An inventory of belemnites documented in six US National Parks in Alaska

Schraer, Cynthia; Schraer, David; Tweet, Justin; Blodgett, Robert; Santucci, Vincent

Belemnites (order Belemnitida) are an extinct group of coleoid cephalopods, known from the Jurassic and Cretaceous periods. We compiled detailed information on 252 occurrences of belemnites in six National Park Service (NPS) areas in Alaska. This information was based on published literature and maps, unpublished U.S. Geological Survey internal fossil reports ("Examination and Report on Referred Fossils" or E&Rs), the U.S. Geological Survey Mesozoic locality register, the Alaska Paleontological Database, the NPS Paleontology Archives and our own records of belemnites found in museum collections. Few specimens have been identified and many consist of fragments. However, even these suboptimal specimens provide evidence that belemnites are present in given formations and provide direction for future research. Two especially interesting avenues for research concern the time range of belemnites in Alaska. Belemnites are known to have originated in what is now Europe in the Early Jurassic Hettangian and to have a well-documented world-wide distribution in the Early Jurassic Toarcian. Some researchers (Iba et al. 2011) suggest that belemnites were absent from the North Pacific after the Early Cretaceous. We found several claims of belemnites prior to the Toarcian and in the Late Cretaceous. However, there were potential limitations in the data. These findings indicate a strong need for further collecting and detailed study of the specimens to assure that the Sinemurian-age belemnites are truly belemnites rather than aulacocerids, a morphologically similar taxon with earlier origins. Reassessment of the age of the strata in which possible Early Jurassic and Late Cretaceous belemnites are found is crucial. Further studies could shed light on the evolution and migration patterns of belemnites, and on the motion of terranes that make up Alaska.