This is Siphusauctum gregarium, a creature that lived in the ocean 500 million years ago. It's so completely strange that it's taken scientists 30 years just to figure out how to describe it. It's literally like nothing else on Earth.
Many of the creatures that lived in the seas half a billion years ago were far too soft to leave behind many fossils. But their footprints remain, and one of the most striking finds is a giant, predatory sea millipede.