New ctenacanth sharks (Chondrichthyes; Elasmobranchii; Ctenacanthiformes) from the Middle to Late Mississippian of Kentucky and Alabama

ABSTRACT

Two new ctenacanthiform sharks representing two families, Ctenacanthidae and Heslerodidae, have been identified from the Middle to Late Mississippian marine sediments from Mammoth Cave National Park, Kentucky, and two Late Mississippian marine horizons in northern Alabama. The ctenacanthid, Troglocladodus trimblei, gen. et sp. nov., is known from isolated teeth from the Middle Mississippian St. Louis Formation and Ste. Genevieve Formation of Mammoth Cave and the Late Mississippian Bangor Limestone of northern Alabama. Troglocladodus gen. nov. is characterized by broad median cusps, pronounced longitudinal cristae, multiple intermediate cusps, and labiolingually shortened tooth bases. The heslerodid, Glikmanius careforum sp. nov., is known from isolated teeth and visceral arches from the Middle Mississippian St. Louis Formation and Ste. Genevieve Formation and the Late Mississippian Haney Formation, a Hartselle Sandstone-equivalent shale interval, and Bangor Limestone. Glikmanius careforum sp. nov. has proportionately distinct teeth among species of Glikmanius, with more robust and shorter cusps. The palatoquadrate of G. careforum has a short palatine ramus, otic process that is dorsoventrally deep and less expanded antero-posteriorly similar to Heslerodus and Dracopristis, and an elongated quadrate process like Heslerodus. The Meckel’s cartilage is less dorsoventrally deep than Dracopristis. These two new ctenacanth taxa add important information on the diversity of Ctenacanthiformes suggesting three major lineages within the order. Ctenacanths have a rich fossil history from the Late Devonian to the Middle Permian evolving a variety of tooth types and small to large body sizes.

ACKNOWLEDGMENTS

We are greatly indebted to Mammoth Cave National Park (MACA) Superintendent Barclay Trimble and head of the MACA Science and Resource Management unit, Timothy Pinion, for their support of our paleontological resource inventory and research into the Mississippian fish assemblages. The success of our Mammoth Cave PRI project is largely in part due to a dedicated group of staff and volunteers who have helped us document new fossil localities and spot new fossils within the passages of Mammoth Cave. Park guide Rich Boldon has been instrumental in the discovery of a number of new fossil localities for this project. We also thank our fossil “spotters” K. Alessi, B. Belanger, K. Bobo, M. Cecil, M. Cleveland, J. Douglas, A. Flowers, C. Groves, M. Harris, J. Honaker, E. Jakaitis, P. Kambesis, N. Leies, M. May, K. Mikowski, M. Schorr, S. South, B. Trimble, and E. Winkler. We would like to thank A. Klompmaker of the Alabama Museum of Natural History Paleontology Collections for allowing us to reposit and study this material. We thank R. Keyes for his insights on the lithology and depositional environment of Cedar Creek Reservoir. We would also like to thank the Birmingham Paleontological Society (BPS) for their support throughout the project. Special thanks to D. Elliott for reviewing an earlier draft of the manuscript.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

AUTHOR CONTRIBUTIONS

JPH, RT, CE, JST, and VLS designed the project, JPH drafted the manuscript, JPH, RT, CE, GW, JRW, RO, and KT gathered data, and JPH analyzed the data. All authors edited the manuscript.