Sharks don’t fossilize well because they’re from the class of chondrichthyes meaning their skeletons are made of cartilage, a flexible connective tissue. This is one of the reasons why there is a disagreement over when the first shark first existed. However, shark teeth do fossilize well and sharks produce thousands of teeth in a lifetime. The oldest shark teeth date back to the Devonian Period about 400 million years ago and were found in Europe. Shark scales also fossilize well. Paleontologists can discover many important things from fossilized shark teeth and scales even though it doesn’t seem like much. Their discoveries include information about species, size and behavior. While it is controversial, some paleontologists believe that the first scales are from the Ordovician Period 455 million years ago. Nonetheless, the scales found in Siberia and Mongolia during the SIlurian Period 420 million years ago are definitely from sharks.
More complete fossilized shark remains are more recent dating back to 380 million years ago. They included fossilized shark brain cases.
Sharks have survived all 5 mass extinctions the ordovician-silurian mass extinction, the late devonian mass extinction,the permian mass extinction,the triassic jurassic mass extinction, and the cretaceous-tertiary mass extinction. All of the mass extinctions resulted in a change in the environment. The worst mass extinction was 251 million years ago and 95% of species were killed from…