On the day of the extinction event it was late in the afternoon when the comet struck. There was a miasma of methane (a very volatile greenhouse gas) in the atmosphere. When the comet struck it ignited the gas scorching the lungs of all the dinosaurs on earth, killing them. Yes, this is how it happened.

I guess the largest dinosaur ever found was discovered in Scotland. Maybe his was the fart that broke the camels back. "cept there were no camels.

And the issue of gravity? A non-issue. The dinosaurs had evolved into a very efficient creature. 90% of the gas they generated was stored within the bowel giving each dinosaur a sort of buoyancy or lift which counterbalanced gravity.

Perhaps we could write scientific papers and get them published. Blessings.