Ichnology may be defined as the overall study of traces made by organisms, including their description, classification, and interpretation (Simpson, 1975). In a practical sense, however, ichnology is the study of organism- substrate interrelationships (Howard and Frey, 1975). Any given trace is at least a partial record both of the activities of the particular organism and the kind of substrate on or in which it moved. In turn, these activities, as well as local substrate characteristics, may be influenced by contemporary environmental factors. Ichnology thus embraces a complex of processes, conditions, responses, and adaptations, and it draws expertise from...