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Even-toed ungulate
From Wikipedia, the free encyclopedia
Even-toed ungulates
Fossil range:
Early Eocene - Recent
Rocky Mountain
Goat, Oreamnos americanus
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Mammalia
Order:
Artiodactyla
Owen,
1848
Families
Antilocapridae
Bovidae
Camelidae
Cervidae
Giraffidae
Hippopotamidae
Moschidae
Suidae
Tayassuidae
Tragulidae
Leptochoeridae
Chaeropotamidae
Dichobunidae
Cebochoeridae
Entelodontidae
Anoplotheriidae
Anthracotheriidae
Cainotheriidae
Agriochoeridae
Merycoidodontidae
Leptomerycidae
Protoceratidae
Xiphodontidae
Amphimerycidae
Gelocidae
Merycodontidae
Dromomerycidae
The even-toed ungulates
form the mammal order Artiodactyla. They are ungulates whose weight is
borne about equally by the third and fifth toes[citation needed],
rather than mostly or entirely by the third as in perissodactyls. There are
about 220 artiodactyl species, including many that are of great economic
importance to humans.
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 is presumably at
that time that they developed their complex digestive systems, which allowed
them to survive on lower-grade feed.
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.
The artiodactyls fall into
two groups which, despite underlying similarities, are rather different. The
Suina (pigs, hippos, and peccaries) retain four toes, have simpler molars,
short legs, and their canine teeth are often enlarged to form tusks. In
general, they are omnivores and have a simple stomach (the two hippopotamus
species and the babirusa are exceptions). It is possible that Suina is not a
natural group. In particular, recent research suggests that the Hippopotamidae
(which are likely derived from among the extinct group known as anthracotheres)
may be more closely related to the ruminants than to the pigs.
The camelids and the
Ruminantia, on the other hand, tend to be longer-legged, to have only two toes,
to have more complex cheek teeth well-suited to grinding up tough grasses, and
multi-chambered stomachs. Not only are their digestive systems highly
developed, they have also evolved the habit of chewing cud: regurgitating
partly-digested food to chew it again and extract the maximum possible benefit
from the end.
Lastly a group of
artiodactyls, which molecular biology suggests were most closely related to
Hippopotamidae, returned to the sea to become whales. The conclusion is that
Artiodactyla, if it excludes Cetacea, is a paraphyletic group. For this reason,
the term Cetartiodactyla was coined to refer to the group containing
both artiodactyls and whales (though the problem could just as easily be
resolved by recognizing Cetacea as a subgroup of Artiodactyla).
- ORDER ARTIODACTYLA
- Family Dichobunidae
- Family Helohyidae
- Suborder Suina
- Family Suidae: pigs
- Family Hippopotamidae: hippos
- Family Tayassuidae: peccaries
- Suborder Tylopoda
- Family Camelidae: camels and llamas
- Suborder Ruminantia
- Infraorder Tragulina
- Family Tragulidae: chevrotains
- Infraorder Pecora
- Family Moschidae: musk deer
- Family Cervidae: deer
- Family Giraffidae: Giraffe and Okapi
- Family Antilocapridae: pronghorn
- Family Bovidae: cattle, goats, sheep,
and antelope
|
Even-toed ungulates
Fossil range:
Early Eocene - Recent |
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|
Rocky Mountain
Goat, Oreamnos americanus |
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|
Scientific classification |
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Families |
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Antilocapridae |
The even-toed ungulates
form the mammal order Artiodactyla. They are ungulates whose weight is
borne about equally by the third and fifth toes[citation needed],
rather than mostly or entirely by the third as in perissodactyls. There are
about 220 artiodactyl species, including many that are of great economic
importance to humans.
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 is presumably at
that time that they developed their complex digestive systems, which allowed
them to survive on lower-grade feed.
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.
The artiodactyls fall into
two groups which, despite underlying similarities, are rather different. The
Suina (pigs, hippos, and peccaries) retain four toes, have simpler molars,
short legs, and their canine teeth are often enlarged to form tusks. In
general, they are omnivores and have a simple stomach (the two hippopotamus
species and the babirusa are exceptions). It is possible that Suina is not a
natural group. In particular, recent research suggests that the Hippopotamidae
(which are likely derived from among the extinct group known as anthracotheres)
may be more closely related to the ruminants than to the pigs.
The camelids and the
Ruminantia, on the other hand, tend to be longer-legged, to have only two toes,
to have more complex cheek teeth well-suited to grinding up tough grasses, and
multi-chambered stomachs. Not only are their digestive systems highly
developed, they have also evolved the habit of chewing cud: regurgitating
partly-digested food to chew it again and extract the maximum possible benefit
from the end.
Lastly a group of
artiodactyls, which molecular biology suggests were most closely related to
Hippopotamidae, returned to the sea to become whales. The conclusion is that
Artiodactyla, if it excludes Cetacea, is a paraphyletic group. For this reason,
the term Cetartiodactyla was coined to refer to the group containing
both artiodactyls and whales (though the problem could just as easily be
resolved by recognizing Cetacea as a subgroup of Artiodactyla).
- ORDER ARTIODACTYLA
- Family Dichobunidae
- Family Helohyidae
- Suborder Suina
- Family Suidae: pigs
- Family Hippopotamidae: hippos
- Family Tayassuidae: peccaries
- Suborder Tylopoda
- Family Camelidae: camels and llamas
- Suborder Ruminantia
- Infraorder Tragulina
- Family Tragulidae: chevrotains
- Infraorder Pecora
- Family Moschidae: musk deer
- Family Cervidae: deer
- Family Giraffidae: Giraffe and Okapi
- Family Antilocapridae: pronghorn
- Family Bovidae: cattle, goats, sheep,
and antelope