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Elephas maximus, the Asian elephant and Loxodonta africana, the African elephant, are the only surviving species of the family Elephantidae (Class Mammalia, Order Proboscidea). Although African and Asian elephants are two distinct genera, they are generally similar in size, appearance, physiology and social behaviour.

African elephants are further sub-divided into Loxodonta africana africana (savanna or bush elephant) and Loxodonta africana cyclotis (forest elephant), which is smaller than the savanna elephants and are confined to central and west Africa. Recent molecular genetic studies, however, suggest that the African savanna and forest elephants can be classified as two separate species i.e., Loxodonta africana and Loxodonta cyclotis (Roca et al. 2001). The separate taxonomic classification of western African elephants, recently suggested, is yet to be confirmed (Debruyne, et al. 2003).

 Asian elephants are often sub-divided into subspecies based on the regions where they occur. The three main sub-species of Asian elephants recognised traditionally are Elephas maximus maximus (Sri Lankan elephant), Elephas maximus indicus (Asian mainland elephant) and Elephas maximus sumatranus (Sumatran elephant). The recent genetic studies do not support the differentiation of the Sri Lankan and the Asian mainland elephants (Fernando et al. 2000). However, there is some support for considering the elephants of Borneo as an evolutionarily significant unit (Fernando et al. 2003). In certain other traditional classifications, Elephas maximus hirsutus (Malaysia and Thailand) and Elephas maximus burmanicus (Myanmar) are also noted, although there are no scientific data to support these. The Asian elephant (Elephas maximus) is believed to have evolved during the late Pleistocene from Elephas hysudricus, fossil remains of which were discovered in Shiwaliks in northern India.

Ancestry of elephants dates back to millions of years. One of the oldest  fossil evidences available on early elephant relatives are of Moeritherium, whose fossil remains were first discovered near lake Moeris in ancient Egypt. They were about the size of a pig standing 70 cm at the shoulders and looked like a pigmy hippopotamus with a small flexible snout, but without a trunk.
Then came Deinotherium (Gr. deinos, terrible, ther, beast), which evolved in Africa and migrated to Europe and Asia and which had large trunks and two tusks curving downward from the lower jaw. After Deinotheres, large creatures called Gomphotheres evolved in Africa, whose ancestry is traced to the ancient proboscideans and not to Deinotheres. Gomphotheres were long jawed proboscideans, with four tusks two each on upper and lower jaws. Most gomphotheres were about 2 m tall at the shoulders.

Around the time of Deinotheres, a hairy proboscidean called Mammutid or Mastodon (Gr. Masto, breast, odontos, tooth) also existed, which evolved in Africa and subsequently migrated to Eurasia and North America. They had luxurious growth of hairs all over the body. Another difference from the present day elephants was in their molars, with rounded cusps or crus, which were relatively few in number. Their teeth were also described as “horn” shaped. The tusks were long and curved and had flat forehead raising to a prominent domed crown. Mammutids were different from mammoths, which are true elephants.

A parallel line of elephantoids called Stegodons (Gr. Stegos, roof) or gabble toothed elephants evolved, which were the earliest pan Asian elephantoids. One of the Stegodon species had tusks, which grew closely parallel to each other, diverged at the tip. The long tusks reached the ankles of the beasts. Trunk was narrow and literally squeezed between the tusks. Until recently, the stegodons were thought to be ancestors of the mammoths and modern elephants, but now we know that they had evolved in Asia, while the true elephants originated in Africa.

Another proboscidean ancestry goes to Platybelodons, which were with very short trunks and four tusks with the lower tusk flattened as the name implies (Gr. Platys, broad). Hence they are also known as the shovel tuskers. The flat lower tusks helped to dig and scoop vegetation. 

Palaeomastodon, another proboscidean ancestor that evolved in Africa and spread to Eurasia, were the immediate ancestors of mastodons. Palaeomastodon, measuring approximately two metres at the shoulders, had small tusks, two each on the upper and lower jaws and a poorly developed trunk. Paleomastodon as the name implies is "ancient mastodon" because it was a common ancestor of the mastodon and the gomphotheres.