Stereophallodon is an extinct genus of non-mammalian synapsids.
See also List of pelycosaurs
References
The main groups of non-mammalian synapsids at Mikko's Phylogeny Archive
Bibliography A. S. Romer. 1937. New genera and species of pelycosaurian reptiles. Proceedings of the New England Zoölogical Club 16:89-95 Brinkman, D. & Eberth, D.A., 1986, The anatomy and relationships of Stereophallodon and Baldwinonus (Reptilia, Pelycosauria): Breviora, no. 485, p. 34.