Illustrationg of great white shark jaw with fossil shark teeth, copperplate after Nicolas Steno 1667. Steno produced a book 'Head of a shark dissected' from his dissection of a great white shark caught in the Mediterranean and brought to him in Florence. In it he notes that the 'Glossopetrae' or 'tongue stones' of Pliny are in fact sharks teeth. This was also a conclusion alluded to a century before by Conrad Gesner (see other image in this collection). And Gesner may himself have been led to that conclusion if he read Guillaume Rondelet's 1554 comparison of shark's teeth and tongue stones in his compendium of Mediterranean fishes. Steno however was the first to come up with coherent theories about how such teeth had turned to stone and how they could be found in the ground far from the sea.