@dyslexia,
The data that supports a "Not so Big Cambrian Explosion" has gotten pretty huge of late.
In the last 3 years , fossil evidence showing that life had already expanded into its 3 major superphyla by the NEOARCHEAN (2.8-2.5 Bya) was uncovered in the northern Canadian archean sediments. In the last year, sveral examples of complex animals were found in the Rhyacian sediments of the Proterozoic (about 2.1 Bya). These animals were of the types like mollusca and annelids that serve as goo examples of root stock of later forms that diverged in the excess O2 conditions of the late preCAmbrian and early CAmbrian. So the "Cambrian Explosion" is more correctly , the "Shell Explosion" for the excess O2 enabled the mollusca and gastropods and Bryozoans and trilobites to put on hard shells to act as further protection or as external skeletons to allow them to attain greater sizes.
Several key phyla were discovered in these 2.1 By deposits .
I would imagine that, over the next yer or so, there would be several summary articles or even a book or two about how the development of complex animals was actually a longer process than the earlier legend had us accept.