
                    |--Aplodontoidea SSH04
                    `--Sciuridae MR03

Rodentia incertae sedis:
  Ivanantonia efremovi MHL03
  Eucricetodon MHL03
  Ardynomys MHL03
  Titanotheriomys MHL03
  Leptotomus MHL03
  Steneofiber C77
    |--S. nebrascensis C77
    |--S. pansus Cope 1874 C77
    `--S. viciacensis C77
  Chalicomys C77
  Dipodillus BP87
    |--D. maghrebi BP87
    `--D. zakariai BP87
  Sparnacomys Hartenberger 1971 SL00
  Massillamys Tobien 1954 SL00
  Hartenbergeromys Escarguel 1998 SL00
  Allophaiomys pliocaenicus ME05
  Ungaromys Kormos 1932 ME05, P04
    `--U. nanus ME05
  Adelomys [Pseudosciuridae] W68
    `--A. siderolithicus W68
  Aeluravus [incl. Megachiromyoides Weigelt 1933] S62
  Myopotamus coypus MM66
  Trilophomys Depéret 1892 [Trilophomyidae] P04
    |--T. depereti Fejfar 1961 P04
    `--+--T. pyrenaicus (Depéret 1892) [incl. T. schaubi Fejfar 1961] P04
       `--T. vandeweedi Brandy 1979 P04
  Puertoricomys corozalus FS01, AC98
  Clidomys FS01
    |--C. osborni AC98
    `--C. parvus AC98
  Zegdoumys [Zegdoumyidae] GH99
    `--Z. sbetlai Vianey-Liaud et al. 1994 GH99
  Hesperomys nuttalli B75
  Gymnoptychus T23b
    |--G. minimus T23b
    `--G. minor T23b
  Pauromys Troxell 1923 T23a
    `--*P. perditus Troxell 1923 T23a
  Tillomys T23a
  Diplolophus Troxell 1923 T23b
    |--*D. insolens Troxell 1923 T23b
    `--D. parvus Troxell 1923 T23b
  Ischyrotomus V66
  Microparamys W68 [Microparamyidae, Microparamyinae J88]
    `--M. lysitensis W68
  Plesiarctomys Bravard 1850 C77
    |--P. anduns C77
    |--P. buccatus Cope 1876 C77
    |--P. delicatissimus (Leidy 1871) [=Paramys delicatissimus] C77
    `--P. gervaisii C77
  Arctomys bobac C01
  Oligospermophilus douglassi OB13
  Talahphiomys lavocati OB13
  Ceratogaulus Matthew 1902 D07
    |--C. anecdotus D07
    |--C. hatcheri D07
    |--C. minor D07
    `--C. rhinoceros D07
  Phoberomys Sánchez-Villagra, Aguilera & Horovitz 2003 D07
    `--P. pattersoni D07
  Sciuravus [Sciuravidae] MHL03

*Type species of generic name indicated


[AC98] Alcover, J. A., X. Campillo, M. Macias & A. Sans. 1998. Mammal species of the world: additional data on insular mammals. American Museum Novitates 3248: 1–29.

[B75] Bowles, J. B. 1975. Distribution and biogeography of mammals of Iowa. Special Publications, The Museum, Texas Tech University 9: 1–184.

[B74] Bugge, J. 1974. The cephalic arterial system in insectivores, primates, rodents and lagomorphs, with special reference to the systematic classification. Acta Anatomica 87 (Suppl 62): 1–160.

[BP87] Burton, J. A., & B. Pearson. 1987. Collins Guide to the Rare Mammals of the World. Collins: London.

[C77] Cope, E. D. 1877. Report upon the extinct Vertebrata obtained in New Mexico by parties of the expedition of 1874. Geographical Surveys West of the One Hundredth Meridian 4 (2): i–iv, 1–370.

[C01] Csiki, E. 1901. Utivázlat [Reiseskizze]. In: Horváth, G. (ed.) Zichy Jenő Gróf Harmadik Ázsiai Utazása [Dritte Asiatische Forschungsreise des Grafen Eugen Zichy] vol. 2. Zichy Jenő Gróf Harmadik Ázsiai Utazásának Állattani Eredményei [Zoologische Ergebnisse der Dritten Asiatischen Forschungsreise des Grafen Eugen Zichy] pp. xii–xli. Victor Hornyánszky: Budapest, and Karl W. Hierseman: Leipzig.

[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.

[FS15] Faurby, S., & J.-C. Svenning. 2015. A species-level phylogeny of all extant and late Quaternary extinct mammals using a novel heuristic-hierarchical Bayesian approach. Molecular Phylogenetics and Evolution 84: 14–26.

[FS01] Flannery, T., & P. Schouten. 2001. A Gap in Nature: Discovering the World’s Extinct Animals. Text Publishing: Melbourne.

