A partial skeleton of the Late Cretaceous lamniform shark,<i>Archaeolamna kopingensis</i>, from the Pierre Shale of western Kansas, U.S.A.

Abstract

ABSTRACT All previous records of the lamniform shark, Archaeolamna kopingensis, are based on isolated teeth. Here we describe a partial skeleton from the Sharon Springs Formation of the Pierre Shale Group of western Kansas, U.S.A. The specimen includes portions of the upper and lower jaws with articulated teeth. The dentition consists of two files of upper and lower anterior teeth that, together with a single file of intrabullar intermediate teeth, are housed in a dental bulla, as well as multiple files of lateral teeth, along with at least two files of lower symphysial teeth and a single file of upper symphysial teeth. The intrabullar intermediate tooth is slightly shorter than the other anterior teeth and has a median cusp with distinctive distal curvature. The dental sequence of A. kopingensis is unique among both extinct and extant lamniforms. Associated with the jaws are fragments of the neurocranium and multiple vertebral centra. A sagittal section through a centrum shows that this shark deposited 18 annual marker bands after its birth and adult size was attained by the 10th band. The robust but penetrating tooth morphology and large jaw circumference suggest that A. kopingensis likely fed upon large prey items. ACKNOWLEDGMENTS We are grateful for the assistance, lab space, and equipment provided by S. A. McLeod and V. Rhue (LACM), M. Everhart (FHSM), H.-P. Schultze, D. Miao, and A. Falk (KUVP), and S. Shelton and D. Pagnac (SDSM). We also extend our gratitude to T. Konishi for discussions on marine reptiles, T. Nomokonova for Russian translation, and M. Templin for French translation. A. Fotheringham (Royal Tyrrell Museum of Palaeontology) developed the protocol for sectioning the centra of LACM 128125. Thoughtful reviews by M. Siverson (Department of Earth and Planetary Sciences, Western Australian Museum, Perth), an anonymous reviewer, and editors J. Maisey and C. Underwood significantly improved the manuscript. Funding for this project was provided by University of Alberta Graduate Student Travel Grant (T.D.C.), Royal Tyrrell Museum Cooperating Society (M.G.N.), and NSERC Discovery Grants A9180 (M.V.H.W.) and 327448 (A.M.M.). Royal Tyrrell Museum Cooperating Society provided two travel grants to M.G.N. Handling editor: Charlie Underwood