The first known cephalopod was only a millimetre long and lived about 520 million years ago

TL;DR - Fossils of the millimetre-sized Eoceras indicate that cephalopods existed around 520 million years ago, earlier than previously established.

• Eoceras possessed a siphuncle, a structure used by modern cephalopods for buoyancy control.
• The fossils date to the early Cambrian.
• The discovery identifies the earliest known cephalopod and pushes the group’s origins further back in time.