First Cephalopod
 |
The earliest known cephalopod was Plectronoceras Cambria which emerged in the Cambrian, 540 Ma(million years ago). It was found in the Fengshan Formation of northeast China. It was a Nautiloid and its distinguishing feature was that the shell enclosed an air space which provided buoyancy. This evidence can only be recognized by the observation of septa with a siphuncle or tube for the extraction of water from its chambers. |
| Figure 8: Plectronoceras Cambria, an early cephalopod (a) Specimens from the late Cambrian of Shantung, China (b) Inferred restoration of soft parts with shell partially removed to show mantle cavity with gills |
 |
 |
 |