Abstract: Invertebrate trace fossils are usually considered as stratigraphically less useful than vertebrate footprints. This is because they commonly lack diagnostic “fingerprints”, which are more closely related to the anatomy of the producer than to the biological purpose, or function, of the trace. Exceptions are trilobite burrows (Cruziana) , arthrophycid burrows, ichnospecies of Oldhamia, and Treptichnus pedum. Even if their makers are unknown, they represent taxonomically coherent groups of animals, whose evolving behavior marks geologic time. Cruziana ichnospecies can also be used in paleogeography.

Abstract For environmental interpretation, biogenic sedimentary structures have the obvious advantage that they are absolutely autochthonous (rare exceptions can be easily recognized) and that they reflect a direct behavioral response to environmental conditions. On the other hand, the palichnological record is largely biased by preservational factors. The majority of the biogenic traces that we observe in present-day environments, particularly the exichnial ones--those on the upper surface of a bed (Martinsson, 1970; Chapter 1 , Table 2) -- may have an almost zero fossilization potential. We, therefore, consider the study of modern traces as a prerequisite to understanding the origin of individual trace fossils, but our paleoenvironmental classification is based mainly on comparisons between fossil ichnocoenoses; i.e., on the other side of the “f ossilizati barrier”.