Ctenacanthiformes
Ctenacanthiformes is an extinct order of cartilaginous fish. They possessed ornamented fin spines at the front of their dorsal fins and cladodont-type dentition, that is typically of a grasping morphology, though some taxa developed cutting and gouging tooth morphologies. Some ctenacanths are thought to have reached sizes comparable to the great white shark, with body lengths of up to and weights of, while others reached lengths of only. The earliest ctenacanths appeared during the Frasnian stage of the Late Devonian, with the group reaching their greatest diversity during the Early Carboniferous, and continued to exist into at least the Middle Permian. Some authors have suggested members of the family Ctenacanthidae may have survived into the Cretaceous based on teeth found in deep water deposits of Valanginian age in France and Austria, however, other authors contend that the similarity of these teeth to Paleozoic ctenacanths is only superficial, and they likely belong to neoselachians instead.
Taxonomy
Ctenacanthiformes are suggested to be more closely related to living elasmobranchs than to Holocephali, though less closely than euselachians like hybodonts. The monophyly of the Ctenacanthiformes has been questioned, with some studies recovering the group as a whole as paraphyletic or polyphyletic with respect to other groups of total group elasmobranchs like Xenacanthiformes.Following Hodnett et al. 2024
Ctenacanthidae Dean 1909
- Ctenacanthus Agassiz, 1837
- Cladodoides Maisey, 2001
- Cladodus Agassiz, 1843
- Goodrichthys Moy-Thomas, 1951
- Troglocladodus Hodnett et al. 2024
- Avonacanthus Maisey 2010
- Bythiacanthus St. John and Worthen 1875
- Dracopristis Hodnett et al. 2021
- Glencartius Ginter and Skompski 2019
- Glikmanius Ginter et al. 2005
- Heslerodus Ginter 2002
- Heslerodoides Ivanov 2022
- Kaibabvenator Hodnett et al. 2012
- Nanoskalme Hodnett et al. 2012
- Tamiobatis Eastman, 1897
- Saivodus Duffin & Ginter, 2006
- Neosaivodus Hodnett et al. 2012