[GH99] Gheerbrant, E., & J.-L. Hartenberger. 1999. Nouveau mammifère insectivore (?Lipotyphla, ?Erinaceomorpha) de l’Eocène inférieur de Chambi (Tunisie). Paläontologische Zeitschrift 73 (1–2): 143–156.

[J88] Jaeger, J.-J. 1988. Rodent phylogeny: new data and old problems. In: Benton, M. J. (ed.) The Phylogeny and Classification of the Tetrapods vol. 2. Mammals pp. 177–199. Clarendon Press: Oxford.

[MHL03] Meng, J., Y. Hu & C. Li. 2003. The osteology of Rhombomylus (Mammalia, Glires): implications for phylogeny and evolution of Glires. Bulletin of the American Museum of Natural History 275: 1–247.

[MR03] Mercer, J. M., & V. L. Roth. 2003. The effects of Cenozoic global change on squirrel phylogeny. Science 299: 1568–1572.

[MJ11] Meredith, R. W., J. E. Janečka, J. Gatesy, O. A. Ryder, C. A. Fisher, E. C. Teeling, A. Goodbla, E. Eizirik, T. L. L. Simão, T. Stadler, D. L. Rabosky, R. L. Honeycutt, J. J. Flynn, C. M. Ingram, C. Steiner, T. L. Williams, T. J. Robinson, A. Burk-Herrick, M. Westerman, N. A. Ayoub, M. S. Springer & W. J. Murphy. 2011. Impacts of the Cretaceous terrestrial revolution and KPg extinction on mammal diversification. Science 334: 521–524.

[MM66] Mivart, S. G. J., & J. Murie. 1866. On the anatomy of the crested agouti (Dasyprocta cristata, Desm.). Proceedings of the Zoological Society of London 1866: 383–417.

[ME05] Moullé, P.-E., A. Echassoux, F. Lacombat, E. Desclaux & S. Bailon. 2005. L’environnement animal des premiers habitants de l’Europe méditerranéenne: les grands mammifères contemporains de l’homme du Vallonnet, données taxonomiques et biostratigraphiques pour la deuxième moitie du Pléistocène inférieur. BAR International Series 1364: 105–113.

[OB13] O'Leary, M. A., J. I. Bloch, J. J. Flynn, T. J. Gaudin, A. Giallombardo, N. P. Giannini, S. L. Goldberg, B. P. Kraatz, Z.-X. Luo, J. Meng, X. Ni, M. J. Novacek, F. A. Perini, Z. S. Randall, G. W. Rougier, E. J. Sargis, M. T. Silcox, N. B. Simmons, M. Spaulding, P. M. Velazco, M. Weksler, J. R. Wible & A. L. Cirranello. 2013. The placental mammal ancestor and the post-K–Pg radiation of placentals. Science 339: 662–667.

[P04] Popov, V. V. 2004. Pliocene small mammals (Mammalia, Lipotyphla, Chiroptera, Lagomorpha, Rodentia) from Muselievo (north Bulgaria). Geodiversitas 26 (3): 403–491.

[S62] Simons, E. L. 1962. A new Eocene primate genus, Cantius, and a revision of some allied European lemuroids. Bulletin of the British Museum (Natural History): Geology 7 (1): 1–36.

[SSH04] Steppan, S. J., B. L. Storz & R. S. Hoffmann. 2004. Nuclear DNA phylogeny of the squirrels (Mammalia: Rodentia) and the evolution of arboreality from c-myc and RAG1. Molecular Phylogenetics and Evolution 30: 703–719.

[SL00] Sudre, J., & G. Lecomte. 2000. Relations et position systématique du genre Cuisitherium Sudre et al., 1983, le plus dérivé des artiodactyles de l’Éocène inféreur d’Europe. Geodiversitas 22 (3): 415–432.

[T23a] Troxell, E. L. 1923a. Pauromys perditus, a small rodent. American Journal of Science 5: 155–156.

[T23b] Troxell, E. L. 1923b. Diplolophus, a new genus of rodents. American Journal of Science 5: 157–159.

[V66] Van Valen, L. 1966. Deltatheridia, a new order of mammals. Bulletin of the American Museum of Natural History 132 (1): 1–126.

[W68] Wood, A. E. 1968. The African Oligocene Rodentia. Peabody Museum of Natural History, Yale University, Bulletin 28: 23–105.

Last updated: 24 July 2018.


  1. Am I mistaken, or are the myomorphs missing altogether from that tree?

    PS. That mountain beaver it teh cutezt!

  2. The myomorphs aren't missing, they're just hidden. According to the tree in Bininda-Emonds et al. (2007) (the most recent source I've gotten through so far), the myomorphs are nested among the hystricomorphs (in the broad sense of Hystricognathi + Anomaluromorpha). When I get the Hystricomorpha entry up, you should see some myomorphs appear as if by magic :)

  3. Ah, thanks for the explanation.


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