Ordovician

Animate the Continental Drift

New Species:

• First corals
• First land plants

Warm climate, followed by global cooling and glaciation		High sea levels at first; North America under shallow seas		Primitive plants appear on land		Primitive fishes, bivalves and gastropods		None

The Ordovician is best known for the presence of its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and some early vertebrates. A typical marine community consisted of these animals, plus red and green algae, primitive fish, cephalopods, corals, crinoids, and gastropods. Evidence also suggests that plants invaded the land at this time.

In the early Ordovician, the climate was mild, with a lot of moisture. As the land masses moved towards the south Pole, however, massive glaciers formed, causing the sea levels to drop. This may be the cause for the large extinctions at the end of the period, which affected almost 60% of the marine invertebrates and 25% of all families.