It is usually assumed that Herodotus copied his description of the hippopotamus from the Description of the earth by Hecataeus of Miletus. Probably, neither Hecataeus nor Herodotus ever saw a hippo, which was extinct in Egypt by the time they visited the ancient country along the Nile.
Representing the hippopotamus was something that appears to have been impossible in Antiquity; the description by the author of Job 40.10 (or 40.15) is not very accurate too (cf. the animal on the this mosaic of the Villa Nile near Lepcis Magna).
[2.73] The hippopotamus is held sacred in the district of Papremis, but not elsewhere. This animal has four legs, cloven hoofs like an ox, a snub nose, a horse's mane and tail, conspicuous tusks, a voice like a horse's neigh, and is about the size of a very large ox. Its hide is so thick and though that when dried it can be made into spear-shafts.