The Perissodactyla have been brigaded with the Artiodactyla to form the typical group of the ungulates, under the name of Diplarthra, or Ungulata Vera, and the features distinguishing the combined group from the less specialized members of the order Ungulata will be found under the heading of that order.
Orders: Insectivora, Chiroptera, Dermoptera, Edentata (Sub-orders: Xenarthra, Pholidota, Tubulidentata), Rodentia (Sub-orders: Duplicidentata, Simplicidentata), Tillodontia, Carnivora (Sub-orders: Fissipedia, Pinnipedia, Creodonta), Cetacea (Sub orders: Archaeoceti, Odontoceti, Mystacoceti), Sirenia, Ungulata (Sub-orders: Proboscidea, Hyracoidea, Barypoda, Toxodontia, Amblypoda, Litopterna, Ancylopoda, Condylarthra, Perissodactyla, Artiodactyla), Primates (Sub-orders: Prosimiae, Anthropoidea).
ARTIODACTYLA (from Gr.
As contrasted with the Perissodactyla living, and in a great degree extinct, Artiodactyla are characterized by the following structural features.
Artiodactyla date from the Eocene period, when they appear to have been less numerous than the Perissodactyla, although at the present day they are immeasurably ahead of that group, and form indeed the dominant ungulates.
The primitive Artiodactyla thus probably had the typical number (44) of incisor, canine and molar teeth, brachyodont molars, conical odontoid process, four distinct toes on each foot, with metacarpal, metatarsal and all the tarsal bones distinct, and no frontal appendages.
The last section of the Artiodactyla is that of the Suina, represented at the present day by the pigs (Suidae), and the hippopotamuses (Hippopotamidae), and in past times by the Anthracotheriidae, in which may probably be included the Elotheriidae.
Pecus, cattle), a term employed - in a more restricted sense - in place of the older title Ruminantia, to designate the group of ruminating artiodactyle ungulates represented by oxen, sheep, goats, antelopes, deer, giraffes, &c. The leading characteristics of the Pecora are given in some detail in the article Artiodactyla; but it is necessary to allude to a few of these here.
Their lower articular surfaces, instead of being pulley-like, with deep ridges and grooves, as in other Artiodactyla, are simple, rounded and smooth.
Dier, &c., probably from a root dhus-, to breathe), originally the name of one of two British species, the red-deer or the fallow-deer, but now extended to all the members of the family Cervidae, in the section Pecora of the suborder Artiodactyla of the order Ungulata.
Artiodactyla (Ruminants, Swine, &c.).
The latter is represented by the Eocene Condylarthra, which undoubtedly gave rise to the Perissodactyla and Artiodactyla, and probably to most, if not all, of the other groups.
The Artiodactyla are the only group of ungulates known to have been represented in Madagascar; but since both these Malagasy forms - namely two hippopotamuses (now extinct) and a river-hog - are capable of swimming, it is most probable that they reached the island by crossing the Mozambique Channel.