Giant Land-Dwelling Mammals: Elephants
A distinctive characteristic of elephants (order Proboscidea) is their long snout, or proboscis. During much of the Ceno¬zoic, proboscideans of one kind or another were widespread on the northern continents, but now only two species exist, one in southeast Asia and one in Africa. The earliest member of the order was a 100- to 200-kg creature called Moeritherium from the Eocene that possessed few elephant characteristics. It was probably semi aquatic.

By Oligocene time, elephants showed the trends toward large size and had developed a long proboscis and large tusks, which are enlarged incisors. Most elephants developed tusks in the upper jaw only, but a few had them in both jaws, and one, the deinotheres, had only lower tusks.

The most familiar elephants, other than living ones, are the extinct mastodons and mammoths. Mastodons evolved in Africa, but from Miocene to Pleistocene time they spread over the Northern Hemisphere continents and one genus even reached South America. These large browsing animals died out only a few thousands of years ago. During the Pliocene and Pleistocene, mammoths and living elephants diverged. Most mammoths were no larger than elephants today, but they had the largest tusks of any elephant. In fact, mam¬moth tusks are common enough in Siberia that they have been and continue to be a source of ivory. Until their extinction near the end of the Pleistocene, mammoths lived on all Northern Hemisphere continents as well as in India and Africa.