The study of several thousand Ordovician (i.e., early Palaeozoic) fossils, mostly trilobites, bivalves, gastropods and echinoderms, demonstrated that most carcasses have become a subject of systematic and sophisticated feeding since the Mid Ordovician. Feeding traces have been preserved as thin tunnels insubstrate inside shells of dead organisms. For a certain period, the substrate had been enriched by microbial consortia; firm fibrous tissues could function as the source of organic matter. Feeding patterns tend to recur for each fossil group; thereby, the positions and shapes of certain non-preserved tissues can be estimated. The above mentioned complex feeding strategies appeared around the GOBE (i.e., Great Ordovician Biodiversification Event) which occurred mainly from 465 to 460 Ma. Paper.