''Acanthorhachis'' is an enigmatic extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of chondrichthyan from the

Carboniferous period The Carboniferous ( ) is a geologic period and system of the Paleozoic era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the Permian Period, Ma. It is the fifth and penultimate perio ...

. Its name is derived from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

word ''acanthos'' meaning "spine" and the Greek suffix for spine, -''rhachis''. This is due to the spine-like

dermal denticles A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as w ...

and their subsidiary spines, which coated the exterior of the animal. The authors who erected this genus suggested the common name "The Spiny Spined Shark." The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

''Listracanthus spinatus'' was in 1896 named by Herbert Bolton. It is closely related to '' Listracanthus''. It differs from it in the size, structure, and distribution of dermal spines. It is currently monotypic, containing only the species ''A. spinatus''. This shark is thus far only described from the British Isles. ''Acanthorhachis'' was first described from the Westphalian-aged lower coal measures of Yorkshire, England. It occurs rarely in

Viséan The Visean, Viséan or Visian is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the second stage of the Mississippian, the lower subsystem of the Carboniferous. The Visean lasted from to Ma. It follows ...

-aged Eyam Limestone of Derbyshire, England.

References

Carboniferous cartilaginous fish Carboniferous fish of Europe Monotypic prehistoric cartilaginous fish genera Fossil taxa described in 2013 {{Paleo-cartilaginous-fish-stub