The Extra Finger

" Polydactyly or polydactylism (from Greek πολυ- = "many" plus δακτυλος = "finger"), also known as hyperdactyly (plus δακτυλος = "finger"), is the anatomical variant consisting of more than the usual number of digits on the hands and/or feet. It is a congenital abnormality, usually genetically inherited as an autosomal dominant trait. When each hand or foot has six digits, it is sometimes called hexadactyly, or hexadactylism. " via Polydactily

Picture from Wikipedia

" A polydactyl cat is a cat that has more than the usual number of toes on one or all of its paws. In animals including humans, polydactyly (or polydactylism, also known as hyperdactyly) is the anatomical abnormality of having more than the usual number of digits on the hands or feet.

Normal cats have five toes on each front paw and four toes on each hind paw. Polydactyl cats may have as many as seven digits on front and/or hind paws, and various combinations of anywhere from four to seven are common, although each of the front and rear paws are typically the same. Polydactyly is most commonly found on the front paws only, with polydactyly ofall four paws being less common. It is rare for a cat to have polydactyl hind paws only." via cat