"Sharks have remained unchanged for 450 million years"
This is a often-heard 'fact', but it simply isn't true. The shark lineage has indeed been around for that long, but they have most certainly changed and evolved in that time.
Another about sharks, but from the Two Oceans Aquariums website
Evolution's ultimate predator: Here are our top 10 prehistoric sharks . It lists Acanthodians, Stethacanthus, Edestus and Helicoprion, none of which are sharks. It also states that Megalodon was primarily a deep sea predator and that the appearance of Orcas caused it to go extinct, both which are untrue.