The tetrapods are the vertebates which have primitively four limbs. It was long believed that the first tetrapods had five digits. However, the discovery of Ichthyostegaand Acanthostega, to very early tetrapods from the Late Devonian, show that they possessed 7 or 8 digits, and that their limbs were more likely used as special fins to swim in shallow watersfilled with a lot of vegetation, rather than to walk on the land