Ctenorhachis was related to Dimetrodon, but did not belong to the same subfamily as Dimetrodon and Sphenacodon, being a more basal member of Sphenacodontidae. Ctenorhachis lived in the Early Permian epoch. Two specimens are known that have been found from the Wichita Group outcropping in Baylor and Archer counties, north-central Texas.
Ctenorhachis was associated with Dimetrodon, but did not belong to the same subfamily as Dimetrodon and Sphenacodon, being a more primitive member of Sphenacodontidae. Ctenorhachis lived during the Early Permian epoch. Two known specimens have been discovered from the Wichita Group in outcropping areas of Baylor and Archer counties, north-central Texas.