In his off time, he studies the pathology of paleolithic creatures. In other words, he takes great interest in the disease of prehistoric animals. While studying the Platecarpus, a lengthy, aquatic reptile of the mosasaur family, Rothschild and his colleagues discovered an unusual length of dead tissue in otherwise healthy bone. The surprising diagnosis was avascular necrosis. Even more surprising was that after ruling out other causes, they determined that decompression sickness, or the bends, had been responsible.