0 Dinosaurs left after the asteroid strike 66 million years ago (well non-avian ones anyway).
I hope this dinosaur trail teaches you about their huge variety. If you find all the hides, then Challenge caches for finds starting with every letter of the alphabet and 0-9 will be earned for you. Just go sign them.
There are a few special characters mixed in and there are challenges that want some of these too. I'll likely add a few extra specials past this spot on the trail in time.