This was bound to come up eventually:
First, notice the quote marks around “Cambrian explosion,” a subtle hint that the term is controversial. It’s not. They state clearly that it is “marked by the appearance of most major animal phyla.” Panarthropoda is a taxon that combines arthropods with tardigrades and onycophorans. The sentence means that yes, lots of different arthropods appear throughout the fossil record, revealing “extreme morphological disparities,” i.e. outward differences.
Yet these Chinese specimens show that the brains are conservative — not that they vote Republican, but that CNS structures throughout the panarthropod collection are similar, not showing extensive evolution. They’re not just conservative; they are “remarkably conservative.” In terms of general body plan, it’s a picture of sudden appearance and then stasis for the rest of time — not exactly what Darwin hoped the fossils would demonstrate.
You can read this open-access paper and appreciate the delicate features preserved in these fossils. The authors present a theory of taphonomy (the study of how things fossilize) to explain what they see.David Coppedge, “Darwin Wept: Cambrian Brains and Other Challenges for Evolution” at Evolution News and Science Today (April 21, 2022)
Sure they do.