This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Ipotane (Greek)
Ipotanes are usually depicted as being half-human half-horse creatures much different from the centaurs. Although sometimes attributed to Greek mythology, the term appears to have originated at a much later date, and without a definite description; they are first mentioned in John de Mandeville's fourteenth-century Travels. Ipotanes appear in modern works of the fantasy genre.
The word "ipotane" appears to be derived from the Greek (hippotes), "a knight", which itself is derived from ????? (hippos), "a horse". Mandeville's description is not clearly distinguishable from that of a centaur, and some depictions use the term synonymously. Some depictions show ipotanes with a human body and a horse's head. Other depictions have them as humans with the hindquarters of a horse.