Parasitism of Paleozoic Crinoids and Related Stalked Echinoderms: Paleopathology, Ichnology, Coevolution, and Evolutionary Paleoecology

Stalked echinoderms (pelmatozoans) are an excellent group for studying parasite-host relationships in deep time and for tracing the long-term evolutionary effects of such biotic interactions through geologic history. This is due largely to the unique nature of the echinoderm calcitic endoskeleton, which is both (1) chemically stable, facilitating ready preservation, and (2) capable of being modified during the life span of the individual in response to infestation. The two most common forms of evidence for parasitism of pelmatozoans are shallow pits, often associated with swelling and development of galls, and platyceratid gastropods, sometimes directly overlying borings. Pits are found in Paleozoic representatives of four pelmatozoan classes and show strong host specificity, persistent over geologically significant time intervals. Platyceratid gastropods, found on three pelmatozoan classes, are sometimes found immediately over borings or in positions allowing access to gonads and/or undigested food in the stomach. The presence of parasites appears to have induced significant morphological changes in host lineages