Ordovician

Ordovician is the third era in this game. there are 4 organisms in this era. The requirement for unlocking this era is researching Vertebral.

Trivia

 * Nautilus is one of the largest creature before Camarasaurus in Late Jurassic. Its size is similar to Dunkleosteus and Plateosaurus.
 * This era spans from 485 to 443 million years ago.