Eoradiolites liratus (Bivalvia, Radiolitidae) from the Upper Cenomanian Galala Formation at Saint Paul, Eastern Desert (Egypt)

An assemblage of the shallow-water radiolitid Eoradiolites liratus (Conrad, 1852) is described from the Upper Cenomanian Galala Formation at Saint Paul (southern Galala, Eastern Desert, Egypt). At this locality, the stratigraphically youngest rudists occur just below the latest Cenomanian ammonite Vascoceras cauvini/V. rumeaui Biozone. Palaeogeographically, E. liratus shows affinities with southern parts of the Mediterranean Tethyan Realm and a close relationship with the Apulian Plate in particular. The species is restricted to the Cenomanian of the Eastern Desert, whereas in Sinai, as well as in the adjacent eastern Mediterranean and other countries in the Near East, it occurs in older (Albian) deposits. The present collection shows a wide range of variation in shape and ornament, yet this does not involve large differences in individual size. The variation within this assemblage of E. liratus is mainly ecophenotypic, rather than ontogenetic. Bioerosion traces are common in the collection available; the number of borings is high and they are concentrated mainly in the commissural area, in radial bands and interbands as well as in left valves. Such borings indicate a fairly long period of post-mortem exposure for these shells.