Deinotherium was one of the largest animals of the Late Miocene-Middle Pliocene. The length of the body from different species ranged from 3.5–7 metres, and the height at the shoulders reaching 3–5 m (average 3.5–4 m), and weight can be up to 8–10 m. On the surface they resembled modern elephants but the proportions differed from them. Typically, the trunk was relatively hollow, shortened and remained at high, but massive columnar limbs, indicating they are somewhat different than other Proboscidea functions.
The body is rather short on a long tail. Compared with other proboscids, Deinotherium had a rather long and flexible neck, which allowed the structure to lift and bend its head and turn it from side to side. This structure is associated with the ability to lift its head up and make its tusks work. In the normal position of the head, it was positioned horizontally and was in the same place with the neck of the animal. It was potentially one of the biggest proboscids of all time.
Compared with the massive body, the skull of Deinotherium was relatively small, with the characteristic tusks in the lower jaw. Projecting from the jaw of the tusks could reach up to 1 m, but was usually smaller. It is not excluded that the tusks were playing an important role in the social life of these animals, acting, for example, as a tournament of arms of males in the breeding season but were used for getting food. Animals could bend down and break off branches from trees, as well as strip bark from tree trunks for eating. Today it is believed that they inhabited the woodlands and ate soft enough plants (e.g. leaves and fruits).
The deinotheres were the gigantic cousins of the elephants and flourished at the time of Australopithecus. Tusks in the elephant family varied in shape and size as they adapted for different purposes. Wear marks on the downward curved tusks of Deinotherium suggest that they were probably used for stripping tree bark. With such a large increase in lifestyle and the ability to look up high were indispensable. Their food was taken down and brought to the mouth by the trunk; hooked lower tusks in feeding played a complementary role (for example, they helped to bend down and break off branches of trees). In addition, with tusks, animals could sometimes break down bark and soft inner bark. The process of obtaining food was likely related to a significant mobility of the forelimbs, which could allow Deinotherium a wider range of movement than modern elephants. We can assume that their department could seize carpal and turn down branches or small stems.
Deinotherium remains, particularly their tusks and teeth, have been found at the major hominid excavation sites where Australopithecus has also been found, including Hadar, Laetoli, Olduvai Gorge and Lake Turkana.
The "deino" in Deinotherium derives from the same root as the "dino" in dinosaur—this "terrible mammal" (actually a kind of prehistoric elephant) was one of the largest non-dinosaurian animals ever to roam the earth, rivaled only by large mammoths and the rhinoceros Paraceratherium. Apart from its sizable (about 5 to 10 ton) weight, the most notable feature of Deinotherium was its short, downward-curving tusks, so different from the usual elephant appendages that puzzled 19th-century paleontologists reassembled them upside down.
Deinotherium was not directly ancestral to modern-day elephants, instead inhabiting a side branch along with relatives like Amebelodon and Platybelodon. A few species of Deinotherium managed to persist into historical times, until they either succumbed to changing climatic conditions or were either hunted to extinction by early humans. Some experts have speculated that these creatures inspired numerous ancient tales of massive beasts roaming the earth, though Deinotherium was far from the only giant mammal to have inspired our ancient ancestors.