http://www.sciencemag.org/news/2019/09/rock-munching-sea-urchins-have-self-sharpening-teeth

Sea urchins’ spines aren’t the only sharp part of their prickly bodies. The sea creatures’ five razorlike teeth (above) are self-sharpening—and a new study suggests scientists may be able to harness this power to make cutting-edge tools that rarely require extra honing.

Sea urchins are well known for their ability to chomp through just about anything; they use their small, star-shaped mouths to crunch on brittle starfish, coral reefs, or even rocks. Scientists long suspected the urchins’ ceramic teeth sharpened themselves, but no one could figure out exactly how they did it.