Hello, Brain corals, like my avatar's Diploria, get their moniker for visually obvious reasons. I wonder whether there are informed hypotheses how come they look that way. The answer to such a question would probably be partly a morphology/pattern formation story, and partly an adaptive story of how such a pattern can increase fitness. Feel free to speculate, but if you can point to actual research, even better :) For the human (and similarly gyrified) brain, the evolutionary explanation is usually that the folding increases surface area and thereby 'computing power' (or some aspect of it). I suppose this is mostly of the cortex (indeed at the expense, space-wise, of the underlying white matter?) and boosts 'higher brain functions'. But for brain corals, I read that the polyps actually sit in the valleys, not on the ridges. So with the ridges taking up space, that does not look like optimally using surface area in terms of simple number of food-gathering polyps. So, where lies the advantage? Current channeling? Predator blocking? ... ? And is the actual shape of the ridges and valleys more coincidental? bonus question: Why are walnut kernels wrinkly, too? Again, 'surface area' doesn't necessarily cut it in an obvious way. Why would a kernel 'need' surface area rather than volume? Most other nut kernels are not (very) wrinkly - they fill their shells. But walnut shells have bulkhead-like structures within the shell - perhaps to increase strength? [NON-TELEOLOGICAL EDIT: perhaps this increases strength?] - and kernel shape may be an adaptation to that...?