Discovery of a pleistocene mysticete whale, Georgia Bight (USA)

Abstract

Subfossil evidence, including a nearly complete dentary (∼77%) (left mandible) and two badly eroded vertebrae, of a mysticete whale, were recovered, underwater, from an in situ context, in the Georgia Bight, 30 km offshore St. Catherine’s Island, Georgia. The discovery of the mandible was initially made in 2006 but excavation was not completed until the summer of 2008. Two badly preserved vertebrae were found lying nearby having eroded from the same outcrop as the dentary. The two vertebrae were dated but not analyzed in this report. Direct dating of the subfossils, with the Accelerator Mass Spectometry radiocarbon technique (AMS), using bioapatite, rather than collagen, suggests a common age range for the skeletal materials, 34,000 to 37,000 ka, but it’s speculative to assign these remains to the same animal or, for that matter, the same taxon. The ages determined for the subfossils are in good agreement with the age of the geological deposit, a shell coquina, as previously determined by AMS dating of inclusions and by direct dating of the sediments using Optical Stimulated Luminescence (OSL) dating. Additionally, amino acid raceminization (AAR) ages were obtained for the coquina. Our comparative analysis supports a diagnosis of a dentary of a mysticete whale. Further comparison of preserved morphological characters with those for mysticete mandibles, support a further diagnosis as balaenopterid or eschrichtiid. Coupled with recent, Pleistocene aged discoveries, in Europe, in the North Sea basin, these remains could provide well-dated, new, North American evidence for the extirpated gray whale in the Atlantic basin of the Quaternary.