We believe they did, in fact! Not technically in the mandibles themselves, but in the clypeal horn, on their foreheads. Micro-CT scans indicate high density around where the mandibles articulate with the horn, which is thought to be bioaccumulated metal reinforcing the horn during mandible closure

Thanks for the follow list! Okinawa is great and so are the hermit crabs - found the cutest Ryukyu pottery mug with blueberry hermit crabs