This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Uma-no-ashi (Japanese)
Uma-no-ashi is a legendary beast that is said to be trees which have a horse's legs that dangles from the branches and kicks people who walk by. The horse's leg also hides within the leaves and waits for someone to walk by to kick before returning to hide amongst the foliage. Some Uma-no-ashi are so evil that they'll kick their victim until they are dead.