PROBOSCIDEAN

Indian elephant (Elephas maximus). African elephant (Loxodonta africana). (order Proboscidea), member of a mammalian order that contains the largest living land mammals, the elephants, and their extinct relatives. The group includes nearly 300 species divided among three suborders, the extinct Deinotherioidea, the extinct Mastodontoidea, and the Elephantoidea, in which are classed the Asian elephant (Elephas maximus; see photograph) and the African elephant (Loxodonta africana; see photograph), the only species still extant. The major features of the order are the elongated snout, ivory tusks, columnlike legs, and large, heavyset bodies. The snout, composed of the upper lip, nostrils, and palate, forms a long, boneless proboscis usually called a trunk. In more recent forms this trunk is both long and strong; it can be used for manipulating small pieces of food or for pulling over living trees. Elephants drink by sucking up water with the trunk and then squirting it into the mouth. They may walk across rivers underwater with just the tip of the trunk protruding so that they can breathe. In living proboscideans the tusks are formed from the second upper incisors. They may reach 3.5 m (11.5 feet) in length. In some extinct forms there were also lower tusks, and some groups (such as the deinotherioids) lost the upper tusks completely; Deinotherium evolved downward-pointing tusks on the end of the mandible. Canine teeth are typically absent or greatly reduced throughout the Proboscidea. The molars in living forms are high-crowned teeth with a grinding surface composed of transverse ridges of enamel; these teeth are replaced from behind as they wear down. The African elephant (Loxodonta) is the larger of the two extant species. Bulls may weigh 5,400 kg (6 tons) and stand 3.3 m tall at the shoulder; cows are somewhat shorter. The largest on record was a bull standing 4 m tall with an estimated weight of 9,000 kg. The tusks appear on both sexes. In Loxodonta the trunk has a corrugated surface and ends in two fingerlike projections, and the ears are huge, frequently 1 m across. In contrast, the Asian or Indian elephant (Elephas) has relatively small ears and a smooth trunk with a single projection at the tip, and only the bulls grow tusks; in the Ceylonese race, even 90 percent of the bulls are tuskless. The Indian elephant has shorter legs than its African counterpart, and its eyes are noticeably smaller. The ridging on the upper surface of the molars is finer and more complex in the Asian species. The top of the head is quite domed in Elephas, whereas it is flattened and the forehead more convex in Loxodonta. Proboscideans first appeared in the Paleocene Epoch (66.4 to 57.8 million years ago). Their ancestors are unknown but are presumed to have been small, about the size of pigs. Various members of the order have inhabited Europe, Asia, Africa, and North and South America. The genus Cuvieronius may have lived in South America as recently as AD 200400, and mastodons are thought to have survived into historical times in North America. The mammoths (Mammuthus), of the suborder Elephantoidea, survived until about 10,000 years ago; hunting by man was probably among the causes of their extinction. The largest stood over 4.2 m at the shoulder. The woolly mammoth (M. primigenius), among the most specialized members of the family Elephantidae, inhabited the cold subarctic areas of the Northern Hemisphere. It was about the same height as the Asian elephant, but its body was shorter and the hindquarters sloped strongly downward. In adaptation to the cold it had very small ears, a short tail, short dense hair with a longer, bristly outer coat, and a layer of subcutaneous fat covering the body. Elephants are quite social and usually live in herds. Among Asian elephants, 10 to 15 females and their young form the core of the herd and travel under the guidance of an old cow. The overall herd leader is a dominant male. Other males may serve the herd as scouts. Female members of a herd are usually related by blood and may remain together for many years, as elephants in the wild have an average life span of perhaps 60 years. Young males move to the periphery of the herd after about 6 or 7 years. One or more individuals stand guard while the rest of the herd is bathing or feeding. If a herd member is injured, others surround it and help it to stay upright and to move away from danger. Orphaned calves are adopted by other females in the herd. Elephants are totally herbivorous, eating grasses, leaves, and the bark of trees. Asian elephants are very fond of wild rice and the wood apple (Feronia elephantorum), and the African species enjoys the fruit of certain palm trees. During droughts Loxodonta obtains some water from the spongy tissues of the baobab tree. There is little courtship before mating among proboscideans. The gestation period may last from 20 to 22 months. The herd surrounds and protects the mother during parturition. Within two hours of birth the calf is able to stand and suckle; it uses the mouth to nurse, not the trunk. The calf weighs about 90 kg (200 pounds) and is 1 m tall at birth; it is born with a sparse coat of brown and yellow hair. Ordinarily there is a four-year interval between calves. Elephants have long been valued for the ivory of their tusks, and many populations are in danger of extermination due to the demand for this material. They have also been used as work animals, especially in India and the surrounding areas. Because they do not breed well in captivity, elephant drives are often held to capture young animals; previously trained elephants are used to subdue and help train the newly captured individuals. Indian elephant (Elephas maximus). African elephant (Loxodonta africana). any member of the order Proboscidea, which comprises three suborders and about 300 species of terrestrial mammals. All but two species, the Asiatic, or Asian, elephant (Elephas maximus; see photograph) and the African elephant (Loxodonta africana; see photograph), are extinct. The elephants are the largest surviving land animals and, among the mammals, are exceeded only by the whales in size. The Proboscidea are characterized by columnar limbs, bulky bodies, and elongated snouts. In recent forms, testes are internal. The snout is a long boneless proboscis, or trunk; it is a combination of the upper lips, palate, and nostrils. Some of the incisor teeth develop into tusks. One extinct suborder (Deinotherioidea) lost the upper tusks; certain others have lost the lower ones and evolved upper tusks of dentine from which the enamel has partially or completely disappeared. The canine teeth were generally repressed in all groups, and the cheek teeth developed rows of blunt cones or ridges. In later forms, the temporary teeth were replaced by permanent ones, which are pushed by an escalator-like movement along a horizontal plane, so that the front teeth were replaced by teeth moving forward from the rear. The skull, which originally was elongated, became shorter, higher, and bulkier in later forms. The back of the eye orbit remained open instead of forming a complete bony ring, and the nasal opening in all Proboscidea is at a higher horizontal plane than the eye sockets. The neck shortened as the animals evolved larger, higher bodies and an elongated trunk that also functions as a hand. The skull has enlarged out of proportion to the brain in order to serve as an anchor for the trunk and to support the heavy dentition. This order occurs in all the continents except Australia. Fossils of proboscideans provide valuable information about early humans who were their contemporaries. Additional reading L.S. De Camp, Elephant (1964), suitable for both the specialist and nonspecialist alike; Richard Carrington, Elephants: A Short Account of Their Natural History, Evolution and Influence on Mankind (1958), an excellent study of living as well as extinct forms; P.E.P. Deraniyagala, Elephas maximus, the Elephant of Asia (1951), with a considerable amount of information on the Asian elephant; and Some Extinct Elephants, Their Relatives, and the Two Living Species (1955), reviewed by G. Gaylord Simpson, a remarkable miscellany of elephant lore and observation, ancient and recent; Henry F. Osborn, Proboscidea, 2 vol. (193642), a comprehensive pioneering work; A.S. Romer, Vertebrate Paleontology, 3rd ed. (1966), a sine qua non for students of proboscidean evolution; and Ivan T. Sanderson, The Dynasty of Abu: A History and Natural History of the Elephants and Their Relatives, Past and Present (1962), a good all-around work. Paul E. Pieris Deraniyagala