Taphonomic inferences on boring habit in the richmondian Onniella meeki epibole

Shell boring is one of the few quantifiable, well-preserved biotic interact ions in the fossil record. While some workers have used boring intensity as a proxy for predation pressure in, both Recent and fossil assemblages, oth ers have warned that taphonomic and other effects can alter the boring inte nsity and lead to paleoecological misinterpretation. When the biocoenosis i s known, however, taphonomic effects can be "undone" a posteriori. Because the valve ratio of any bivalved organism must be 1:1 in, the biocoenosis, s trengths of between-valve taphonomic biases can be calculated directly for any disarticulated assemblage of bivalved fossils. By back-calculating the biocoenotic boring intensities, improved estimates of boring stereotypy may be obtained. These "restored" boring intensities can provide more accurate paleoecological interpretations of boring- habit while remaining numerical ly conservative. Taphonomic analysis of a bored Ordovician brachiopod assemblage shows that (li the assemblage had experienced negligible differential transport; and ( 2) convex (pedicle) valves have been preferentially crushed in place. Compa ring the taphonomy of the assemblage to a set of laboratory taphonomic regi mes reveals that valve-valve contact may be of great consequence in skeleta l taphonomy. In particular, valve-valve contacts appear to promote (1) pref erential destruction of convex valves; and (2) subequal destruction of bore d vs. unbored valves. Taking into account these taphonomic effects, numerou s hypotheses of boring habit-including mixed-motive boring-have been tested using a probabilistic model. The model herein presented indicates a likely contribution of 10-15% predatory boring in the assemblage. The usefulness of probabilistic models for providing simultaneous, realistic tests of mult iple hypotheses is emphasized.