Mean atmospheric O2
Geologic Time Scale
Giant, 20-foot-long and one-ton synapsids of the genus Cotylorhynchus forage in an Early Permian swamp 275 million years ago in what is today North America. Also in this image on the lower left is a 3-foot long lepospondyl amphibian of the genus Diplocaulus. Vegetation includes ferns and horsetails in the foreground and on the horizon is a forest of ginkgos.
Cotylorhynchus is the largest known non-mammalian synapsid and was the largest land animal of its time. An herbivore, Cotylorhynchus had a massive barrel-shaped body and limbs with a relatively small head, making it perhaps one of the most unattractive land animals to have ever walked the Earth. Standing about 6 feet tall at the shoulder Cotylorhynchus probably had no predators; even the fierce Dimetrodon (also a synapsid) weighed little more than 300 pounds compared to Cotylorhynchus' 2,000.
Copyright © Walter B. Myers. All rights reserved.
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