Stratigraphic chart of the lower Permian (partial)
Content updated October 16, 2005
CTENOSPONDYLUS
Synapsida-Eupelycosauria-Sphenacodontidae
Above: picture in frontal view, of blade like neural spine of the same Ctenospondylus articulated lumbar vertebrae. From Lake Frederick - Tillman Co. Oklahoma. Lower Permian.