Cetartiodactyl
| Even-toed ungulates Temporal range: 55–0 Ma Early Eocene–Holocene |
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| Even-toed ungulates. While cetaceans such as whales and dolphins are not normal artiodactyls, they belong to the clade; the Artiodactyla are sometimes termed the Cetartiodactyla to reflect this. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Subclass: | Theria |
| Infraclass: | Eutheria |
| (unranked): | Exafroplacentalia |
| Magnorder: | Boreoeutheria |
| Superorder: | Laurasiatheria |
| (unranked): | Scrotifera |
| Order: |
Artiodactyla Owen, 1848 |
| Subclades | |
The even-toed ungulates (Artiodactyla, from Greek ἄρτιος (ártios), meaning 'even', and δάκτυλος (dáktylos), meaning 'finger/toe') are ungulates (hoofed animals) whose weight is borne equally by the third and fourth toes. By contrast, odd-toed ungulates, such as horses, bear their weight primarily on their third toes. The aquatic cetaceans (whales, dolphins, and porpoises) evolved from within even-toed ungulates, so modern taxonomic classification sometimes combines the Artiodactyla and Cetacea into the Cetartiodactyla.
Excluding whales, the roughly 220 artiodactyl species include pigs, peccaries, hippopotamuses, cetaceans, camels, llamas, alpacas, mouse deer, deer, giraffes, antelopes, sheep, goats, and cattle, many of which are of great dietary, economic, and cultural importance to humans.
The oldest fossils of even-toed ungulates date back to the early Eocene (about 53 million years ago). Since these findings almost simultaneously appeared in Europe, Asia, and North America, it is very difficult to accurately determine the origin of artiodactyls. The fossils are classified as belonging to the family Dichobunidae; their best-known and best-preserved member is Diacodexis. These were small animals, some as small as a hare, with a slim build, lanky legs, and a long tail. The hind legs were much longer than the front legs. The early to middle Eocene saw the emergence of the ancestors of most of today's mammals.
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