Chapter 3 - The Ordovician, Silurian, Devonian, and Carboniferous

On the bottom-left is the Ordovician.  The warm waters of the Ordovician covered much of the earth, submerging the continent that would later form North America.  The oceans teemed with trilobites: large pillpug-shaped creatures that scuttled across the seabed.

On the bottom-right is the Silurian period.  During this period, coral reefs flourished, providing habitats for many of the first fish.

On the upper-right side shows the Devonian, also known as the Age of Fish, and I can see a giant Dunkleosteous fish!  It uses those big plates in its mouth as teeth.  Dunkleosteous doesn't have real teeth.

On the upper-left is the Carboniferous period, and right over there next to that Sigillaria tree, there is a giant amphibian.