Researchers from Pennsylvania State University have found that the scales of an extinct ancient fish could lead to the first teeth to appear in animals. Article published Journal of Anatomy.
Paleontologists studied the fossil of the species. ischyrhiza mira – An extinct sawfish that lived in North America between 65 and 100 million years ago. Like modern saw sharks, this creature had serrated spines around its snout to deter predators and foraging. These spines are thought to be modified versions of the scales on the rest of the body. The scientists who studied them did not intend to study the evolutionary history of the appearance of the teeth, but it turned out that the upper scale layer is similar in structure to the enamel of a shark tooth.
The scales were much more complex than normal and consisted of fluoropatite microcrystalline bundles arranged in more randomly arranged smooth lines near and below the tooth surface. Packed microcrystals placed perpendicular to the tooth surface pass through these layers. This combination of different crystal directions gives the shark tooth a special strength.
It is possible for scales and teeth to develop a similar structure in parallel, but it is more likely that our teeth are actually highly developed fish scales.