This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Hippalectryon (Greek)
A hippalectryon or hippalektryon is a type of fantastic hybrid creature of Ancient Greek folklore; half-horse (front) and half-rooster (hind), including the tail, wings and hind legs. Its colour varies between yellow and reddish. The oldest representation currently known dates back to the 9th century BCE, and the motif grows most common in the 6th century, notably in vase painting and sometimes as statues, often shown with a rider.
Aristophanes describes the hippalectryon as a yellow-feathered, awkward-looking creature. The appearance of the creature is consistent amongst the known artistic representations. It involves a horse front part, including the head, withers and the front legs; the hind part is that of a rooster, including the wings, tail and legs.