Dinichthys

Not to be confused with Dinictis.

Dinichthys (from Greek: δεινός deinós, 'terrible' and Greek: ἰχθύς ichthys 'fish') is an extinct monospecific genus of large marine arthrodire placoderm from the Late Devonian (Famennian stage) measuring around 3 metres (9.8 ft) long.^[1] Fossils were recovered from the Ohio Shale Formation along the Olentangy River in Delaware County, Ohio.

Dinichthys Temporal range: Late Devonian: Famennian, 371.1–359.3 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	†Placodermi
Order:	†Arthrodira
Clade:	†Phlyctaenioidei
Suborder:	†Brachythoraci
Clade:	†Eubrachythoraci
Clade:	†Pachyosteomorphi
Clade:	†Aspinothoracidi
Genus:	†Dinichthys Newberry, 1868
Species
Dinichthys herzeri Newberry, 1868 (type)
Synonyms
Ponerichthys Miller, 1892

Classification History

Life restoration

Dinichthys was originally described in 1868 by John Newberry on the basis of an incomplete skull roof and mandibles (holotype AMNH 81). Subsequently, many unrelated large arthrodires were originally classified together within this genus, including species now assigned to Dunkleosteus, Eastmanosteus, and Titanichthys. Notably, the type species of Dunkleosteus was originally described as Dinichthys terrelli by Newberry in 1873, and was later separated into Dunkleosteus by Jean-Pierre Lehman in 1956. Dunkleosteus was still thought to be closely related to Dinichthys, and they were grouped together in the family Dinichthyidae. However, in the 2010 Carr & Hlavin phylogenetic study, Dunkleosteus and Dinichthys were found to belong to two separate clades. Carr & Hlavin resurrected the family Dunkleosteidae and placed Dunkleosteus, Eastmanosteus, and a few other genera from Dinichthyidae within it.^[2] Dinichthyidae, in turn, is left a monospecific family^[3] and dismissed as a family grouping,^[4] and the genus Dinichthys is now considered a monotypic genus, containing only the type species, D. herzeri.^[2]

Phylogeny

Dinichthys is a member of the clade Aspinothoracidi, which belongs to the clade Pachyosteomorphi, one of the two major clades within Eubrachythoraci. The cladogram below shows the phylogeny of Dinichthys:^[5]

Eubrachythoraci

Coccosteomorphi  Pachyosteomorphi  Rhachiosteus pterygiatus Dunkleosteoidea  Eastmanosteus calliaspis Eastmanosteus pustulosus Kiangyousteus yohii Golshanichthys asiatica Westralichthys uwagedensis Dunkleosteus raveri Dunkleosteus terrelli Dunkleosteus amblyodoratus  Heterostiidae  Heterosteus ingens Yinosteus major Aspinothoracidi Tapinosteus heintzi Bullerichthys fascidens Kendrickichthys cavernosus Bruntonichthys multidens Dinichthys herzeri Hadrosteus rapax Gorgonichthys clarki  Selenosteidae  Heintzichthys gouldii Pachyosteus bulla Gymnotrachelus hydei Stenosteus angustopectus Brachyosteus dietrichi Melanosteus occitanus Rhinosteus parvulus

References

1. Bashford Dean (1895). Fishes, Living and Fossil: An Outline of Their Forms and Probable Relationships. Macmillan and Company. p. 130. Retrieved 28 August 2022.
2. Carr, R.K.; Hlavin, W.J. (2010). "Two new species of Dunkleosteus Lehman, 1956, from the Ohio Shale Formation (USA, Famennian) and the Kettle Point Formation (Canada, Upper Devonian), and a cladistic analysis of the Eubrachythoraci (Placodermi, Arthrodira)". Zoological Journal of the Linnean Society. 159 (1): 195–222. doi:10.1111/j.1096-3642.2009.00578.x.
3. Carr, Robert K.; William J. Hlavin (2 September 1995). "Dinichthyidae (Placodermi):A paleontological fiction?". Geobios. 28: 85–87. Bibcode:1995Geobi..28...85C. doi:10.1016/S0016-6995(95)80092-1.
4. You-An Zhu; Min Zhu (2013). "A redescription of Kiangyousteus yohii (Arthrodira: Eubrachythoraci) from the Middle Devonian of China, with remarks on the systematics of the Eubrachythoraci". Zoological Journal of the Linnean Society. 169 (4): 798–819. doi:10.1111/zoj12089.
5. Zhu, You-An; Zhu, Min; Wang, Jun-Qing (1 April 2016). "Redescription of Yinostius major (Arthrodira: Heterostiidae) from the Lower Devonian of China, and the interrelationships of Brachythoraci". Zoological Journal of the Linnean Society. 176 (4): 806–834. doi:10.1111/zoj.12356. ISSN 0024-4082.