Behemoth in Wikipedia
Behemoth, is generally translated by "great beasts"; in its wider signification it includes all mammals living on earth, but in the stricter sense is applied to domesticated quadrupeds at large. However in Job, xl, 10, where it is left untranslated and considered as a proper name, it indicates a particular animal. The description of this animal has long puzzled the commentators. Many of them now admit that it represents the hippopotamus, some Young Earth Creationists think it's a dinosaur like the Apatosaurus or the Brachiosaurus, so well known to the ancient Egyptians; it might possibly correspond as well to the rhinoceros.