Discovered in the late 19th century by Edward Drinker Cope, Edaphosaurus has, like many paleontological finds, undergone many perceived behavioral changes and natural niche assignments since its discovery. Initially the teeth of the animal led researchers to believe in a main diet of mollusks and other such aquatic creatures. Over time, though, many have noticed very herbivorous traits in the animal such as cutting teeth at the front of its mouth designed for slicing off vegetation. The overall body mechanics of the Edaphosaurus indicate slower speed of movements much more consistent with modern large herbivores as well.
The sail on Edaphosaurus' back was different from that of Dimetrodon in many ways also, which helped to distinguish the two genera. These included the size of the vertebral spines as well as the length of the sail from front to back. If you recall one of the first descriptions of Edaphosaurus we mentioned was that the sail continues up until the skull attaches to the neck whereas on Dimetrodon the sail ends at the point where the neck and body meet or right above the shoulders. These spines on Edaphosaurus also bear cross bars and are heavier than a Dimetrodon's, which adds to the inhibited speed of Edaphosaurus and may have potentially made the spine itself more delicate and cumbersome; which adds to the argument for herbivorous diet.
Edaphosaurus has been found all over the Southwest United States but has also been found in areas such as the Czech Republic and Slovakia. As one of the first large tetrapod herbivores it is very clear that it was successful all over the globe during its time.