Somebody mentioned it before, but the latest accepted theory among the "educated" is a M-A-S-S-I-V-E Volcanic event in the wilds of Russia, released enough lava to cover the entire United States in many many feet, and the resultant gases and such had a major climate change effect.
This was closely followed (in geologic time) by the Chicxulub event in the GOM, which had its own environmental effect along with setting the entire world ablaze.
However, nowhere in the world has there been found ANY dinosaur above this KT boundary of the chixulube event. You would think some would've died later, farther away and been mixed with the fallout layer blanket coming down to layer the earth. but nada.
Which leads scientists to think the dinosaurs where already deadified when chixulube hit.
So... you're saying God double-tapped them?
