lowermost and oldest major division of continental rocks and time of the Pliocene in North America (the Pliocene Epoch began about 7,000,000 years ago and lasted about 4,500,000 years). The Clarendonian Stage, which follows the Barstovian Stage of the preceding Miocene Epoch and precedes the Hemphillian Stage, was named for exposures studied near Clarendon, Texas, and is characterized by the presence of distinctive mammalian fossil forms. The Clarendonian has been correlated with the Sarmatian Stage of European usage.