The Ordovician Period

The first fossils found are from this period The first fossils found are from this period. All life existed in the seas which covered most of the Earth’s surface. There was lots of flooding and warm shallow seas. The Earth was probably warm at this time.

There were two groups of animals. 1 There were two groups of animals. 1. There were animals that floated or swarm near the surface of the sea 2. There were animals that could swim in deeper waters and root themselves on the sea beds. These two groups develop differently.

Animals with shells become more popular Animals with shells become more popular. Shells were different sizes and shapes. We begin to see starfish, sea urchins and nautiloids.

Nautiloids Nautiloids are a cone shaped cephalopod. They were mighty creatures of the sea. They ate trilobites. They could be 5 meters long. They could curl up to protect their soft underside. They eventually became extinct.

Crinoids Crinoids are sea lilies. They covered the ocean floor. Crinoids were anchored to the floor and were echinoderms. They had a stalk to support their top. They would wave back and forth to catch their food.

Coral Reefs and Eurypterids Coral reefs were also expanding during this time. Marine scorpions called Eurypterid, were developing during the Ordovician Period.

Graptolite Graptolite lived during this time. They are a very interesting animal. They are a coelenterate. They lived in groups. Sometimes they would root themselves to the bed of the sea or float freely in the water. They are thin with a shell like covering arranged like leaves on a branch. The graptolite would also group together to travel throughout the water.