Alestid (Characiformes: Alestidae) fishes from the late Oligocene Nsungwe Formation, Rukwa Rift Basin, of Tanzania

ABSTRACT

Alestidae is a clade of African characiform fishes including 19 extant genera and approximately 105 species that are known from Afro-Arabia, with records reported from the Eocene-Oligocene Jebel Qatrani Formation of Egypt, the Eocene Mahenge crater lake of Tanzania, and early Oligocene to Miocene sites on the Arabian Plate. Here we report the first record of alestid fishes from the late Oligocene Nsungwe Formation in the Rukwa Rift Basin of southwestern Tanzania. The Nsungwe alestid sample is composed of 92 teeth spanning a range of sizes and morphologies. Teeth are examined with regard to cusp number and organization, tooth position and replacement, and in the context of alestid jaw organization using modern, comparative representatives. Results suggest that at least two alestid taxa are represented in Nsungwe Formation localities. Hydrocynus teeth exhibit a single, conical cusp. Several of these specimens preserve a mesiodistally expanded crown and concave surface on the lingual aspect of the tooth. A second, unnamed taxon, with three morphological variants, is distinguished from Hydrocynus based on a multicuspid morphology of fully erupted teeth. The presence of these taxa in the late Oligocene of Africa below the equator provides key insights into the biogeography of the clade.

Citation for this article: Stevens, W. N., K. M. Claeson, and N. J. Stevens. 2016. Alestid (Characiformes: Alestidae) fishes from the late Oligocene Nsungwe Formation, Rukwa Rift Basin, of Tanzania. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1180299.

ACKNOWLEDGMENTS

We thank J. Eastman and J. Duerr for comments on earlier versions of the manuscript, A. Murray for helpful comments on a preliminary presentation, and A. Murray and K. Stewart for helpful reviews of an earlier manuscript draft. S. Egberts, E. Gorscak, K. Melstrom, and K. Whitman prepared specimens, and E. Naylor assisted with graphics. We recognize collaboration with Tanzanian colleagues D. Kamamba, E. Maro, and J. Temu (Antiquities Division). N.J.S. thanks P. O'Connor, E. Roberts, and M. Gottfried for research collaboration in the Rukwa Rift Basin Project. Valuable field assistance was provided by R. Felice, E. Gorscak, H. Hilbert-Wolf, C. Krause, E. Lund, C. Mtelela, E. Naylor, H. O'Brien, J. Sidote, and S. Widlansky. Logistical assistance was provided by H. and M. Faessler. For access to collections, K.C. thanks J. Lundberg, K. Luckenbill, and M. Sabaj-Perez. We thank the American Museum of Natural History and Academy of Natural Sciences of Drexel University for access to specimens used in comparative studies. Funding for this project was provided in part by the Ohio University Undergraduate Research Immersion Program, the Ohio University Center for Ecology and Evolutionary Studies, and the Ohio University Undergraduate Conference Travel Fund. Field and laboratory funding for the project was provided by the National Geographic Society–CRE, LSB Leakey Foundation, Ohio University Research Council, Ohio University Heritage College of Osteopathic Medicine Research and Scholarly Affairs Committee, and the National Science Foundation (EAR 0617561, EAR/IF 0933619, and BCS 1127164).

Submitted November 12, 2015; revisions received February 5, 2016; accepted February 27, 2016.