Cisuralian

The Cisuralian, also known as the Early Permian and the Lower Permian,

Fauna
The Cisuralian, a period of well over 20 million years, was - as far as the terrestrial ecosystem went - a fairly stable period ruled over by a diverse selection of pelycosaurs, including the large sphenacodontid finbacks such as the carnivorous Dimetrodon, Ctenospondylus, and Secodontosaurus, all of which attained a lengths of up to 3 meters, as well as semi-aquatic ophiacodonts and the big temnospondyl Eryops and smaller eel-like anthracosaur Archeria.

Life in the Cisuralian was strongly tied to water and to a plant-arthropod-fish food chain; Diadectes and Edaphosaurus were the only herbivores. In this respect it continued the pattern of the great Carboniferous coal swamps. The drier upland was inhabited by a different fauna, mostly smaller insectivores with the herbivorous caseids and proto-therapsid Tetraceratops as significant newcomers. Both in the uplands and the lowlands insects continued to represent an astonishing diversity of forms.

Fish
Fish from the Cisuralian still includes some of the peculiar chondrichthyans of the Carboniferous, such as the engeneodontids, Parahelicoprion and petalodontids, Megactenopetalus, along with primitive sharks, and a variety of ray-finned fishes, platysomids.