Being big, is good up to a point. After that you just get heavy and slow. Some dinosaurs had wings but where too heavy to fly. Some had long neck, but would pass out from blood loss if they used them to reach for anything, and some predators where so heavy the couldn't run. When you listen to paleontologists argue about the limitations of dinosaurs, you get the feeling that dinosaurs were not designed very well. It doesn't sound like something evolution would do.
I think that Paleontologist are looking at it all wrong. Instead of trying to figure out how these animals coped with physics, evolution probably made them perfect, It was the physics that was different. My theory is that the effective gravity was lower 65 million years ago.
No, I don't believe that the laws of physics have changed, Earth probably had comparable mass, but earths rotation is slowing down. If we imagine a past version of earth spinning a few times faster, the centrifugal force starts to counteract gravity.
If gravity was substantially lower, the brontosaurus could walk on land and raise its head without passing out because of blood loss, a tyrannosaurs would be able to run and the massive birds would be able to fly. They would all make sense from an evolutionary point of view.
Even today gravity is slightly lower at the equator, and earth is slightly flattened as the pols. It is a very slight, but if we look at the equation for centrifugal force we find that its velocity to the power of two divided by the radius. The power of two, means that the fairly insignificant centrifugal force quickly becomes very significant if we increase earths rotation.
The faster you spin the planet the further out the equator is pulled, and the further the distance between the center of earth and the equator, the stronger the centrifugal force becomes (the increased radius decreases the force, but the increased velocity makes up for it as a point on the surface has a longer distance to travel per revolution). If earth would spin at around 90 minutes per revolution, the centrifugal force would be so strong it would pull the planet apart. The equator would break lose from the surface and form the kind of rings we see around Saturn.
If we imagine that an earth day was only a few hours long in the Jurassic period, evolution would develop larger animals due to the lower effective gravity. If this theory holds up and earth rotation greatly influenced the effective gravity on earths surface, it would only do so close to the equator. Therefor you should only be able to find fossils of dinosaurs in areas that were reasonably close to the equator at the time.
I have never ever read anybody suggest this as a theory, and every time I read some article about how paleontologists argue about the limitations of dinosaurs, I think of this idea. I don't claim to be an expert, but I think its in the grand tradition of science to propose ideas, and then let others try to prove or disprove them. So please let me know how right or wrong you think I am.
While thinking of this I also discovered a new continent. Yes, I have found a continent, and I'm naming it "Eskil" (I mean, what the hell... if you don't like it i got there first). I do admit its a little like Democritus naming the Atom, or Higgs theorizing about his Boson, and then letting thousands of unnamed scientists spend years of research and millions of dollars trying to prove you right, but what can I say? I'm a busy guy, got places to go, people to meet and all that. So here we go:
Its commonly accepted that the tectonic palates once had all continents joined together to form a massive super continent commonly known as Pangaea. If we imagine that the weight of all continents where concentrated on one side of our planet, the center of gravity would shift towards that side. Yes, earth surface only makes up a tiny fraction of earths mass (most of earths heaviest metals has sunk to the core), but remember everything beneath the surface is fluid, therefore the core would move to be suspended in the center of the gravity of the surface. If the plants center of gravity would move towards this one continent, all liquid water would follow, an the sea level on the side of Pangaea would rise, and lower on the opposite side revealing a new land mass: Eskil.
I think its time to stop now, and go back to work.