Evolution of starfishes: Morphology, molecules, development, and paleobiology. Introduction to the symposium

SYNOPSIS. Among starfishes, fascinating life cycles and complex morphological patterns have evolved within a familiar but unusual basic body plan. In spite of these rich complexities, available phylogenetic interpretations conflict, and the history of this important group remains uncertain. The symposium brought together current perspectives on phytogeny, the implications of certain poorly known aspects of asteroid morphology, and consideration of significant events that preceded the diversification of extant asteroid groups in the Mesozoic. It has become axiomatic in modern organismal biology that strongly supported phylogenetic reconstructions are crucial to the understanding of biological pattern and progress. Although asteroids exhibit complex morphologies, life cycles, and behaviors that indicate their status as ideal model organisms in the study of marine invertebrates, their evolutionary history remains obscure. This is in part due to a lack of treatment by researchers but also in part due to inherent limitations of the available data. In the following pages, the state of inquiry into the study of relationships among starfishes is arranged in three sections: the nature of the fossil record (an introduction to modern starfishes), taxa and morphology, and phylogenetic interpretations.