The Artiodactyla are also known as the even toed ungulates because they are grazers (ungulates) and they have either two or four toes, which distinguishes them from the Perissodactyls which have either one toe (horses) or three (rhinos). The Artiodactyla represent a large proportion of existing mammals and many of the most important large herbivore species. There are approximately 220 known species worldwide. They are native to all continents except Antarctica and Australia. Many have horns and most have modified stomachs. Most of our important domesticated animal such as pigs, cows, sheep and goats belong to this order.
They are divided into ten families, many of which are immediately recognisable. Pigs belong to the family Suidae. Cattle, sheep, goats and antelope are placed in the family Bovidae. Deer are Cervids, camels belong to the Camelidae, giraffes to the Giraffidae and hippos to the Hippopotamidae. There are also some less well known families: the peccaries (Tayassuidae), chevrotains (Tragulidae), Musk deer (Moschidae) and the Pronghorn (Antilocapridae).
Pigs, peccaries and hippos are fairly closely related and are grouped together in the suborder Suiformes. They share a number of important characteristics besides a tendency to being fat. They have simple stomachs and do not chew their cud (ruminate). They have four toes and tusk-like canine teeth. All three groups are social animals and can be quite dangerous if encountered in the wild. Hippos are adapted for a semi-aquatic lifestyle and are known to kill more people along the Nile River than crocodiles. Even though they are herbivores, they can be very aggressive.
The family of camels and llamas stands alone in their suborder, the Tylopoda, with camels being found in the Old World while llamas, alpacas and guanacos are found in South America. There are two types of old world camels, the single humped dromedary and the two humped Bactrian camel. Camels have a three chambered stomach and chew their cud. They have unfused ankle bones which separates them from the third suborder of Artiodactyls, the Ruminantia. Camels have been domesticated in both the old and new worlds and were important to many cultures as beasts of burden as well as for food, and in the new world, for their wool.
The suborder Ruminantia contains the remaining six families. The most important to humans is undoubtedly the Bovidae. This is quite a diverse family and includes not only the 26 odd species of cows (subfamily Bovinae), but also the duikers (17 species, Cephalophinae), antelopes (24 species, Hippotraginae), gazelles and dwarf antelope (30 species, Antilopinae) and goat antelopes (26 species, Caprinae). They are mostly found on the plains and grasslands of the world and are particularly numerous and diverse in Africa. In America, the great plains were once home to huge numbers of buffalo, whose great herds shaped and sustained the ecosystem and eventually the numerous tribes of plains Indians. Common characteristics of bovids are fused ankles, missing upper incisors and reduced canines . Bovids also have a three or four chambered stomach and chew their cud to increase digestive efficiency.
Another diverse family of ruminants is the Cervidae or deer, which contains almost 40 species world-wide and many important herbivores in both grasslands and forest ecosystems as well as tundra ecosystems in the far north. Deer are characterised by their antlers. In some species they occur in both sexes but in most the antlers are most developed in the males, which use them to establish dominance and mating rights. Reindeer, elk and moose have the most impressive racks of antlers.
The chevrotains are small deer, sometimes known as mouse deer which are found in tropical rain forests across Africa, India and Southeast Asia. There are only four species and they are not well known or studied as they are shy, secretive creatures. They are considered to be intermediate between pigs and deer and have remained unchanged for some 30 million years.
The Musk deer, Moschidae, live in central Asia. There are three species and they are found in mountain forests where they are active at dusk and dawn. Their name comes from the valuable musk that they produce and over-hunting for this product has severely reduced their numbers. They do not have antlers but males have long canines.
The Giraffidae contains not only the giraffes but also the forest dwelling Okapi. Giraffes are superbly evolved for foraging in the highest levels of the canopy and they are one of the most successful herbivores on the African savannah. Their bodies are foreshortened in relation to the extremely long neck and the forelegs are longer than the hind legs. They can run fast but have trouble drinking and have to splay their legs out to reach water. Their necks, interestingly, have no extra bones, but have the same seven cervical bones that we have, just enlarged and elongated. Giraffes are one of the few ruminants that are born with horns.
The American Pronghorn Antelope is different enough from other ruminants to be placed in its own family, the Antilocapridae. They occur in grasslands and are active by day. Their numbers were devastated by hunters but are increasing again with protection, Both sexes have horns which are shed and regrow each year.
It is impossible to cover the amazing diversity of this mammalian order in a single article. They are an example of evolutionary diversification. When the dinosaurs were wiped out, the mammals spread out into all the habitats and empty niches once occupied by the reptiles. Where once dinosaurs grazed, deer and antelope took over. This allowed for the development of the mammalian predators, the Carnivora. The result is the diversity of artiodactyls that we see in the world today. Many species unfortunately are endangered due to human activities, but many are now bred in captivity and protected in national parks. It would be a shame to lose these interesting and beautiful animals.
For more information: http://animaldiversity.ummz.umich.edu/site/accounts/information/Artiodactyla.html