There's very little evidence to suggest that dinosaurs were cold blooded. Some even lived in Arctic environments, look it up. No. Dinosaurs did grow that large because of the high levels of oxygen available at that time, blue whales grew so big because they live in water. The water allows their massive body mass to stay afloat and not cave in on itself. A land animal requires much more oxygen than any aquatic born one.
http://www.smithsonianmag.com/history/the-strange-lives-of-polar-dinosaurs-180347471/ literally the first link I that came up when googled. The natural history museum in London even has a whole exibit dedicated to polar dinosaurs.
And as for the second point, look at it this way: who takes more breathes during a race, a competition swimmer or runner?
I was talking about the oxygen thing. And this idea doesn't really say anything. Is there any scientific evidence that higher concentrations of oxygen allows for larger lifeforms? -Yuri
OK so.... The article claimed that there were 2 jumps in body size, and both jumps corresponded "almost perfectly" with rise in oxygen concentration. Here is their chart As you can plainly see, for many millions of years, body size increased, before the oxygen did, and also decreased before that increase. The article also points out that the oxygen concentration was a direct result of more photosynthesis. So the same data would also suggest simply that access to food caused larger body sizes. Obviously before oxygen could rise, plants had to grow. Their chart suggests that dinosaurs and plants grew with eachother, and the oxygen wasn't a direct cause. The reason life today is small could simply be because smaller more numerous organisms are better suited to surviving large scale natural catastrophes. This link doesn't really prove that higher concentration of oxygen is required for larger animals. -Yuri