Lyrodus medilobatus is a shipworm which belongs to the family Teredinidae. Shipworms are marine clams which are highly modified for boring into wood. This species was first described in Hawaii, but its origin is unknown. It has a wide distribution in the Indo-Pacific, from Hawaii and the Galapagos to New Zealand, Australia, and India. In the Atlantic, where we consider it introduced, this shipworm has been collected in Bermuda, the US Virgin Islands, and Florida; however, it is not established in these areas. It is an abundant woodborer in the tropics, found in mangroves and on wood structures.