SSS 2008-05-07

（单词翻译）

This is Scientific American's 60-Second Science,I am Steve Mirsky.Got a minute?

It’s accepted that a large meteor impact 65 million years ago was responsible for the mass extinction¹ of the dinosaurs².  Which opened up niches³ for birds and mammals.  But last week at an evolution conference at The Rockefeller University in New York City, New Zealand biologist David Penny questioned whether the dinosaurs might not have already been on their way out. Penny concentrated on fossils of pterodactyls and birds. Turns out that the average wing spans of pterodactyls had been getting steadily⁴ larger before the big impact. By the time the meteor hit, pterodactyls still making a mark in the fossil record had wingspans well over 30 feet.  Meanwhile, it looks like the Cretaceous version of shore birds were becoming relatively⁵ common, based on fossil findings.  So perhaps the smaller pterodactyls had disappeared because the new kid in town, birds, were out-competing them. Penny’s view was certainly not uniformly accepted by other meeting attendees. But it’s an interesting question, whether the meteor might have been not the first strike, but the last straw.

Thanks for the minute,for Scientific American's 60-Second Science,I'm Steve Mirsky.