Rocks and Fossils 7: shark What's this? Expand This is a fossil tooth of a prehistoric oxyrhina shark that lived in the seas that covered Kent in the Cretaceous period (145 to 65 million years ago). Sharks were fierce predators feeding on fish and other marine life. Their mouths were filled with rows of razor-sharp teeth that tore their victims to shreds. What part of a prehistoric shark are these? Expand These are fossil vertebrae from the backbone of a prehistoric shark. It lived in the Great Chalk Sea that covered Kent in the Cretaceous, at the time of the dinosaurs. Did you know? The largest prehistoric shark Megalodon was longer than a bus, the weight of 10 elephants and had teeth up to 20cm long! It feasted on prehistoric whales, dolphins, squid and even giant turtles.