PASSAMANECK, Y.J.*; HALANYCH, K.M.: Molluscan phylogenetics inferred from 28S rDNA and 18S rDNA sequences.

The Mollusca are recognized as one of the most diverse and specious of metazoan phyla. The relationships between the major groups within this clade have been a subject of ongoing debate. In particular, the origins of aplachophorans and polyplachophorans, which are believed to be basal lineages, have been variously interpreted based on morphological and developmental characters. To date higher level molluscan evolution has received limited attention from the standpoint of molecular phylogenetics. The present study incorporates sequences of both 28S rDNA and 18S rDNA, collected from a variety of molluscs. The two datasets are analyzed separately and together to access the amount of phylogenetic signal in these molecules. Broad taxonomic sampling of both genes allows new insights into the evolution of this major clade of protostome metazoans. These results are assessed in light of traditional hypotheses of molluscan evolution.