The genus Macrauchenia is also an extinct form, constituting a separate family, Macraucheniadæ, peculiar to the later Tertiaries of South America. Its skull is, on the whole, like that of the Horse, but the nasal bones are short and like those of the Tapir. It possessed a long neck, like the Llamas, and a full complement of teeth, partly equine, partly resembling those of Rhinoceros. Both fore and hind feet were furnished with three toes.
W. BOYD DAWKINS.
H. W. OAKLEY.
CHAPTER III.
ARTIODACTYLA—THE PIG OR HOG FAMILY.
Introductory Remarks on the Artiodactyla—Character of their Feet—The Wanting Digit—Comparison of the Bones of the Fore Feet of Representative Animals—Other Characters in the Artiodactyla—Classification—[SUIDÆ, OR HOG FAMILY]—Groups of the Family—Snout—Sense of Smell—Libels—Mention in the Bible—Among the Jews—Range—Teeth—[THE WILD BOAR]—General Features—Habits—Historical Mention—[THE INDIAN HOG]—Habits—A Wild Boar Hunt—A Noble Foe—[THE DOMESTIC HOG]—The “Irish Greyhound Pig”—Effects of Domestication—[THE SOLID-HOOFED BREED OF PIGS]—Description of the Bones of Foot—[MASKED PIG]—[BUSH HOG]—[BABIRUSA]—[THE WART HOGS]—[ÆLIAN’S WART HOG]—[THE ETHIOPIAN WART HOG]—[PECCARIES]—Habits—Dentition—Feet—Species—[THE FOSSIL HOGS].
SUB-ORDER ARTIODACTYLA.
BONES OF THE LEFT FORE LIMB OF (1) COMMON PIG, (2) AFRICAN DEERLET, (3) JAVAN DEERLET, (4) ROEBUCK, (5) COMMON SHEEP, (6) CAMEL.[268]
(From Specimens in the Museum of the Royal College of Surgeons.)
BESIDES the Perissodactyla there is another large group of animals in which the extremities of the fore and hind toes are entirely surrounded by horny tissue in the shape of hoofs. These are the Artiodactyla, or cloven-hoofed animals, which differ from the Perissodactyla in the manner in which the weight of the body is carried upon the feet. In the Artiodactyla the toes are even in number, being four in all the feet, except in the Camel tribe, the Giraffe, and a very few Antelopes, in which only two are present. It is the digit which corresponds to the human thumb in the fore foot, and to the great toe in the hind, which is always deficient, the inner and the outer digits (the second and the fifth) being frequently reduced to but minute rudiments, as in the Sheep and Ox. Some may ask how we know that it is the thumb and the great toe which are missing, and not the little finger or toe, for instance. A glance at the human hand and foot will explain the point. Counting the bones in the thumb or great toe, it will be found that there are but two bones beyond the limit of the “ball of the thumb,” or the free part of the great toe, whilst in all the other fingers and toes three bones can be counted. A reference to Fig. 3 makes it evident that in the Artiodactyla there figured, as in all others, each toe has three bones in it; and as all mammalian animals which have five toes agree with man in possessing one less bone in the inner toe than in any of the others, it is but logical to conclude that when four toes only are present, all possessing an equal number of bones, the one absent is that corresponding to the thumb and great toe. Each foot is always symmetrical in itself, at the same time that its imaginary axis, which is the line drawn down the middle of it, runs between the two medial toes, they corresponding with the third and fourth of the human limb. The accompanying drawings of the bones of the fore-foot of the Pig, the Water Chevrotain (or Deerlet), the Javan Chevrotain, the Roebuck, the Sheep, and the Camel, illustrate, better than can be done by words, the difference in the degree of development of the outer toes found in the group. In the Pig all the four toes are well developed, and there is no consolidation of their constituent elements. In the Water Deerlet of West Africa the external toes are smaller, whilst, as in the Pig, each metacarpal—which is in the human hand the part of each finger included within the palm—is independent of its neighbour, the Javan Deerlet differing in having the third and fourth fused into a “cannon” bone. But in the Red Deer the reduction of the second and fifth digits is so great that their metacarpals are not perfect, being only present in their upper parts; whilst the phalanges, or lower bones, are very small, being reduced in the Sheep to mere bony spots with minute hoofs, which latter are quite absent in the Camel, Llama, Giraffe, and Pronghorn Antelope.
There are numerous other characters which associate these animals, and prove the natural affinities of the different species, at the same time that in geologic times there existed other creatures which fill up the intervals between existing forms, and conclusively demonstrate the manner in which the order has been evolved from a common type in times long past.