BIOEROSIVE STRUCTURES OF SCLEROZOAN FORAMINIFERA FROM THE LOWER PLIOCENE OF SOUTHERN SPAIN: A CONTRIBUTION TO THE PALAEOECOLOGY OF MARINE HARD SUBSTRATE COMMUNITIES

Abstract:  A palaeoecological study of sclerozoan foraminifera of the families Saccamminidae (aff. Sagenina ), Lituolidae ( Placopsilina ), Cibicididae ( Cibicides , Dyocibicides , Cibicidella ) and Planorbulinidae ( Planorbulina and Planorbulinella ) that colonized epifaunal bivalves (ostreids and pectinids) during the early Pliocene in southern Spain has led to the recognition of two new boring ichnogenera: Camarichnus ichnogen. nov., with two ichnospecies, C .  subrectangularis ichnosp. nov. and C .  arcuatus ichnosp. nov., and Canalichnus ichnogen. nov., with one ichnospecies, C .  tenuis ichnosp. nov. The first two ichnospecies were produced by adnate lituolids and cibicidids, the last by saccamminids. Their recognition is very important when quantifying populations of these organisms. Colonisation took place after death of the host bivalves, when they acted as very stable substrates whose topography probably controlled the initial settlement pattern of the foraminifera. The colonisation sequence started with the foraminifera (lituolids-saccamminids-cibicidids-planorbulinids) and was followed by vermetid gastropods, serpulids, spirorbids, cheilostome bryozoans and/or ostreids. Preferred orientations and overgrowth relationships between cheilostome bryozoans and serpulids have been detected in this material.