Could high air-pressure explained huge dinosaurs?
Well … I had a look around, and it looks like there’s a review article out: The Evolutionary Physiology of Animal Flight: Paleobiological and Present Perspectives Robert Dudley (Annual Review of Physiology Vol. 62: 135-155 (Volume publication date March 2000) ▪ Abstract Recent geophysical analyses suggest the presence of a late Paleozoic oxygen pulse beginning in the late Devonian and continuing through to the late Carboniferous. During this period, plant terrestrialization and global carbon deposition resulted in a dramatic increase in atmospheric oxygen levels, ultimately yielding concentrations potentially as high as 35% relative to the contemporary value of 21%. Such hyperoxia of the late Paleozoic atmosphere may have physiologically facilitated the initial evolution of insect flight metabolism. Widespread gigantism in late Paleozoic insects and other arthropods is also consistent with enhanced oxygen flux within diffusion-limited tracheal systems. Because total atmospheric press
There is a oft-criticized theory in evolutionary biology called Cope’s Rule that hypothesizes that organisms tend to get bigger with time. Bigger animals (for plant-eaters) mean they can fight off predators more easily; the predators tend to get bigger as a result, then the plant eaters get bigger, etc. The classic example is the size of horses through time. Dinosaurs got bigger during the Mesozoic; mammals got bigger during the Cenozoic (mammoths and sloths, anyone?). Don’t forget, some of the largest species to have ever lived are around today, like the giant sequoia and the blue whale. An experiment for your idea could involve gathering evidence on the sizes of organisms at higher elevations and sea level and statically see if size is related to the pressure difference. But you would find that morphology corresponds more to climate and nutrient availability – such as oxygen or phosphate – than something like air pressure. You see the same pattern among organisms at latitude as you d
I’ve heard from several places (but none really authoritatively) that the ancient atmosphere may have contained much more oxygen. Oxygen in the air, to be precise. Some scientists think that the air at the time of the dinosaurs contained a lot more oxygen gas than it does today. Since the oxygen animals breathe is used in chemical reactions that power their muscles, more oxygen in the air might have made it possible for dinosaurs to get more oxygen into their muscles. That could have made them much stronger than animals today—strong enough to carry around huge bodies. It might also explain how sauropods managed to breathe through those long, skinny necks of theirs. To see why that’s a problem, try putting a drinking straw in your mouth and breathing through it. Quite a challenge, isn’t it? But it would be easier to breathe if the air had more oxygen in it. The evidence for more oxygen in the air at the time of the dinosaurs comes from bubbles in 100-million-year-old amber, tree sap tha
