The Fruitiness of August. The Silurian. Marine life

Much of the landmass that would become western North America was under a shallow ocean for much of the Silurian Period. These shallow waters enabled sunlight to penetrate, and marine animals underwent rapid differentiation. Silurian fossils show extensive coral reefs built from tabulate and horn corals with calcium carbonate skeletons. In the early Silurian, a class of jawless fish, Agnatha, similar to modern hagfish and lampreys, was most common. In the mid-Silurian, the first species of Romundina, a Placoderm — a primitive armored fish with a cartilage skeleton — is earliest fish known to have developed jaws.