Syndactyly (from Greek συν- = "together" plus δακτυλος = "finger") is a condition where two or more digits are fused together.
Polydactyly in early tetrapod aquatic animals, such as in Acanthostega gunnari (Jarvik 1952), one of an increasing number of genera of stem-tetrapods known from the Upper Devonian, which are providing insights into the appearance of tetrapods and the origin of limbs with digits.