"ScienceDaily (Oct. 30, 2010) — The giant dragonflies of ancient Earth with wingspans of up to 70 centimeters (28 inches) are generally attributed to higher oxygen atmospheric levels in the atmosphere in the past. New experiments in raising modern insects in various oxygen-enriched atmospheres have confirmed that dragonflies grow bigger with more oxygen, or hyperoxia." (Source)For more on this interesting subject:
"Our main interest is in how paleo-oxygen levels would have influenced the evolution of insects," said John VandenBrooks of Arizona State University in Tempe. To do that they decided to look at the plasticity of modern insects raised in different oxygen concentrations. The team raised cockroaches, dragonflies, grasshoppers, meal worms, beetles and other insects in atmospheres containing different amounts of oxygen to see if there were any effects. (Source)
One result was that dragonflies grew faster into bigger adults in hyperoxia. However, cockroaches grew slower and did not become larger adults. In all, ten out of twelve kinds of insects studied decreased in size in lower oxygen atmospheres. But there were varied responses when they were placed into an enriched oxygen atmosphere. VandenBrooks is presenting the results of the work Nov. 1 at the annual meeting of the Geological Society of America in Denver. (Source)
"There have been a lot of hypotheses about the impact of oxygen on evolution of animals, but nobody has really tested them," said VandenBrooks. "So we have used a two-pronged approach: 1) study modern insects in varying oxygen levels and 2) study fossil insects and understand changes in the past in light of these results." (Source)
A few dozen T. rex bones have been looked at by a Yale University paleontologist. He found three foot bones and one arm bone that showed evidence of T. rex bite marks.
"It's surprising how frequent it appears to have been. We're not exactly sure what that means," Nick Longrich said in a Yale news release. (Source)More Articles:
"Modern big carnivores do this all the time. It's a convenient way to take out the competition and get a bit of food at the same time," Longrich said. (Source)
"These animals were some of the largest terrestrial carnivores of all time, and the way they approached eating was fundamentally different from modern species. There's a big mystery around what and how they ate, and this research helps to uncover one piece of the puzzle," Longrich said. (Source)