"Dimetrodon limbatus" was first described by Edward Drinker Cope in 1877 as "Clepsydrops limbatus". (The name "Clepsydrops" was first coined by Cope in 1875 for sphenacodontid remains from Vermilion County, Illinois, and was later employed for many sphenacontid specimens from Texas; many new species of sphenacodontids from Texas were assigned to either "Clepsydrops" or "Dimetrodon" in the late nineteenth and early twentieth centuries.) Based on a specimen from the Red Beds of Texas, it was the first known sail-backed synapsid. In 1940, paleontologists Alfred Romer and Llewellyn Ivor Price reassigned "C. limbatus" to the genus "Dimetrodon", making "D. limbatus" the type species of "Dimetrodon".