A POLYPTERID FISH FROM THE CENOMANIAN OF THE BAHARIYA OASIS, EGYPT

Whereas the Cenomanian-aged Bahariya Formation (exposed in the Bahariya Oasis of Egypt) is most famous for its spectacular dinosaur fauna, the unit also preserves a diverse mixture of marine and freshwater fishes. Among the Bahariya Formation freshwater fish is a giant polypterid which is distinct from all other known polypteriform fishes. Scales of the Bahariya polypterid show the isopedine layer characteristic of polypterid scales, but are up to 2cm in length and bear a surface ornamentation of discontinuous ganoin arranged in longitudinal ridges. The Bahariya scales have smaller articular processes than the scales of other polypterids. Similarly large, ornamented scales are otherwise found only in Eocene-aged sediments from the Fayum. Polypterid ectopterygoids bearing a robust processus ectopterygoideus have been recovered from the same levels of the Bahariya Formation as the distinctively ornamented scales. The size and morphology of the ectopterygoid is significantly different from that of Polypterus. The Bahariya polypterid also differs from all other known polypterids in its large size (circa 3m). To date, no polypterid fin spines (which are highly diagnostic for polypterid genera) have been identified in the Bahariya Formation. A lack of knowledge regarding the fin spine morphology of the Bahariya polypterid makes comparisons with other Cenomanian polypterids difficult at this time, but the distinctive scales and unusual ectopterygoid morphology indicate that the Bahariya polypterid should be considered to be generically distinct from Polypterus.