The Seven Arm Octopus

There are octopuses which are very, very special and bits of sea grass. There's a spider crab called macrochiera campfairy that you see every now and then on the internet. And also other animals which have odd numbers of legs. Do you guys know about the tripod fish? No. It has three long protrusions that come off its fins. So it can detect vibrations in the seabed if predators are coming. I reckon that might be the closest other animal there is tapping three.