I would have done more but I spent far too much time googling this…

Polydactyly

A baby born with polydactyly has more than five fingers on one hand. An extra finger is often a small piece of soft tissue that can be simply removed. Sometimes, the extra finger contains bones but not joints. Very rarely, the extra finger is a fully functioning digit. A baby may be born with several extra fingers.

There are several different types of polydactyly. Radial polydactyly means there is an extra thumb. Ulnar polydactyly means there is an extra pinky finger. When an extra digit is located in the center of the hand, it is called central polydactyly.

Polydactyly is the most common congenital hand deformity. It affects boys and girls equally. Black children are more likely to have ulnar polydactyly, and Asian and white children are more likely to have radial polydactyly.

Yeah, I got lost for a bit thanks to google.