Hippogryph: part horse, part lion, part eagle. First described in a poem in the 16th century, it was said to have been born from the union of a mare and a gryphon. Commonly depicted in medieval heraldry, it is symbolized to represent love, as gryphons and horses were mortal enemies.
Keep in mind that one of the natural dangers of Equestria is a flying snake-chicken who can turn you to stone with a look. Biology and genetics there are weird.