EPIBIONTS ON DECAPOD CRUSTACEA AS SOURCES OF PALEOECOLOGICAL AND TAPHONOMIC INFORMATION

Epibionts on fossil decapod Crustacea offer the potential for enhancing interpretations of paleoecology and taphonomic history of the fossils. To determine the significance of the epibionts in these studies, it is essential to be able to determine whether the organisms attached to the decapods while the host was alive or whether the attachment was post-mortem. Paleoecological conclusions can only be made using information from organisms demonstrably associated during life. Orientation and position of epibionts suggesting that they were situated to derive benefit from current flow or concealment document a living association. Waugh et al. (2003) demonstrated that the potential for preservation of living associations is biased by many factors including epibiont loss due to exfoliation of the epicuticular layer of the decapod carapace both during life of the decapod and rapidly following molting or death. It is this layer to which the epibionts attach. Thus, presence of epibionts on articulated decapod corpses, suggesting life association, is possible only if the decapod is preserved as a result of extremely rapid burial. Taphonomic conclusions may be drawn from epibionts attached to decapod skeletal material on various surfaces and in unpredictable orientations, suggesting that the host decapod was dead prior to infestation. Studies in progress by Jakobsen et al. document heavy epibiont infestation on carapaces of Paleocene decapods from Denmark. These carapaces were interpreted to be molts because the interiors and exteriors of carapaces served as a site of infestation. These remains were exposed on the seafloor long enough to suffer significant epibiont growth. Thus, the most frequent occurrences of epibionts observed on fossil decapods to date are on molts or corpses of organisms that are exposed long enough to provide a hard substrate but are not destroyed by the rapid scavenging to which decapod remains are subject.