Off topic, I know…
but a Nature article (Fox 2016) highlighting Ediacaran and Cambrian fossil fauna sparked this quick blog post.
Missing from the published hypothesis
are all the various unfossilized flat, ribbon and round worm morphologies that were precursors to the various deuterostomates and protostomates that are found in Cambrian sediments. You can read more about those in my 1991 book, From the Beginning, pdf here).
Fox D 2016 (journalist). What sparked the Cambrian explosion? Nature 7590 pdf