They possessed ornamented fin spines at the front of their dorsal fins and cladodont-type dentition,[1] that is typically of a grasping morphology, though some taxa developed cutting and gouging tooth morphologies.

[2] Some ctenacanths are thought to have reached sizes comparable to the great white shark, with body lengths of up to 7 metres (23 ft) and weights of 1,500–2,500 kilograms (3,300–5,500 lb),[3] while others reached lengths of only 30 centimetres (12 in).

[4] The earliest ctenacanths appeared during the Frasnian stage of the Late Devonian (~383-372 million years ago), with the group reaching their greatest diversity during the Early Carboniferous (Mississippian), and continued to exist into at least the Middle Permian (Guadalupian).

[4] 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[5] and Austria,[6] however, other authors contend that the similarity of these teeth to Paleozoic ctenacanths is only superficial, and they likely belong to neoselachians instead.

[9] Following Hodnett et al. 2024[4] Ctenacanthidae Dean 1909 Heslerodidae Maisey 2010 "Saivodus group"