Scientists have found ancient nail tooth shark fossils deep inside Mammoth Cave in Kentucky, revealing new information about a mysterious group of extinct predators.

Fieser, L. F., and Fieser, M., Natural Products Related to Phenanthrene (third ed.), 204 (Reinhold, New York, 1949). Fieser, L. F., and Fieser, M., Steroids, 177 ...