Certarian

The Certarian Period is the fifth and final period of the Plutolithic Era. It is named after Certaria, in the former UBSR. This period saw a rapid period of adaptive radiation among almost all animal phyla, in what has come to be known as the "Certarian Explosion". Many of the most common fossils of this era are from early corals and calcareous sponges known as archaeocyathids. Trilobites also appeared at the end this period, and their remains are incredibly common in its youngest rocks.