The finding points to a long-held suspicion about dinosaurs: they got bigger as oxygen in the atmosphere slowly crept up over millions of years. By the time it peaked at 23 percent in the Cretaceous period, huge sauropods and giant predators like Tyrannosaurus Rex ruled the planet. Owerkowicz stressed that his experiments "just scratch the surface" of understanding the connection between reptilian physiology and oxygen levels, and that the size-oxygen relationship is not at all clear. And as John VandenBrooks of Arizona State University pointed out, more isn't always better. In separate experiments, VandenBrooks found that alligator embryos started to show signs of damage when incubated in environments above 27 percent oxygen. "About 27 percent you start to see increased free radical production and ozone production, which increases damage to cells and tissue," he said. "You lose the positive effects." Either way, Owerkowicz said understanding how dinosaurs lived in the ancient world will mean considering the strange and varying atmosphere they breathed. "You cannot assume the metabolic rates of animals living under hypoxia were similar to today's," he said. "Metabolic rate affects everything an animal does. What speeds could the animals run at? How much food could they digest? Oxygen would have a huge impact on all of that." Related Links: |
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