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. However, in comparison to their insectivorous ancestors, members of the Condylarthra show the first signs of specializing to become omnivores or even herbivores.
Since larger land-bound herbivores were absent since the extinction of the dinosaurs, this shift in diet triggered 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.
Here, the term Ungulata refers to a subgroup of placental mammals that are descendants of a common ancestor (i.e. homologous to), the most primitive condylarth. Among recent mammals, Paenungulata (hyraxes, elephants, and sea cows), Perissodactyla (horses, rhinoceri, and tapirs), Artiodactyla (pigs, antelope, 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. Some condylarths indeed have 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 no longer seen as closely related to perissodactyls, artiodactyls, and cetaceans, implying that hooves were acquired independently (i.e. were analogous) by at least two different mammalian lineages. This raises the possibility that Condylarthra itself is polyphyletic: the several condylarth groups may not be related to each other at all. Indeed condylarths are increasingly regarded as a 'wastebasket' taxon, though true relationships remain in many cases unresolved.
In addition to meridiungulates and living ungulates, a condylarthran ancestry has been proposed for several other extinct groups of mammals, including Mesonychia and Dinocerata.
* Family Arctocyonidae
1. ^ a b McKenna, M. C, and S. K. Bell (1997). Classification of Mammals Above the Species Level. Columbia University Press. ISBN 023111012X.
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