Sunday, September 12, 2010

Cambrian Explosion Evidence: Burgess Shale Fossils aren't Alone

"Ancient Animal Explosion Gets Bigger With New Finds"
Animal News, Discovery News (September 9, 2010)

"Eight new kinds of the earliest animals from the Cambrian Explosion have been found in a newly explored section of ancient rock in Canada.

"At least eight new kinds of Earth's earliest animals from the mysterious and controversial Cambrian Explosion have been discovered in a unexpected section of ancient rock 30 miles from the famous Burgess Shale of Canada. The discovery suggests such old, rare fossils are more common than previously thought.

"Like the fossils of the original Burgess Shale, the new discoveries are remarkable because they preserve features of animals which had only soft parts -- like gills and eyes -- and remained intact for more than half a billion years.

"That's a time when animals evolved from being very small, simple organisms into a wildly creative, explosive variety of sometimes bizarre creatures. These were culled by natural selection over time, leaving the more familiar main animal groups we see today.

"Among the more dramatic discoveries is a new kind of 'anomalocaridid' -- the monster shrimp-like top predator a half-billion years ago. Some of these sorts of beasts have been found up to two meters long in shale from Chengjiang, China...."

We've known about the Burgess Shale fossils for a long time - but it looked like that treasure-trove of detailed soft-bodied fossils was a fluke. The Burgess Shale formation happened when fine silt fell off an underwater cliff, burying critters swept up in the avalanche.

The new find is from shale that formed from fine mud that was on a gently sloping surface - and preserved tracks of the buried critters. That strongly suggests that the creatures lived near where they were found. And that the sequence of events needed to preserve the fossils isn't as rare as we thought.

Besides the new Canadian discovery, similar fossils have been found in China, Greenland and Australia.

Looks like paleontologists will have a great deal more data to work with.

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