Sclerobiont assemblages on the late Eocene bivalve Carolia placunoides: Composition, distribution and their paleoecological significance

Here we describe the composition and distribution of sclerobionts on the late Eocene bivalve Carolia placunoides and provide information about its paleoecology. More than 250 shells were collected from the Temple Member of the Qasr El-Sagha Formation exposed in El-Fayum Province. Nine ichnogenera have been recorded including Gastrochaenolites, Maeandropolydora, Caulostrepsis, Entobia, Centrichnus, Belichnus, Anellusichnus, Oichnus and Trypanites. The dense population of borings made by boring bivalves, Gastrochaenolites, is the most remarkable. Encrusters include serpulid worms (Spirobranchus cf. luxata), balanoid barnacles, and oysters. Shells of juvenile Carolia were the most dominant encrusters. Sclerobionts occurred on left and right valves; they apparently favoured the interior surfaces on both valves but they preferred no special sites. The Carolia placunoides shell concentration is interpreted as para-autochthonous assemblage.