Nassichuk, W.W. (1971)
Helicoprion and Physonemus, Permian vertebrates from the Assistence Formation, Canadian Arctic Archipelago. Geological Survey of Canada, Bulletin, 192, 83–93
Itano, W.M. & Houck, K.J. & Lockley, M.G. (2003)
Ctenacanthus and Other Chondrichthyan Spines and Denticles from the Minturn Formation (Pennsylvanian) of Colorado. Journal of Paleontology, 77(3), 524–535
DOI: 10.1666/0022-3360(2003)077<0524:CAOCSA>2.0.CO;2
Elliott, D.K. & Irmis, R.B. & Hansen, M.C. & Olson, T.J. (2004)
Chondrichthyans from the Pennsylvanian (Desmoinesian) Naco Formation of central Arizona. Journal of Vertebrate Paleontology, 24(2), 268–280
DOI: 10.1671/1978