''Diplacanthus'' is an extinct genus of Mid to Late

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

fish in the class

Acanthodii Acanthodii or acanthodians is an extinct class of gnathostomes (jawed fishes). They are currently considered to represent a paraphyletic grade of various fish lineages basal to extant Chondrichthyes, which includes living sharks, rays, and ...

, known as spiny sharks.

Classification

The genus was named by

Louis Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he recei ...

in 1843. It was formerly regarded as belonging to the Climatiformes but recently reassigned to the

Diplacanthiformes Diplacanthiformes (also known as Diplacanthida, Diplacanthoidei, or Diplacanthini) is an order of "acanthodian" stem- chondrichthyans which lived during the Devonian Period. Subtaxa * ''incertae sedis'' ** Genus '' Bryantonchus'' ** Genus '' C ...

, in which it is united with, amongst others, ''Rhadinacanthu''s, '' Uraniacanthus'', and '' Culmacanthus''. Diplacanthiforms were widespread during the Middle and early

Late Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding ...

. They are best represented in the

Middle Devonian In the geological timescale, the Middle Devonian epoch (from 393.3 ± 1.2 million years ago to 382.7 ± 1.6 million years ago) occurred during the Devonian period, after the end of the Emsian age. The Middle Devonian epoch is subdivided into two ...

, by articulated fossils, fin spines, and abundant scales, the latter particularly from northern Europe. In a latest revision of the genus ''Diplacanthus,'' a large number of species from Europe were synonymized with earlier Scottish species, and these too were redefined. ''D. crassisimus'' was taken to have precedence over ''D. striatus'' as the name of the type specimen. ''Diplacanthus longispinus'' was reassigned to ''Rhadinacanthus longispinus'', within which were also included ''Diplacanthus horridus'' (Woodward, 1892) and ''Diplacanthus ellsi''. ''Diplacanthus tenuistriatus'' and ''Diplacanthus kleesmentae'' were however retained. Non-Laurussian species such as ''Diplacanthus acus'' from South Africa were not considered in this review.

Species

*†''D. acus'' Gess, 2001 *†''D. crassisimus'' Duff, 1842 (

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 ...

) *†''D. gravis?'' Valiukevičius, 1986 *†''D. kleesmentae?'' Valiukevičius, 1988 *†''D. poltnigi?'' Valiukevičius, 2003 *†''D. solidus?'' Valiukevičius, 1986 *†''D. tenuistriatus'' Traquair, 1844 ''Diplacanthus acus'' is described from a near complete whole-bodied impression discovered in 1999 during roadworks cutting the

Waterloo Farm lagerstätte The Waterloo Farm lagerstätte is a Famennian lagerstätte in South Africa that constitutes the only known record of a near-polar Devonian coastal ecosystem. History and discovery The Waterloo Farm Lagerstätte is an approximately 360 millio ...

in South Africa. The type specimen of ''Diplacanthus acus'' is approximately 100 mm long and has exceptionally long and thin ribbed spines. The intermediate spines are, conversely, extremely reduced. Unusually it preserves complete outlines of many of the fins. ''Diplacanthus'' is most commonly associated with deposits traditionally interpreted as fresh water. However, Waterloo Farm is interpreted as

estuarine An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

in origin, as is the Canadian Miguashaia lagerstätte from which two species of ''Diplacanthus'' have been described. The description of ''Diplacanthus acus'' provided the first record of a diplacanthid from the

Famennian The Famennian is the later of two faunal stages in the Late Devonian epoch. The most recent estimate for its duration is that it lasted from around 371.1 to 359.3 million years ago. An earlier 2012 estimate, still used by the International Commis ...

, with diplacanthids having previously been thought to have gone extinct by the end of the

Frasnian The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage. Major reef-building was under way during ...

.Janvier, P.(1996). Early Vertebrates. Oxford University Press, Oxford.

References

{{Taxonbar, from=Q3708872 Diplacanthiformes Middle Devonian cartilaginous fish Late Devonian cartilaginous fish Devonian cartilaginous fish of Africa Devonian cartilaginous fish of Europe Devonian cartilaginous fish of North America Fossil taxa described in 1843