Animals During the Ordovician Period

Trilobites

• Trilobites were one of several forms of life that flourished in the Ordovician period. They first appeared in the early Cambrian period and evolved to the point where they became a life form that could flourish in the Ordovician period. Trilobites look something like a primitive, sea-going beetle, and though they flourished in the first stages of life on Earth, all the various species of the Trilobita class are now extinct.

Brachiopods

• Brachiopods were another form of marine life that flourished during the Ordovician period. Like many other forms of marine life of the Ordovician period the Brachiopods originated in the Cambrian period, prospered and then continued to expand their number in the Ordovician period. A Brachiopod is a shelled creature with a hinge, much like a common clam. They were often attached to the sea floor by a long, thin piece of tissue. Though many species of Brachiopods went extinct, some did survive to the current period.

Molluscs

• Molluscs also became more numerous and varied during the Ordovician period. Molluscs appeared in the Cambrian period and possibly even the Ediacaran period, which was the period immediately preceding the Cambrian. Today Molluscs, which are all those species included in the Mollusca phylum, are an extremely common form of marine life, and include oysters, mussels and scallops. After so many millions of years of evolution, there is today a large amount of physical variety within the Mollusca phylum.

Fish

• The first vertebrates, which were fish, appeared during the Cambrian period, which is the period preceding the Ordovician period. Vertebrates began to branch out and evolve further in the Ordovician period, however, and it was not until the Ordovician period that the first jawed fish appear in the fossil record. These first jawed vertebrates would further divide and evolve to become reptiles, birds and mammals, which includes human beings.