Ypotamis
The Ypotamis is a creature from Medieval myth made from distorted accounts of hippopotami. They’re amphibious creatures that hunt humans for food. They are typically described as hybrids of horse and human.
Citations:
Barber, Richard, and Riches, Anne. A Dictionary of Fabulous Beasts. United Kingdom, Boydell Press, 1996.
Rose, Carol. Giants Monsters and Dragons: An Encyclopedia Of Folklore Legend And Myth. United Kingdom, WW Norton, 2001.