A high school friend’s older brother was catching some flak from their dad because his chemistry grades weren’t the best. His dad said “I always got As in chemistry.” The retort was “Yeah, but back then there were only four elements.”
Alexander the Great’s horse Bucephalus was polydactyl. Born with vestigial toes. it does happen.
https://theperfecthoof.blogspot.com/2014/11/horse-toes.html