Some dinosaurs were huge. Their massive size is one of their most intriguing features. For children and adults alike, it is hard to imagine how they grew so huge. Possibly, it is because the earth was going through a cycle of lesser gravitational force. With a smaller gravitational force these creatures could have grown to much larger size than seems possible today. (Imagine how nimble an elephant would feel on the moon's surface with its smaller gravitational force!)
Since the dinosaur's mass extinction happened most recently of the three previously mentioned -- just a mere 65 million years ago -- and assuming that earth goes through cycles of decreasing and increasing gravitational forces, then the Ball-of-Light Particle Model predicts we are at a point where gravity is roughly medium and is on the decreasing leg of the cycle.
Graphic of max gravity dinosaurs died, a little more than a fourth of the way around from that.
If dinosaurs really did develop during a cycle when gravity here on earth was low, and if the earth then went through a swing between the Cretaceous and Tertiary periods where gravity increased, then this would have created an extinction factor that would "picked on" the larger dinosaurs. This seems to be just the case. While there seems to be many factors that could have killed off the dinosaurs -- solar eruptions, changing weather, changing weather due to solar eruptions, increased volcanism, earthquakes, increasing numbers and maybe massive impacts from meteorites -- the extinction of the dinosaurs occurred over millions of years and seemed to kill off a higher ratio of large animals than small animals.
The Extinction of the Dinosaurs