"sharks are older than trees" is technically true, but TIL that sharks were a marginal group until the mid-Jurassic (the middle of the Dino Age, ~200-150 mya), and all modern shark orders first appear around this time.
Before then, a different group of cartilaginous fish called hybodonts were the big apex predators. How were they different than sharks? Mostly because they had "boney" dorsal spines made out of dentine and enamel. Like teeth are. Like where would that tech have gone, if they'd survived and kept evolving for 200 million more years?
TIL that sharks went thru a mysterious extinction event 19 million years ago, when 95% of populations and 70% of species disappeared. Sediment samples go from having 1 shark fossil for every 5 fish fossils, to 1 shark per 100 fish (does that mean that the ocean used to be like 16% shark??)
And there was no big climate change then, or extinctions of other groups! This research is pretty recent and no one has even an educated guess!
Two effects of this:
All of today's big ocean sharks (Great White, Tiger, Basking, etc.) all evolved from coastal sharks that survived this event. And,
Populations haven't recovered. Sharks as a group are still decimated, a shadow of their former selves for most of the last 200 million years.
