The sea-scorpion is an average-sized sea creature resembling a terrestrial scorpion, and which has a rather unique feature: Despite an apparent lack of spines, claws, or other obvious methods of cutting, anyone who attempts to pick up the sea-scorpion will end up with a painful cut on their hand. This cut will manifest no matter where the sea-scorpion is grabbed. What features might the sea-scorpion have that would allow for this bizarre wounding?
A caraspace that contains a coarse, sharp, abrasive (similar to that of a coarse sharpening stone, but I have recently discovered that the coarseness of a dressing stick for a grinding stone is much much worse). Combined with the instinct to twitch or make sudden jerky movements When picked up. In particular, having angled edges or ridges or tiny raised conical or triangular dimples will greatly help with this by concentrating pressure.
I did this to my fingers last week when washing a dressing stick. I was aware the edges of the stick were sharp but failed to pay sufficient notice to the fact one of the end faces had a small imperfection. Just a couple of dimples sticking out smaller than your typical grain of sand. But unlike a grain of sand, it was pointy, very sharp, and wouldn't move with your finger if your finger grazed it