Animal Planet produced a special called "The Future Is Wild" which was supposedly written with the help of evolutionary scientists, though i'd sure like to know what barrel-botom they scraped these guys off of. It was supposed to show how species would evolve here on Earth over the next few million years, but some of the conclusions were beyond ludicrous. For example, any evolutionaist will tell you sharks have been virtually unchanged for about 300 million years, but on this show they suddenly developed a sophisticated social culture like dolphins, changed the type of prey they hunted and became pack hunters, and evolved a communications system that flashed messages via bioluminescent panels on their skin. They never felt a need to explain what sort of evolutionary pressure would lead to changes that radical.
Yeah, riiiiight.
Yes and no. They have been a distinct groups for that long, in fact longer, out to some 400 million years. And most all would have been outwardly recognizable as "sharks" to the average observer. Yet "unchanged" seems a totally inappropriate word to apply to sharks. Within the broad paradigm of "sharkiness" they've proven highly adaptable and variable.
In modern sharks you have everything from the "normal" mid water predators (some of which must remain constantly moving to "breathe"), to lugubrious bottom feeders like the nurse shark, to huge behemoths like the "whale shark" that filter feed on plankton at the surface like baleen whales. There's similar diversity, with the occasional "odd ball," among ancient sharks. (IIRC there are well over 2,000 species of fossil sharks. Compare to well under 1,000 species among all dinosaurs.)