Dinosaurs survived and thrived for 165 million years -- far longer than the roughly 300,000 years modern humans have so far roamed the planet.
They lived on every continent, munched on plants, snapped their jaws at insects, itched from fleas, suffered from disease, got into fights,
snoozed, performed elaborate courtship rituals and looked after their young. The creatures were much more diverse
-- and downright bizarre -- than what we might recall from childhood books.
Were it not for an asteroid strike 66 million years ago, the ancient creatures still might have dominated our world
. And they still are here, in the form of birds we see around us today.
Scientists have discovered more in the past two decades than they had in the prior 200 years about how dinosaurs behaved and evolved. Here's what's new and different about what is known of dinosaurs.
How many dinosaurs were there?
The short answer: Lots.
Take T. Rex, the predator with banana-sized teeth that is perhaps the best studied dinosaur. Scientists believe that each T. rex generation was 20,000 individuals
, and this adds up to a total of 2.5 billion during the 2.4 million years the