Oldest Record of African Bagridae and Evidence from Catfishes for a Marine Influence in the Late Eocene Birket Qarun Locality 2 (BQ-2), Fayum Depression, Egypt

ABSTRACT

The Birket Qarun Formation, sampling upper Eocene deposits of the Fayum Depression, has been the subject of disagreement in terms of the environmental deposition. The formation has traditionally been considered to be a marine deposit but, more recently, one particular site, Birket Qarun Locality 2 (BQ-2), has been reported to have freshwater vertebrates, indicating that at least this locality in the formation contains terrestrial deposits. We here report a new varied assemblage of fossil catfishes from BQ-2, which adds new information with which to interpret the paleoenvironment of the locality. The new BQ-2 catfish assemblage includes the earliest record of the freshwater family Bagridae in Africa, as well as the oldest records of Fajumia and Socnopaea, otherwise known only from the overlying marine deposits of the Qasr el-Sagha Formation. Notable among the finds are remains of Arius fraasi and two additional species of marine ariid catfishes, representing the first such occurrences from the Fayum deposits. These occurrences indicate that BQ-2 likely had marine influences, or perhaps that Fajumia, Socnopaea, and Arius were euryhaline. In addition, the freshwater families Claroteidae and Mochokidae are represented among our collection. The new material documents the presence of a variety of taxa, and in addition it documents the variation in body size of members of the same family. Most evidence from other vertebrate fossils indicates that BQ-2 is a freshwater deposit, but some elements of the new catfish collection suggest the presence of nearshore marine influences, indicating that a much more complex environment was present.

ACKNOWLEDGMENTS

This research was supported by the Leakey Foundation, Mansoura University, and the U.S. National Science Foundation (BCS–0416164, BCS–0819186, BCS–1231288). Thanks to the Society of Vertebrate Paleontology for the Jackson Student Travel Grant that allowed S.E.S. to present this work at the SVP 77th Annual Meeting in Calgary. We thank the personnel of the Division of Fossil Primates (Duke Lemur Center) for their friendly hospitality and help for the first author (S.E.S.) during the study of this material; G. Gunnell for permission to work on the BQ-2 catfish material, C. Riddle for assistance cataloging the specimens, S. Heritage for CT scanning the specimens, and V. Yarborough for assisting with fossil preparation. We are grateful to MUVP members who helped in the 2017 and 2018 field seasons. Thanks also to the helpful reviews and comments from the editor which improved the manuscript.