Epizoans on late Ordovician brachiopods from Southeastern Indiana

The frequency of epizoans (cornulitids, inarticulate brachiopods, bryozoans, solitary and colonial rugosan corals) on over 8000 specimens of articulate brachiopods (four strophomenids, five orthids, one rhynchonellid) was calculated for four stratigraphic horizons in the Dillsboro Formation of southeastern Indiana. Frequency of shells encrusted correlates significantly with the surface area of the valves. Punctae in brachiopod shells (Onniella meeki) may have deterred larval settlement of epizoans. Coarse ribbing on articulates deterred encrustation by the inarticulate brachiopod. The horn coral shows a preference for attachment to the anterior of Hiscobeccus capax. Bryozoans show a preference for the incurrent lateral margins of inferred living hosts, suggesting rheotropic behavior by settling larvae. Inarticulate brachiopods are concentrated around the sloping commissure of the brachial valve of strophomenids, suggesting geotropic behavior and/or selective survival of settling larvae. Inarticulates deterred overgrowth by bryozoans. High frequencies of encrustations of the medial region of pedicle valves of orthids and strophomenids probably reflect post‐mortem encrustations. Alternating intervals of slow sediment accumulation punctuated by tropical storms and rapid shell burial may account for the high frequency of shells with either their entire surface veneered or only a very small area encrusted by bryozoans.