Thrinacodus

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

{{Automatic taxobox

| fossil_range = Late Devonian-Lower Carboniferous {{fossilrange|Famennian|Serpukhovian}}

| image = Thrinacoselache gracia.jpg

| image_caption = Restoration of T. gracia

| image2 = Thrinacodus dziki.jpg

| image2_caption = Teeth of T. dziki

| taxon = Thrinacodus

| authority = St. John and Worthen, 1875

| subdivision_ranks = Species

| subdivision = *Thrinacodus bicuspidatus Ginter and Sun, 2007

• Thrinacodus dziki Ginter et al. 2014
• Thrinacodus ferox (Turner, 1982)
• Thrinacodus gracia (Grogan & Lund, 2008)
• Thrinacodus incurvus Newberry and Worthen, 1866
• Thrinacodus nanus St. John and Worthen, 1875
• Thrinacodus tranquillus Ginter, 2000

| synonyms = *Thrinacoselache Grogan & Lund, 2008

}}

Thrinacodus is an extinct genus of basal elasmobranch, found worldwide from the Late Devonian-Lower Carboniferous. The type species is Thrinacodus nanus.{{cite journal|author=Brett Roelofs, Milo Barham, Arthur J. Mory, Kate Trinajstics|date=January 2016|url=https://www.researchgate.net/publication/294795753|title=Late Devonian and Early Carboniferous chondrichthyans from the Fairfield Group, Canning Basin, Western Australia|journal=Palaeontologia Electronica|volume=19|issue=1|pages=1–28|doi=10.26879/583}} Most species are only known from their tricuspid teeth. T. gracia, originally placed in the separate genus Thrinacoselache from the Serpukhovian-aged Bear Gulch Limestone, of what is now Montana, is known from full body impressions, showing a long, slender eel-like body up to a metre in length, with an elongate rostrum.{{cite journal|last1=Grogan|first1=Eileen D.|last2=Lund|first2=Richard|title=A basal elasmobranch, Thrinacoselache gracia n. gen and sp., (Thrinacodontidae, new family) from the Bear Gulch Limestone, Serpukhovian of Montana, USA|journal=Journal of Vertebrate Paleontology|date=2008|volume=28|issue=4|pages=970–988|doi=10.1671/0272-4634-28.4.970|s2cid=84735866 }}{{Cite journal |last1=Ginter |first1=Michał |last2=Turner |first2=Susan |date=2010-12-02 |title=The middle Paleozoic Selachian genus Thrinacodus |url=https://doi.org/10.1080/02724634.2010.520785 |journal=Journal of Vertebrate Paleontology |volume=30 |issue=6 |pages=1666–1672 |doi=10.1080/02724634.2010.520785 |s2cid=86058786 |issn=0272-4634|url-access=subscription }}{{Cite journal |last1=Frey |first1=Linda |last2=Coates |first2=Michael |last3=Ginter |first3=Michał |last4=Hairapetian |first4=Vachik |last5=Rücklin |first5=Martin |last6=Jerjen |first6=Iwan |last7=Klug |first7=Christian |date=2019-10-09 |title=The early elasmobranch Phoebodus: phylogenetic relationships, ecomorphology and a new time-scale for shark evolution |journal=Proceedings of the Royal Society B: Biological Sciences |volume=286 |issue=1912 |pages=20191336 |doi=10.1098/rspb.2019.1336 |issn=0962-8452 |pmc=6790773 |pmid=31575362}} Stomach contents of T. gracia include remains of crustaceans and small chondrichthyan fish (Harpagofututor and Falcatus). It is a member of the Phoebodontiformes.