Bioerosion” was coined by Neumann (1966) as an abbreviation of “biologic erosion”, and describes every form of biologic penetration into hard substrates, i.e., lithic (including skeletal) and woody. An extremely wide range of organisms causes bioerosion (see Bromley, 1970; Warme, 1970, 1975; Ekdale et al., 1984, p. 108–139). The work of these organisms produces trace fossils at all scales, from microscopic to gigantic. Minute scars etched by brachiopod pedicles have a paleoecologic story to tell; at another scale, cliff sapping by communities of boring bivalves and rasping limpets can cause major geographic changes. For example, the work of pholad bivalves played a leading role in the separation of England from the European continent; and had the great armada, sent against England by Philip II of Spain in 1588, not been annihilated by wood-boring shipworms (bivalves), the language of this short-course would have been Spanish.