Host preferences in Late Ordovician (Sandbian) epibenthic bryozoans: Example from the Zahořany Formation of Prague Basin

Abstract

Detailed analysis of the ecologic position of Late Ordovician epibenthic bryozoans within fossil associations from the upper part of the Zahořany Formation have revealed a statistically significant host preference. The most common hosts were found to be cephalopod shells and conulariid exoskeletons, less commonly disarticulated trilobite exoskeletons and brachiopod shells were utilized. Among the trilobite remains, the bryozoans prefered to settle on the central part of cephala in the medium-sized trilobites Dalmanitina socialis. However only one pygidium of more the 450 studied pygidia of the latter species was colonized by epibenthic bryozoans. No preferred area for attachment of bryozoans on brachiopod shells was found. The relation between fluctuating input of clastic material into the mostly siltstone sequence and the occurrence of the epibentic bryozoans is discussed. The changes in the faunal associations of the Zahořany Formation are also documented.