From Nature:
The fossils, along with two other creatures discovered by Strausfeld and his team, also show that the three main kinds of arthropod brains have been around for more than 500 million years, even as their bodies changed drastically.
As top predators of their age, anomalocaridids may have spurred the evolution of the more sophisticated brains of the other arthropods they preyed upon, even though their nervous systems remained comparatively simple, Strausfeld says.“A predator that’s cruising around looking for prey doesn’t need to have a very complicated brain. It doesn’t have many enemies.”
Hmmm. As a toss-off statement, that sound impressive, but it isn’t necessarily true.
Maybe the anomalocaridids had no predators themselves, even when they were young, but most predators do. In many ecosystems, it would be unwise to assume that the top predators can afford to be stupid, even in adulthood (= have an uncomplicated brain). See the vids below.
See also:
Trackways show, animals 50 million years ago used Levy random walk to search for food. Actually, the findings don’t necessarily explain why modern animals use the technique. They don’t do the math either.
and
Salamander rule 1: Stroke ain’t broke, so don’t fix it – for 270 million years. Or more, when necessary. Talk about stasis!
This does seem to be Stasis Day at Uncommon Descent, but now and then three is just a crowd, maybe not a trend.
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It can go either way for the poor ol’ invert: