The very first members of the elephant order arose in Africa, and remained there exclusively during the Paleocene and Eocene epochs. The oldest known example is from fragmentary remains found in 1996 from the Paleocene of Morocco. These ancient proboscids, such as Numidotherium, are poorly preserved, but resemble the better preserved Moeritherium which arose later in the upper Eocene in Egypt.

Charles William Andrews described Moeritherium and suggested that it was an amphibious creature that lived in swamps or shorelines. The skeleton is of a small pig-like animal with short limbs and a barrel-like body. There is no evidence of a trunk, though some authors and illustrators depict Moeritherium with a prehensile snout like a tapir.

The dentition of modern elephants differs widely from the ancient Moeritherium, and presumably other ancient proboscids as well. Moeritherium has multiple pairs of molars and premolars, unlike modern elephants. While the second incisors of Moeritherium are greatly enlarged, it does not possess tusks and it retains canines on the upper jaw, separated from the cheek teeth by a gap known as a diastema.

Despite the resemblance of Moeritherium to the earliest proboscideans, they are not thought to be ancestral to modern elephants, rather a relict clade of the order that died out and left no descendants. Moeritherium does share some characteristics with the aquatic desmostylians, which evolved later in the Oligocene epoch. The precise relationship between the desmostylians and the proboscids is unclear.

Deinotheriidae

The Deinotheriidae, or Deinotheres, were elephant-like in size and body proportion, but are thought to have diverged from the rest of the proboscidean order some time earlier than other families. They lived from the Oligocene and died out fairly recently in the Pleistocene, living throughout Europe, Africa and Asia. The family was described in 1845 by Charles Lucien Bonaparte.

Deinotherium, described in 1825 by Johann Kaup, is known from fossil remains dating from the Miocene to the Pleistocene. At over four meters tall at the shoulder, it was one of the largest land mammals that has ever existed.

Deinotherium expressed a primitive dentition with multiple pairs of molar and premolar teeth. Upper incisors and canines were completely lost, but the lower incisors became greatly enlarged and curved downwards from the lower jaw, reminiscent of the tusks of modern elephants.

A primitive Deinothere, Chilgatherium from the late Oligocene of Ethiopia was described William Sanders in 2004. Smaller than later Deinotheres and known from only a few distinctive teeth, it is not known if the lower incisors had become as tusk-like as those observed in Deinotherium.

Reference:

• Gheerbrant, E., Sudre, J. & Cappetta, H. A. Palaeocene Proboscidean from Morocco. Nature 383: 68-70 (1996)

• Kappelman, J., Rasmussen, D.T., Sanders, W.J., Feseha, M., Brown, T., Copeland, P., Crabaugh, J., Fleagle, J., Glantz, M., Gordon, A., Jacobs, B., Maga, M., Muldoon, K., Pan, A., Pyne, L., Richmond, B., Ryan, T., Selffert, E.R., Sen, S., Todd, L., Wiemann, M.C. & Winkler, A. Oligocene mammals from Ethiopia and faunal exchange between Afro-Arabia and Eurasia. Nature 426: 549-552 (2003)

• Osborn, H.F. The Feeding Habits of Moeritherium and Palaeomastodon. Nature 81: 139-140 (1909)

• Sanders, W.J., Kappelman, J. & Rasmussen, D. T., (2004), New large-bodied mammals from the late Oligocene site of Chilga, Ethiopia. Acta Palaeontologica Polonica Vol. 49, no.3, pp. 365-392. Paleobiology 30: 146-161 (2004)

• http://paleodb.org/cgi-bin/bridge.pl