The shell structure of the Recent Patellogastropoda (Mollusca: Gastropoda)

Abstract

The shell microstructure of 44 species belonging to 19 genera and 5 families of Patellogas- tropoda was observed by scanning electron microscopy on the basis of material mainly from the Northwest Pacific. As a result, 17 microstructures of prismatic, crossed, and lamellar structures were recognized. The comparison among species revealed 20 shell structure groups which are defined by microstructures and shell layer arrangement. The relations between taxa and shell structural composition indicate that the Recent patellogastropods generally have distinctive and stable shell structures at the genus level. This high level of consistency provides a firm basis for the application of shell structural characters to identify fossil pa- tellogastropods. However, the evolutionary process of microstructures and homology across different shell layers are mostly ambiguous in the absence of robust phylogeny and undoubted positional criteria for comparison. More studies from phylogenetic, ontogenetic and mineralogical viewpoints should be under- taken to discuss the process of shell structure diversification in patellogastropods.