Everything about Artiodactyla totally explained
The
even-toed ungulates form the
mammal order Artiodactyla. They are
ungulates whose weight is borne (if they've more than two toes) about equally by the third and fourth toes, rather than mostly or entirely by the third as in
perissodactyls. Another key distinguishing feature is the shape of the
astragalus (a bone in the
hock joint), which has a double-pulley structure in artiodactyls, giving the foot greater flexibility.
There are about 220 artiodactyl
species, including many that are of great nutritional,
economic and cultural importance to humans.
Evolution
As with many animal groups, even-toed ungulates first appeared during the Early
Eocene
(about 54 million years ago). In form they were rather like today's
chevrotains: small, short-legged creatures that ate
leaves and the soft parts of
plants. By the Late Eocene (46 million years ago), the three modern suborders had already developed:
Suina (the
pig group);
Tylopoda (the
camel group); and
Ruminantia (the
goat and
cattle group). Nevertheless, artiodactyls were far from dominant at that time: the
odd-toed ungulates (ancestors of today's
horses and
rhinos) were much more successful and far more numerous. Even-toed ungulates survived in niche roles, usually occupying marginal
habitats, and it's presumably at that time that they developed their complex
digestive systems, which allowed them to survive on lower-grade food.
The appearance of
grasses during the
Eocene and their subsequent spread during the
Miocene (about 20 million years ago) saw a major change: grasses are very difficult to eat and the even-toed ungulates with their highly-developed
stomachs were better able to adapt to this coarse, low-
nutrition diet, and soon replaced the odd-toed ungulates as the dominant
terrestrial herbivores. Now-extinct Artiodactyla which developed during the
Miocene include the species
Ampelomeryx,
Tauromeryx,
Triceromeryx, and others.
Suina
Suina (
pigs and
peccaries) are artiodactyls that retain four toes of fairly equal size, have simpler
molars, short legs, and often have enlarged
canine teeth that form
tusks. In general, they're
omnivores and have a simple stomach, except for the two hippopotamus species and the
babirusa which are herbivores. Hippopotamidae have been considered a member of Suina, however, recent morphological and genetic research suggests that hippos are more closely related to whales.
Camelids and Ruminantia
Camelids and
Ruminantia tend to be longer-legged, to walk on only the central two toes (though the outer two may survive as rarely-used dew-claws) and to have more complex cheek teeth well-suited to grinding up tough grasses. They have evolved a highly developed digestive process in which partly-digested food is
regurgitated and re-chewed (
chewing the cud or
cudding). This complex digestion takes place in a multi-chambered stomach, the
rumen itself. It allows them to use
fermentation by
microorganisms to digest
cellulose, a plant material which animals can't digest directly.
Classification
Further Information
Get more info on 'Artiodactyla'.
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