520-million-year-old fossil reveals earliest known cephalopod buoyancy system

Half a billion years before the octopus learned to hunt, something barely larger than a grain of rice was already experimenting with the same hydraulic principle that lets cephalopods hang motionless in open water. Thirty-two shell fragments recovered from South China's early Cambrian rocks have pushed the origin of cephalopods back thirty million years, placing their emergence squarely within the great Cambrian explosion of animal life. The creature, Eoceras shaanxiense, carries inside its millimeter-long shell a primitive tube that researchers believe is the earliest known siphuncle — the en