Functional morphology of the Hippuritidae

Publisher Website
Google Scholar
Abstract
The hippuritid shell consists of a small operculiform left valve capping a larger cylindrico-conical valve. There are 3 shell layers: an outer calcitic fibrillar prismatic layer, a crossed-lamellar aragonitic middle layer and a complex crossed-lamellar aragonitic inner layer. There are also traces of myostracal prismatic aragonite which mark former adductor positions, the attachment site of the body mass, which hung largely from within the left valve, and the pallial curtain of the right valve alone. It seems that water was drawn through the pores on the outer surface of the left valve, into the radial canals which lie within its outer layer. It then flowed outwards from the canal apertures, passing over the broad and radially crenulated right mantle margin, whereon food particles were trapped. The particles were sorted and passed inwards anterio-ventrally onto the ctenidia and/or palps, which carried them to the mouth. Feces were ejected via the dorsalmost of 2 oscules in the left valve, and pseudofeces via the ventralmost oscule. The form of the adductor muscles and their orientations upon myophores projecting from the left valve suggest immovable valves only separated by a minute gape. These modifications complemented the atrophy of the normal bivalve internal feeding and respiratory current system.