Fairly physics oriented- please switch off if not that way inclined.
I've always wondered about 2 things in the dinosaur days (feel free to mail
me privately if you think it's off topic)
1. Was the gravity constant G (F=Gm1.m2) the same in tnose days
2. Was the atmospheric oxygen concetration the same as today?

Reasons being:
1.if G was only 1/2 of today then a 10 ton mass dinosaur would have the
weight of a 5 ton and be able to get about very quickly.
2. If the oxygen level was higher then it would be able to sustain big
creatures with smaller breaths.

Ben Balzer