October 2008 (UTC)

The fossil record does provide some constraint, as explained in the ref.  As I recall, in simpler terms, the argument was that given the constraints that could be put into place on the clocks, they show that more diversification happened during the Cambrian explosion than usual.

Incedentally, doi:10.1641/B580912 might be of interest: it is an overview of the Cambrian explosion whose structure bears uncanny resemblance to this article.  It may contain some snippets worth including or ideas for how to contract/expand the main article.  ( – Talk) 19:53, 25