The researchers were surprised to find traces of the giant fossil shark's head in the cave walls in Kentucky.
US scientists found a shark as big as a sharp-toothed car that once lived popularly along the Atlantic and Pacific coasts 20 million years ago.
Archaeologists have discovered a species of prehistoric shark not known in a limestone area in Flagstaff, USA.
According to a report on Historical Biology, experts believe that Arizona used to be the home of a community of sharks that is the most diverse of the green planet in the Middle