A hand or foot with more than five digits that has a recognizable A/P axis of symmetry. The axis can lie within a normally formed or partially duplicated digit resembling a middle finger, index finger, thumb, toe, or hallux. Alternatively, the axis can be in an interdigital space with a flanking pair of digits that resemble a middle finger, index finger, thumb, toe or hallux. The most lateral digits on each side of the hand/foot typically resemble fifth fingers/toes. [from
HPO]