A GIANT LUCINID BIVALVE FROM THE EOCENE OF JAMAICA - SYSTEMATICS, LIFE HABITS AND CHEMOSYMBIOSIS (MOLLUSCA: BIVALVIA: LUCINIDAE)

The giant bivalve Lucina megameris Dall, 1901, from the late Eocene White Limestone Group of Jamaica and by far the largest known species of the family Lucinidae, is placed in a new genus Superlucina. Apart from its large size, with a shell height exceeding 310 mm, it is distinguished from other genera, such as Pseudomiltha and Eomiltha by external shell characters and the extremely long and narrow, anterior adductor muscle scar. Features preserved on internal moulds suggest that, in common with living Lucinidae, S. megameris was chemosymbiotic with sulphide - oxidizing bacteria housed in the gills. Palaeoenvironmental evidence suggests a habitat in oligotrophic, shallow waters, probably in seagrass beds, with an associated molluscan fauna includ- ing large cardiids that may have been photosymbiotic. Super- lucina is considerably larger than any living lucinid that range in size from 3 to 150 mm with most encompassed within 5-30 mm. From the Jurassic onwards, a few other large lucinids are known from cold seep sites, with several other records from possible shallow water seagrass beds.