Arsinoitherium was a strange Embrythipod Probiscidean, related closely to the Moeritherium.
It lived in the mangrove deltas and swamps of North Africa, during the Late Eocene Epoch of the Tertiary (Palaeogene) Period, 38-33.5 Ma.
It was a large herbivore, slightly larger than a hippopotamus, and vaguely similar in appearance at a distance (until you see its head)
The most distinctive feature of this strange mammal, are of course the two pairs of horns that adorn the skull. One small pair sit above the eyes, and a far larger and very broad pair of horns, protrude in front of the eyes - and consequently would have created an awkward blind-spot directly in front of its own nose!
Therefore, it would have tilted its head frequently to simply look straight forward. Why this animal evolved such a seemingly awkward ornamentation, is difficult to understand, though the best guess is that it was for mating contests and would have been intimidating to would-be predators and mating rivals. It was probably highly aggressive, exhibiting solitary behaviours. Compared to many animals, it was clearly unintelligent, due to a small brain capacity for its size. It was not alone in this regard; Brontotheres that lived in different habitats in the same time Arsinoitherium did, were twice the size of the largest Rhinos today, but had brains merely 1/3 the size. It gets its name from a very ancient Egyptian Queen, Arsinoe II. Arisinoitherium means, "(Queen) Arsinoe's Beast".