Paleoecology and evolutionary significance of hard substrate trace fossils

Trace fossils produced in hard substrates, such as rock, shells, bone and wood, are formed either by destructive bioerosion or constructive embedment. The high resolution preservation of these fossils and their amenability to being linked to biotaxa make them well suited for paleoecological and evolutionary studies, and based on these merits the new subdiscipline, lithichnology is recognized.; Bioclaustration cavities, which form when one animal embeds in the growing skeleton of another animal, are recognized as direct evidence of ancient symbiosis. A review of Paleozoic bioclaustrations shows a diversity increase during the Late Ordovician, reaching a climax by the late Middle Devonian, and a collapse during the Late Devonian leading up to the Frasnian-Famennian mass extinction episode.; The oldest known Helicosalpinx asturiana, a spiral bioclaustration, is preserved in Columnopora and Calapoecia (tabulate corals) from Ontario. The unaffected growth of host coral suggests that the symbiont was a commensal. This coral-symbiont association is the earliest known globally significant fossil evidence of intermetazoan symbiosis.; Endolithic trace fossils are part of a reef ecosystem that developed following the Late Devonian Alamo Bolide Impact Event in Nevada. A new bioclaustration, Chaetosalpinx isp. A, occurs in clusters within reef-building stromatoporoids. The dominant boring in Nevada is similar to Topsentopsis devonica Clarke, a camerate boring that is suggested here to be a junior synonym of Entobia Bronn.; Bivalve borings (Gastrochaenolites) are described for the first time in coprolites and bone from Cretaceous-Eocene phosphatic conglomerates in Mali. The bored coprolites indicate rapid lithification of the ancient fecal matter and point to early diagenetic phosphogenesis of the clasts.; A new microboring, Rosette A, is described from Ordovician-Silurian brachiopod shells from Anticosti using SEM and CT scanning. Interpretation of the depositional setting suggests that the microborings were produced in quiet water, below normal storm wave base but within the photic zone.; The guild concept is suggested as an ecological framework to organize hard substrate trace fossils. Differences in the evolutionary trends among the polyphyletic guilds points to extrinsic controls, such as competition and predation, as primary driving forces in the exploitation of the endolithic habitat by organisms.