The way the theory actually works is "big dinosaurs" died out, the smaller ones became for the most part modern day birds and lizards (and some animals have lived the entire time) Check out "Archaeopteryx", Coelacanth (a long held belief this fish was extinct, Then they found tons of them around Africa, why you ask did no one know about this, Natives said "it tasted like dirt",so no one kept any to give or show to a naturalist or biologist....), The Megalodon Shark (great white about 50-75 feet long AHHHH, apparently went extinct within the last 25,000-50,000 years yet was around since the Cetaceous I believe). Most sharks, turtles,crocodilians, insects havent died out at all , just became smaller to adapt. Not so hard a stretch to see dino's surviving *(just not large ones ie: allosaurus , ultrasaur's, diplodocus, and my fave Tyrannosaur's). Plus according to fossil records at one point almost 98% of life was wiped out on earth, now thats a scary thought. Although I'm kind of thankful large dino's didnt survive (or at least I hope they didnt, After all "nessie" or other "pleiosaurs" may exist to this day, the ocean is a wide place , just recently they've proved the existence of giant squids also known centuries ago as "krakens",most people considered the whole thing foolish to even think of now its fact(found in sperm whales apparently their favourite food), also over 100 species are discovered everyday ....)