Greg’s Dinosaurs Riddle

The two-riddles post was a success, and while corresponding with Greg Kuperberg he had a riddle for me about dinosaurs, and he agreed I will share it with you.

Right before the Chixculub asteroid hit the earth, there were a variety of mammals and a wide variety of dinosaurs.  Both the mammals and the dinosaurs lived in many places, came in many sizes, etc.  Why did some of the mammals survive, but none of the dinosaurs did?

A nuch simpler question: Can you answer (without clicking or googeling or so):

How many years did the dinosaurs live? (you know,.. not a single one but them as a whole…) 1 million years, 5 millions, 20 millions, 50 millions, 100 millions?

And a deep philosophical question:

The dinosaurs perished. Should we regard them as losers???