Thanks for this excellent summary of the current state of interpretation of
the fossil record of the Precambrian-Early Cambrian. I have no
disagreement with most of what you have reported. I would add that in the
southwest, where I have done most of my work, the base of the Cambrian is
most often delineated by the appearance of the first trilobite above what
is otherwise a generally unfossiliferous section of Precambrian sediments.
This gives a somewhat different insight to your comments regarding the
situation in some other parts of the world. I would still argue that the
data thus far available that I have seen does not support the existence of
podopods before trilobites.
Art
http://biology.swau.edu