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 connected to Dimetrodon but did not share the same subfamily with Dimetrodon or Sphenacodon; it was a more primitive member of Sphenacodontidae. Ctenorhachis inhabited the Early Permian epoch. Two specimens, found in the Wichita Group outcropping areas of Baylor and Archer counties in north-central Texas, are known.