(ScienceDaily June 4, 2012), we learn,
Giant insects ruled the prehistoric skies during periods when Earth’s atmosphere was rich in oxygen. Then came the birds. After the evolution of birds about 150 million years ago, insects got smaller despite rising oxygen levels, according to a new study by scientists at the University of California, Santa Cruz.
nsects reached their biggest sizes about 300 million years ago during the late Carboniferous and early Permian periods. This was the reign of the predatory griffinflies, giant dragonfly-like insects with wingspans of up to 28 inches (70 centimeters).
“Maximum insect size does track oxygen surprisingly well as it goes up and down for about 200 million years,” Clapham said. “Then right around the end of the Jurassic and beginning of the Cretaceous period, about 150 million years ago, all of a sudden oxygen goes up but insect size goes down. And this coincides really strikingly with the evolution of birds.”
With predatory birds on the wing, the need for maneuverability became a driving force in the evolution of flying insects, favoring smaller body size.
The findings are based on a fairly straightforward analysis, Clapham said, but getting the data was a laborious task. Karr compiled the dataset of more than 10,500 fossil insect wing lengths from an extensive review of publications on fossil insects.
The authors’ idea shuld be considered with caution, for reasons they themselves admit, but it is an interesting suggestion.
An animation of a conflict between an early bird and a giant insect would be great.
See also: Do really big life forms require 3-D (marine) hunting?
Dinosaurs doomed by egg-laying (size ratios said to be unfavourable compared to mammals)
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