Studies of larval development in the calyptraeid gastropod genus Crepidula Lamarck, 1799 have greatly enhanced the ability of systematists to delineate the Recent species in this challenging group. Although the simple, limpetlike growth form and near absence of surface ornamentation in adult Crepidula provide few diagnostic characters, larval developmental strategies (i.e., feeding or planktotrophic vs. nonfeeding or lecithotrophic larvae) appear to be stable within species and evolve rapidly, making them useful taxonomic tools. Molecular phylogenetic analyses of several species previously believed to possess multiple developmental modes—a condition known as poecilogony—found that these “species” are instead clades comprised of multiple cryptic species distinguishable only by larval type (e.g., Gallardo, 1977, 1979; Hoagland, 1977, 1984, 1986; Collin, 2000a, 2001).