A comparison of molluscan (Bivalvia) phylogenies based on palaeontological and molecular data.

The 18S rRNA gene from three scallop species (Placopecten magellanicus, Chlamys islandica, Argopecten irradians) and 7 mactrid clam species (Spisula solida, S. subtruncata, S. solidissima, Mactromeris polynyma, Tresus nuttallii, T. capax, Mulinia lateralis) have been fully sequenced. Phylogenetic analyses have supported the scheme of Waller (1991) for the Pectinidae but conflict with current evolutionary concepts and classification within the Mactridae. The Mactridae are shown to have evolved monophyletically. The current subfamilial position of Mactromeris, and the subgenera Spisula and Hemimactra of the genus Spisula, are not supported by this data.