Cambrian explosion

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 Read More ›