Deinotherium

Deinotherium ("terrible beast" derived from the Ancient Greek δεινός, deinos meaning "terrible" and θηρίον, therion meaning "beast") was a large prehistoric relative of modern-day elephants that appeared in the Middle Miocene and survived until the Early Pleistocene. During that time it changed very little. In life, it probably resembled modern elephants, except that its trunk was shorter, and it had downward curving tusks attached to the lower jaw.



Taxonomy and evolution
Deinotherium is the type genus of the family Deinotheriidae, which evolved from the smaller, early Miocene Prodeinotherium. These proboscideans represent a totally distinct line of evolutionary descent to that of other elephants, one that probably diverged very early in the history of the group as a whole. The large group to which elephants belong formerly contained several other related groups: besides the deinotheres, there were the gomphotheres (some of which had shovel-like lower front teeth), and the mastodons. Only elephants survive today.

Three species are recognized, all of great size. Deinotherium giganteum is the type species, and is described above. It is primarily a late Miocene species, most common in Europe, and is the only species known from the circum-Mediterranean. Its last reported occurrence is from the middle Pliocene of Romania (2 to 4 million BP). An entire skull, found in the Lower Pliocene beds of Eppelsheim, Hesse-Darmstadt in 1836, was 4 ft (1.2 m) long and 3 ft (.9 meters) wide, indicating an animal exceeding modern elephants in size. Deinotherium indicum is the Asian species, known from India and Pakistan. It is distinguished by a more robust dentition and p4-m3 intravalley tubercles. D. indicum appears in the middle Miocene, and is most common in the late Miocene. It disappeared from the fossil record about 7 million years BP (late Miocene). Deinotherium bozasi is the African species. It is characterized by a narrower rostral trough, a smaller but higher nasal aperture, a higher and narrower cranium, and a shorter mandibular symphysis than the other two species. D. bozasi appears at the beginning of the late Miocene, and continues there after the other two species have died out elsewhere. The youngest fossils are from the Kanjera Formation, Kenya, about a million years old (early Pleistocene).

Description
Permanent tooth formula of D. giganteus is 0-0-2-3/1-0-2-3 (deciduous 0-0-3/1-0-3), with vertical cheek tooth replacement. Two sets of bilophodont and trilophodont teeth. Molars and rear premolars tapiroid, vertical shearing teeth, and show that deinotheres became an independent evolutionary branch very early on; other premolars used for crushing. The cranium is short, low, and flattened on the top (in contrast to more advanced proboscids, which have a higher and more domed forehead; the implication may be that deinotheres were less intelligent than other proboscids), with very large, elevated occipital condyles. The nasal opening is retracted and large, indicating a large trunk. The rostrum is long and the rostral fossa broad. Mandibular symphyses (the lower jaw-bone) is very long and curved downward, which, with the backward curved tusks, is a distinguishing feature of the group; it possessed no upper tusks.

Deinotherium is distinguished from its predecessor Prodeinotherium by its much greater size, greater crown dimensions, and reduced development of posterior cingula ornamentation in the second and third molar.