Deinotheres were relatively conservative and showed little morphological change over their evolution, aside from a progressive increase in body size.

[1] While the earliest deinothere Chilgatherium probably weighed only around 1.5 tonnes (3,300 lb) and was less than 2 metres (6.6 ft) tall, some species of Deinotherium represent among the largest known proboscideans, with shoulder heights of over 4 metres (13 ft) and body masses around 12 tonnes (26,000 lb), considerably exceeding living African bush elephants in body size, making them among the largest land mammals ever.

[3] Phylogeny of Proboscidea showing placement of Deinotheriidae, following Hautier et al. 2021:[3]Eritherium Phosphatherium Daouitherium Numidotherium Barytherium Arcanotherium Omanitherium Saloumia Moeritherium Deinotheriidae Dagbatitherium Palaeomastodon Phiomia Elephantimorpha The oldest known deinothere is Chilgatherium harrisi from the late Oligocene, around 27-28 million years ago.

While these Miocene deinotheres were dispersed widely and evolved to huge elephant sizes, they were not as common as the contemporary (but smaller) Elephantoidea.

Fossil teeth of D. giganteum, from the late-Miocene Sinap Formation at the Turkish site of Kayadibi are larger than those from older localities, such as Eppelsheim, Wissberg, and Montredon, indicating a tendency for increasing size of members of the species over time.

These were the biggest animals of their day, protected from both predators and rival herbivores by virtue of their huge bulk.

D. indicum died out about 7 million years ago, possibly driven to extinction by the same process of climate change that had previously eliminated the even more enormous Paraceratherium.

While in Europe, D. giganteum continued, albeit with dwindling numbers, until the middle Pliocene; the most recent specimen is from Romania.

The causes of the extinction of such a successful and long-lived animal are not known, although a small number of other species of African megafauna also died out at this time.