There is evidence for strong epaxial muscles along the base of the raised neural spines in both "Sphenacodon" and "Dimetrodon", likely helping to stiffen and strengthen the backbone for walking and for lunging at prey by restricting side-to-side flexing motion. A recent study of the structure of the neural spines on "Sphenacodon" confirms that the upper parts were not encased in a thick muscular hump and instead protruded above a layer of muscle to form a low dorsal crest. Finds of sphenacodontid specimens in which postmortem distortion of the body caused the dorsal spines to overlap suggests that the spines were not connected by hard or particularly tough tissue. The possible function of a low, skin-covered crest in "Sphenacodon" is debated. A thermoregulatory role seems unlikely, although the taller crest in "Sphenacodon ferocior" is allometrically larger than in "S. ferox". Recent research has favored a display role for the tall sails in "Dimetrodon" and "Edaphosaurus".