This order includes some extremely fast mammals such as the antelopes and pronghorns. It also contains some of the larger and slower moving mammals such as hippos and pigs.
The order contains 10 families and about 220 species.
The name for this order comes from the Greek ἄρτιος - ártios means, "even", and δάκτυλος, dáktylos meaning "finger/toe". Thus, the translation of the artiodactyl is "even toed". Members of this family walk on either 2 or 4 toes. Species like the deer, elk, moose, camels and cows walk on two toes. Species like the pigs and peccaries walk on 4 toes.
We have not listed extinct animals here, but it should be noted that there are several species in this group than no longer exist today. Many of them, like the hell-pigs were huge animals that became the dominant carnivores in their area.

Links:
[1] http://www.untamedscience.com/biodiversity/animals/chordates/mammals/even-toed-ungulates/bovids
[2] http://www.untamedscience.com/biodiversity/animals/chordates/mammals/even-toed-ungulates/camels-llamas
[3] http://www.untamedscience.com/biodiversity/animals/chordates/mammals/even-toed-ungulates/cervids
[4] http://www.untamedscience.com/biodiversity/animals/chordates/mammals/even-toed-ungulates/pigs