Huttenlocker, A.K.; Rega, E.; Sumida, S.S. (2010). “Comparative anatomy and osteohistology of hyperelongate neural spines in the sphenacodontids Sphenacodon and Dimetrodon (Amniota: Synapsida)”. Journal of Morphology271 (12): 1407–1421. doi:10.1002/jmor.10876. PMID20886514.
Huttenlocker, A.K.; Rega, E.; Sumida, S.S. (2010). “Comparative anatomy and osteohistology of hyperelongate neural spines in the sphenacodontids Sphenacodon and Dimetrodon (Amniota: Synapsida)”. Journal of Morphology271 (12): 1407–1421. doi:10.1002/jmor.10876. PMID20886514.