Temporal range: Late Cretaceous – Oligocene, 66.5–23 Ma
|Arctocyon, a plantigrade condylarth|
Condylarthra is an order of extinct placental mammals known primarily from the Paleocene and Eocene epochs. Condylarths are among the most characteristic Paleocene mammals and they illustrate the evolutionary level of the Paleocene mammal fauna. When compared to today's mammals, condylarths are relatively unspecialized placental mammals.
The disappearance of the dinosaurs opened up an ecological niche for large mammalian herbivores. Some condylarths evolved to fill the niche, while others remained insectivorous. This may explain, in part, the tremendous evolutionary radiation of the condylarths that we can observe throughout the Paleocene, resulting in the different groups of ungulates (or "hoofed mammals") that form the dominant herbivores in most Cenozoic animal communities on land, except on the island continent of Australia.
Among recent mammals, Paenungulata (hyraxes, elephants, and sea cows), Perissodactyla (horses, rhinoceroses, and tapirs), Artiodactyla (pigs, deer, antelope, cows, camels, hippos, and their relatives), Cetacea (whales), and Tubulidentata (aardvarks) are traditionally regarded as members of the Ungulata. Besides these, several extinct animals also belong to this group, especially the endemic South American orders of ungulates, (Meridiungulata). Although many ungulates have hoofs, this feature does not define the Ungulata. Indeed, some condylarths had small hoofs on their feet, but the most primitive forms are clawed.
Recent molecular and DNA research has reorganised the picture of mammalian evolution. Paenungulates and tubulidentates are seen as Afrotherians, and no longer seen as closely related to the Laurasiatherian perissodactyls, artiodactyls, and cetaceans, implying that hooves were acquired independently (i.e. were analogous) by at least two different mammalian lineages, once in the Afrotheria and once in the Laurasiatheria. Condylarthra itself, therefore, is polyphyletic: the several condylarth groups are not closely related to each other at all. Indeed, Condylarthra is sometimes regarded as a 'wastebasket' taxon. True relationships remain in many cases unresolved.
Condylarthra always was a problematic group. When Condylarthra was first described by Cope 1881, Phenacodontidae was the type and only family therein. Cope 1885, however, raised Condylarthra to an order and included a wide range of diverse placentals with generalized dentitions and postcrania. More recent researchers (i.e. post-WW2) have been more restrictive; either including only a limited number of taxa, or proposing that the term should be abandoned altogether.
- superior ramus of stapedial artery shifted to petrosal or lost
- mastoid foramen lost
- bulla if present composed of ectotympanic
- relatively bunodont teeth with low cusp relief
- trigonids of lower molars shortened anteroposteriorly
- large, posteriorly projecting hypoconulid on M3
- head of astragalus is short and robust
- Family Arctocyonidae
- Family Periptychidae
- Family Hyopsodontidae
- Subfamily Tricuspiodontinae
- Genus Aletodon
- Genus Decoredon
- Genus Dipavali
- Genus Dorraletes
- Genus Haplaletes
- Genus Haplomylus
- Genus Hyopsodus
- Genus Louisina
- Genus Microhyus
- Genus Midiagnus
- Genus Oxyprimus
- Genus Palasiodon
- Genus Paschatherium
- Genus Utemylus
- Genus Yuodon
- Family Mioclaenidae
- Family Phenacodontidae
- Family Didolodontidae
- Family Sparnotheriodontidae?
- Genus Tingamarra?
- Genus Protungulatum
- Genus Kharmerungulatum
|Wikimedia Commons has media related to Condylartha.|
|This article needs additional citations for verification. (January 2010)|
- Cope, E. D. (1881). "A new type of Perissodactyla". American Naturalist 15: 1017–20. OCLC 45953517.
- Cope, E. D. (1885). "The Vertebrata of the Tertiary Formations of the West". U. S. Geological Survey of the Territories 3: 1–1009. OCLC 3934701. Retrieved April 2013.
- Janis, C.M. (1993). "Tertiary Mammal Evolution in the Context of Changing Climates, Vegetation, and Tectonic Events". Annual Review of Ecology and Systematics 24: 467–500. doi:10.1146/annurev.es.24.110193.002343.
- Madsen, O.; Scally, M.; Douady, C.J.; Kao, D.; DeBry, R.W.; Adkins, R.; Amrine, H.M.; Stanhope, M.J.; de Jong, W.W.; Springer, M.S. (2001). "Parallel adaptive radiations in two major clades of placental mammals". Nature 409 (6820): 610–614. doi:10.1038/35054544. PMID 11214318.
- McKenna, M.C.; Bell, S.K. (1997). Classification of Mammals Above the Species Level. Columbia University Press. ISBN 0-231-11012-X.
- Murphy, W.J.; Eizirik, E.; O'Brien, S.J.; Madsen, O.; Scally, M.; Douady, C.J.; Teeling, E.C.; Ryder, O.A.; Stanhope, M.J.; de Jong, W.W.; Springer, M.S. (2001). "Resolution of the early placental mammal radiation using Bayesian phylogenetics". Science 294 (5550): 2348–2351. doi:10.1126/science.1067179. PMID 11743200.
- Novacek, M.J. (1986). "The skull of leptictid insectivorans and the higher-level classification of eutherian mammals". Bulletin of the American Museum of Natural History 183 (1): 1–111. hdl:2246/1628.
- Prothero, D.R.; Manning, E.M.; Fischer, M. (1988). "The phylogeny of the ungulates". In Benton, M. J. The phylogeny and classification of the tetrapods. 2: mammals. Systematics Association Special Volume 35B. Oxford: Clarendon Press. pp. 201–234. ISBN 9780198577126. Retrieved May 2013.
- Thewissen, J.G.M. (1990). Evolution of Paleocene and Eocene Phenacodontidae (Mammalia, Condylarthra). Papers on Paleontology 29. Museum of Paleontology, The University of Michigan. OCLC 742731818.
- Van Valen, L.M. (1966). "Deltatheridia, a new order of mammals". Bulletin of the American Museum of Natural History 132 (1): 1–126. hdl:2246/1126.
- Van Valen, L.M. (1988). "Paleocene dinosaurs or Cretaceous ungulates in South America?". Evolutionary Monographs 10: 1–79.