340-million-year-old 'nailtooth' shark discovered deep in Kentucky's Mammoth Cave

A McGinnis's nailbill (Clavusodens mcginnisi) is pictured hunting for a crustacean in a reef-like forest of crinoids during the Carboniferous period. (Image credit: NPS Illustration/Benji Paysnoe) Scientists examining fossils deep within Kentucky's Mammoth Cave have stumbled upon the remains of…