All they've left us are their fossils, the dried-out mineral remnants of the creatures they once were, with the organic material that gave them life long gone. Or so everyone always thought.
Until B. "Rex," a 68 million year old Tyrannosaurus Rex, who was dug up and named by a paleontologist from Montana State University whose unorthodox approach to dinosaurs may be changing the whole dino ballgame.
When thinking of dinosaurs, most of us think "Jurassic Park," the 1993 classic film about a dinosaur resurrection experiment gone wrong, and its embattled hero, famed paleontologist Alan Grant.
60 Minutes correspondent Lesley Stahl met Jack Horner, the real-life Alan Grant who consulted on all of the "Jurassic Park" movies.
Fortunately for him, Horner joked, Grant didn't get eaten.
Jack Horner is one of the most prominent and controversial paleontologists in the country - a dyslexic MacArthur Foundation genius who never finished college, and who says he doesn't care why dinosaurs went extinct.
To him, the important part is how they lived. "I'm trying to figure out the biology of dinosaurs and what they were like as living creatures," he told Stahl.
"You wanna know what their behavior was, how they treated their young," Stahl asked.
"I wanna know everything we can know about them and make one if we can," he replied with a smile.
Make a dinosaur? The things Horner says make him a maverick, but the finds he has made, including more T. Rexes than anyone else in the world, make him a legend.
One of his finds include the teeth of the oldest T. Rex ever found, which Horner pulled out of a drawer in the Collections area of his Museum of the Rockies in Bozeman, Mont., and showed Stahl.
"This little pocket right here in the teeth is where the next tooth sits. Dinosaurs replace their teeth throughout their life. And T. Rex replaced all of their teeth every year," Horner explained.
But Horner is most famous for discovering a kinder, gentler side of dinosaurs.
In the badlands of Montana, he and his team uncovered the first dinosaur nesting ground in the world - a vast landscape full of eggs, nests, and babies that helped change our image of dinosaurs.
Thanks to Horner's influence, "Jurassic Park" showed that most dinosaurs were social animals who lived in colonies, and he has found evidence they actually cared for their young.
"So, this is the tibia, the shin bone. And this is a little less than a month old. And here, here is the same bone," he told Stahl, showing her a much bigger bone.
Stahl assumed the larger bone belonged to an adult, but Horner corrected her: though much larger, this specimen belonged to a one-year-old.
Horner figured out that such rapidly growing baby dinosaurs couldn't walk at first, meaning their parents were bringing food back to them in the nest, like birds. His discoveries lent support to a then-controversial but now widely accepted theory that dinosaurs actually gave rise to modern birds.
"If a little kid today who studies all this in school and they look up in the sky and see a bird and turn to mom and say, 'You know, that's a dinosaur'…," Stahl remarked.
"They're right," Horner replied.