Paleontology, paleobiogeography and paleoecology of Carolia-bearing beds from the Late Eocene rocks at Nile-Fayum Divide, Egypt

• The Late Eocene in Nile Fayum Divide is rich with macroinvertebrate fauna.
• Most of the fauna originated in the southern Tethys and spread worldwide.
• The extinction of genus Carolia was a result of biotic and abiotic factors.

The Paleontological study of the Carolia-bearing beds in (Qasr El-Sagha Formation) at Nile-Fayum Divide reveals the presences of thirteen species (three gastropods, six oysters and four Carolias). The paleobiogeography of these fauna indicates that genus Carolia Cantraine, 1838 was first recorded from the Lower Eocene of Egypt and Indian-Pakistani Region and spread out throughout the Tethyan province, West Africa and North and South America and its last occurrence was in the Early Miocene of North America. It shows also that, the first appearance of Ostrea (T.) multicostata (Deshayes, 1832) was in the Paleocene of Tunis and Algeria, and spread during the Eocene into India, northwestern Europe and the entire northern African regions. However, Cubitostrea (Cubitostrea) cubitus (Deshayes, 1832) was first reported in the Middle Eocene of France and spread to Texas in North America and North Africa. The statistical study on genus Carolia indicates that the distance between the byssal muscle scar and the retractor muscle scar increases with the increase of the left valve convexity. The paleoecological study of these faunal groups shows that, the predation and the parasitic elements as well as the stress environmental factors, caused the extinction of genus Carolia at the end of Late Eocene in Egypt.