The titan acorn barnacle (Megabalanus coccopoma) is a species of large barnacle in the family Balanidae. It lives on Pacific coasts of Central and South America, although it occurs as an invasive species in other parts of the world due to fouling from ships. Growing up to two inches in both height and width, it is one of the larger barnacles. Fossils belonging to this species are known from the Pliocene, between 5.3 and 2.6 million years ago, during which time the barnacle lived as far north as Baja California; however, this area was farther south at the time due to continental drift.
