I saw an interesting postulation on Twitter that the reason the dinosaurs could grow so large was that there was less gravity during the Mesozoic. My response:

All I know is that, if earth’s gravity was really less for the dinosaurs, it’s one less excuse for them to have not had a space program that could have prevented them being wiped out.

— Rand Simberg (@Rand_Simberg) July 4, 2018