Ctenacanthus

{{Short description|Extinct genus of cartilaginous fishes}}

{{Automatic taxobox

| fossil_range = {{Fossil range| 363|323}}

| image = Ctenacanthus major Agassiz.png

| image_caption = Dorsal spine of the type species, C. major, as illustrated by Louis Agassiz

| image2 = Ctenacanthus concinnus.png

| image2_caption = Restoration of C. concinnus

| taxon = Ctenacanthus

| authority = Agassiz, 1837

| subdivision_ranks = Species

| subdivision = See text

| type_species = Ctenacanthus major

| type_species_authority = Agassiz, 1837

}}

File:Ctenacanthus concinnus body.png-age Cleveland Shale]]

Ctenacanthus (from {{langx|el|κτείς}} {{transl|el|kteis}}, 'comb' and {{langx|el|ἄκανθα}} {{transl|el|akantha}}, 'spine'){{cite book |last1=Roberts |first1=George |title=An etymological and explanatory dictionary of the terms and language of geology |date=1839 |publisher=Longman, Orme, Brown, Green, & Longmans |location=London |page=38 |url=https://archive.org/details/anetymologicala00robegoog |access-date=29 December 2021 |language=English}} is an extinct genus of ctenacanthiform chondrichthyan. Remains have been found in the Bloyd Formation (Carboniferous Period) of Arkansas and the Cleveland Shale (Devonian Period) of Ohio in the United States and in South America.Acanthodian fish remains from the Upper Silurian or Lower Devonian of the Amazon Basin, Brazil. Philippe Janvier, Jose Henrique G. Melo, Palaeontology, Aug 1988, Vol 31, part 3{{cite book|last1=Agassiz|first1=Louis|title=Contenant l'Histoire de l'Ordre de Placoïdes|date=1837|publisher=Petitpierre|location=Neuchâtel|pages=10–12|chapter-url=https://www.biodiversitylibrary.org/page/3725216|chapter=De genre Ctenacanthus Agass|series=Recherches sur les poissons fossiles|volume=3}}{{Cite web |title=Ctenacanthus |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=34489 |access-date=2023-04-25 |website=paleobiodb.org}}