Occurrence and function of lip hypertrophy in the Anisomyaria (Mollusca, Bivalvia)

Abstract

Examination of the labial structures of 36 species in 24 genera of the Anisomyaria demonstrates that true hypertrophy occurs only in the Pectinidae s.1., Spondylidae, and Limidae. The Propeamussidae lack enlarged lips, evidence supporting their removal from the Pectinidae. Observation of living materials has suggested that rather than serving as a food-retentive hood, the enlarged lips perform a screening function.