Edaphosaurus is an extinct genus of synapsids, which were reptile-like animals. Other synonyms for Edaphosaurus are Ophidiosaurus, Clepsydrops, Stereophallodon, Clepsysaurus, and Taenodus. These synonyms are used to refer to various other species of synapsids that have similar anatomy and lived in the same time period. Some of the features that define this group of animals include sprawling legs, a long tail, and a sail-like structure on the back. The sail, made of elongated spines, was likely used for thermoregulation, similar to the function of modern-day lizards. Edaphosaurus lived during the Permian Period, around 300 million years ago, and was one of the dominant herbivorous animals of its time.