NEW IMPLICATIONS ON THE LIFE HABIT OF CYRTINA (BRACHIOPODA, LOWER DEVONIAN)

The Early Devonian Oriskany Formation of Cumberland, Maryland (USA) is characterized by mostly silicified brachiopod shells. Among this brachiopod fauna “Spirifer” intermedius is one of the characteristic brachiopods, represented by medium to large shells with rounded ribs and smooth fold and sulcus. It is usually preserved as articulated shells, however single shells also occur. During the revision of “Spirifer” intermedius, small cyrtinid specimens of Cyrtina rostrata or a closely related species, have been found being attached to the shell of the spiriferid, either on the wings or on the sulcus flanks. For the first time, a fixo-sessile life habit of cyrtinids is reported in which they are fixed with their high and katacline interarea to the shell of “Spirifer” intermedius. Silicification is non-fabric replacive with beekite rings on both the host and the epizoans indicating that silicification preceded decay of the cyrtinid pedicle or that cyrtinids were cemented in juvenile forms. It is interpreted that the cyrtinid brachiopod was using the shell as a hard substrate for pedicle attachment profiting from the inhalant/exhalant current system initiated by the delthyridoid spiriferid.