''Thrinacodus'' is an extinct genus of basal

elasmobranch Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of g ...

, found worldwide from the Late Devonian-Lower Carboniferous. Most species are only known from their tricuspid teeth. ''T. gracia'', originally placed in the separate genus ''Thrinacoselache'' from the

Serpukhovian The Serpukhovian is in the ICS geologic timescale the uppermost stage or youngest age of the Mississippian, the lower subsystem of the Carboniferous. The Serpukhovian age lasted from Ma to Ma. It is preceded by the Visean and is followed b ...

-aged

Bear Gulch Limestone The Bear Gulch Limestone is a limestone-rich geological lens in central Montana, renowned for the quality of its late Mississippian-aged fossils. It is exposed over a number of outcrops northeast of the Big Snowy Mountains, and is often considere ...

, of what is now

Montana Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...

, is known from full body impressions, showing a long, slender eel-like body up to a metre in length, with an elongate rostrum. Stomach contents of ''T. gracia'' include remains of crustaceans and small

chondrichthyan Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue. C ...

fish ('' Harpagofututor'' and ''

Falcatus ''Falcatus'' is an extinct genus of falcatid chondrichthyan which lived during the early Carboniferous Period in Bear Gulch bay in what is now Montana. Description This fish was quite small, only getting to around 25–30 cm or 10-12 in ...

''). It is a member of the

Phoebodontiformes Phoebodontiformes is an extinct group of elasmobranchs, known from the Devonian and Carboniferous periods. It includes the genera ''Phoebodus'', '' Diademodus'' and '' Thrinacodus''. ''Phoebodus'' and ''Thrinacodus'' have slender, elongate bodie ...

References

Carboniferous sharks {{paleo-shark-stub Fossil taxa described in 1875