Thread: Possible trigger for Cambrian "explosion"
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Old 10-July-2009, 05:15 PM
AndrewJ AndrewJ is offline
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Originally Posted by jlhredshift View Post
If they are correct then either the "primitive ground huggers" were resistant to ultra violet or an ozone shield had been established by that time.

That's what I thought: that the spread of life to land was only possible once a protective ozone layer had been established around 500 mya.

Regarding the Cambrian expolsion, was it not that a tipping point of sophistication had been reached whereafter animals tended to have skeletons that could form fossils?
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