Helodus

{{Short description|Extinct cartilaginous fish genus}}

{{Distinguish|Henodus}}

{{Automatic taxobox

| image = Helodus simplex.jpg

| image_caption = Life reconstruction of Helodus simplex

| taxon = Helodus

| fossil_range = {{fossil range| Upper Devonian| Lower Permian| Upper Devonian-Lower Permian}}

| type_species = Helodus simplex

| type_species_authority = Agassiz, 1838

| authority = Agassiz, 1838

}}

File:Helodus sp.jpg

Helodus (from {{langx|el|ἧλος}} {{transliteration|el|helos}}, 'stud' and {{langx|el|ὀδούς}} {{transliteration|el|odoús}} 'tooth'){{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=76 |url=https://archive.org/details/anetymologicala00robegoog |access-date=30 December 2021 |language=English}} is an extinct genus of cartilaginous fish from the Upper Devonian through Lower Permian.Arno Hermann Müller: Textbook of paleozoology. Volume III, Vertebrates, Part 1. Gustav Fischer Verlag, 1985. While the type species, H. simplex from the Late Carboniferous (Moscovian ~ 315 million years ago{{Citation |last=Cohen |first=Karly E. |title=Teeth Outside the Jaw: Evolution and Development of the Toothed Head Clasper in Chimaeras |date=2025-04-05 |url=https://www.biorxiv.org/content/10.1101/2025.04.04.647311v1.full |access-date=2025-04-23 |publisher=bioRxiv |language=en |doi=10.1101/2025.04.04.647311 |last2=Coates |first2=Michael I. |last3=Fraser |first3=Gareth J.|url-access=subscription }}) of England is known from an articulated specimen, the rest of the species in this genus are known entirely from isolated teeth.Itano, W.M., Lambert, L.L. A new cochliodont anterior tooth plate from the Mississippian of Alabama (USA) having implications for the origin of tooth plates from tooth files. Zoological Lett 4, 12 (2018). {{doi|10.1186/s40851-018-0097-8|doi-access=free}} Over twenty species have been attributed to this genus, many of which may be anterior teeth of other cartilaginous fish. This makes Helodus a wastebasket taxon.{{Cite web|title=Extinct - complete list {{!}} Species {{!}} Shark-References|url=https://shark-references.com/species/listAllFossil/H|access-date=2020-11-29|website=shark-references.com}} For this reason, only the type species can be confidently attributed to this genus until articulated remains of other species are found. H. simplex was around 30 centimeters (1 foot) long.