Diplodoselachidae Dick, 1981

Johnson, Gary D. & Thayer, David W., 2009, Early Pennsylvanian xenacanth chondrichthyans from the Swisshelm Mountains, Arizona, USA, Acta Palaeontologica Polonica 54 (4), pp. 649-668 : 650

Family Diplodoselachidae Dick, 1981

Remarks.— Hampe’s (2003: 197) taxonomic review included five genera, including Orthacanthus , in this primitive family. Schneider and Zajíc (1994: 132) and Schneider (1996: 333– 334) also placed this genus in the diplodoselachids. Soler−Gijón (1997: 166) placed Orthacanthus in the Xenacanthidae based on occipital spine similarities to Xenacanthus and Triodus . Schultze and Soler−Gijón (2004) follow this assignment, but without comment. Rodrigo Soler−Gijón (personal communication, October 2007) further argued that Orthacanthus shares many features in occipital spine and postcranial morphology with Xenacanthus , Triodus , and Plicatodus , which are highly derived xenacanths. His point is well taken and may be correct that Orthacanthus should be in the Xenacanthidae .