Deinotherium means "terrible beast," which feels a bit unkind to this vegetarian — though he was one of the largest elephants to walk this Earth.
They are relatively recent in the evolutionary story of the Earth. They first appeared 17 million years ago, had a short run of it and became extinct relatively recently — just 1.6 million years ago. This fellow's cousin, Deinotherium bozasi would likely have interacted with some of our oldest relatives.
One of the distinguishing features of Deinotherium is their curved tusks inserted only in the jaw. One of the tusks from this fellow, on display at the Museo Nacional De Ciencias Naturales in Madrid, Spain, while incomplete, was preserved rather nicely and shows the detail of where the tusk meets the jaw. Deinotherium could reach a height of over 3.5 meters. Its structure and size are similar to those of the present-day elephant.