SABIA ON SHELLS - A SPECIALIZED PACIFIC-TYPE COMMENSALISM IN THE CARIBBEAN NEOGENE

In the Recent biota, species of the hipponicid gastropod genus Sabia t hat excavate characteristic pits on the outer surfaces of shells of re ef-dwelling gastropods and hermit crabs occur only in the tropical Ind o-West Pacific region and in adjacent warm-temperate parts of Japan an d Australia. I report the discovery of Sabia pits in reef-associated g astropod shells from the Cercado (late Miocene) and Gurabo (early Plio cene) Formations of the Dominican Republic. The likely culprit was Hip ponix otiosa Pilsbry and Johnson, 1917, a species here reassigned to S abia Gray, 1840. Pliocene extinction, which was far more severe in the Caribbean and elsewhere in the western Atlantic than in the Indo-West Pacific, selectively eliminated Sabin and its commensalism from Atlan tic reef ecosystems. This case is one of several examples indicating t he vulnerability of specialized associations to extinction-causing dis turbances.