A species of very large saltwater clam, a marine bivalve mollusk in the family Hiatellidae. It is sometimes known as the mud duck, king clam, or the elephant-trunk clam. Geoducks are one of the longest-living organisms in the Animal Kingdom. They have a life expectancy of about 146 years, with the oldest recorded at over 160 years. Scientists speculate that the geoduck’s longevity is the result of low wear and tear.