Stratigraphic chart of the lower Permian (partial)
Content updated October 16, 2005
DIMETRODON
Synapsida-Eupelycosauria-Sphenacodontidae
Above: picture of a sphenacodontid basioccipital-exoccipital (probably of a Dimetrodon) in lateral and posterior view. From Ryan Sandstone, Wellington Formation, near Waurika - Jefferson Co. Oklahoma. Lower Permian.
Abbreviations: bo, basioccipital process supporting ventral extension of the opistothic; cond, condyle; ex, exoccipital; np, notochordal pit; XII, foramen for the hypoglossal nerve.