PALEOECOLOGY OF A TROPICAL LATE CRETACEOUS (CENOMANIAN) SKELETOZOAN COMMUNITY IN THE NEGEV DESERT OF SOUTHERN ISRAEL

Cretaceous tropical hard substrate communities are not well known, so the Mesozoic carbonates of the Middle East provide numerous opportunities to fill in paleobiogeographical and paleoecological gaps. One such unit is the En Yorqe’am Formation exposed in Hamkhtesh Hagadol, Hatira anticline in the Negev desert of southern Israel. It is a fossiliferous argillaceous limestone and marl about 60 meters thick in this location. The oyster Ilymatogyra (Afrogyra) africana (Lamarck, 1801) is abundant near the middle of the formation. The thick shells of I. africana provided pre- and post-mortem substrates for a diverse encrusting and boring community. The common encrusters include ostreid and spondylid bivalves, the cyclostome bryozoan Stomatopora, and the agglutinating foraminiferan Acruliammina. Bioerosion structures include Tiers B, C, D, and E of Bromley & Asgaard (1993). The shallowest is represented by the echinoid rasping Gnathichnus pentax, which was almost certainly produced by Heterodiadema lybicum. The acrothoracican barnacle boring Rogerella elliptica is next deepest; some of these are found in aligned aggregations rather similar to the enigmatic Feldmannia. Entobia aff. E. megastoma, a non-camerate excavation produced by a clionid sponge, is the deepest boring. Many of these skeletozoans are described for the first time from the tropical Cretaceous. The I. africana oyster bank that they inhabited was formed during a general transgression in the Cenomanian. The oysters and their skeletozoans show normal marine conditions in this portion of the platform.