A deep‐sea burrowing barnacle (Cirripedia: Acrothoracica) form Bermuda

The Acrothoracica constitutes a group of burrowing barnacles limited in distribution to calcareous substrata. Members are found in most warm waters of the world but the greatest diversity is reached in the coralline seas where they are found in coral skeletons, molluscs shells and limestone. Until recently some 37 acrothoracican species were known from the tropical and temperate region, all from waters less than 30 m in depth (Tomlinson, 1969). It was interesting therefore that the first moderately deep water form to become known, occurring at depths between 300 and 650m, should be from cold waters well south of the Antarctic Convergence (Newman & Ross, 1971). This animal, Cryptophialus tomlinsoi, burrows in coral and barnacle shells and does not differ in size and form from littoral members of the genus. The new species described in the present report burrows in foraminifera1 limestone off Bermuda. It is not only remarkable in occurring as deep as 1000 m but in being very much larger and more generalized than any previously known pygophorans. Furthermore it has what is interpreted here as a rostral shell plate, whereas all previously known forms are considered to be without calcereous armament. The existence of what appears to be a rostral plate in the new species has a significant bearing on our understanding of the evolution of the order.