Barnacle Barnacle A barnacle is a type of arthropod constituting the infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile (nonmotile) suspension feeders, and have two nektonic (active swimming) larval stages. Around 1,220 barnacle species are currently known. The name "Cirripedia" is Latin, meaning "curl-footed". The study of barnacles is called cirripedology. Barnacles are encrusters, attaching themselves permanently to a hard substrate. The most common, "acorn barnacles" (Sessilia), are sessile, growing their shells directly onto the
Whale barnacle sirenians, and crabs–as a group specializing on baleen whales. Turtle barnacles are known from before the Early Tertiary which ended 23 million years ago (mya), and whale barnacles probably diverged in the Late Pliocene 3.5 to 3 mya. "Chelonibia testudinaria" turtle barnacle remains from the Pliocene of Italy seemed to have been associated with right whales ("Balaena" spp.), and could represent a transitional phase; the lack of competing barnacle species and the softer skin compared to the turtle carapace may have led to a divergence and a dispersal. Since whale barnacles are monophyletic, and the family contains a common ancestor