The planet’s gravity had to be about a third of what it is today for the dinosaurs to live. In today’s gravity they would all collapse and die. No land animal can be larger than an elephant. So, if geological dating is correct (a big “if”), then the Earth’s gravity increased significantly sometime around 65M years ago, and then again when the giant mammels disappeared.
This is literally one of the kookiest things I've ever read on FR, and there's been some doozies.