Pachyosteomorphi

{{Automatic taxobox

| fossil_range = Devonian

| image = Dunkleosteus terrelli Cleveland Shales.jpg

| image_caption = Artist's reconstruction of various Cleveland Shale Pachyosteomorphi arthrodires, including Titanichthys (top), Selenosteus (eating a shark), adult and juvenile Dunkleosteus terrelli (center), and Gorgonichthys (bottom). From the Famennian stage of the Late Devonian.

| display_parents = 2

| taxon = Pachyosteomorphi

| authority = Stensiö, 1963

| subdivision_ranks = Sub-clades

| subdivision =

}}

Pachyosteomorphi is an extinct clade of arthrodire placoderms within the Eubrachythoraci (of the suborder Brachythoraci), armored fish most diverse during the Devonian. Most are considered to be pelagic (open ocean) long-distance swimmers, leading to their widespread distribution beginning from at least the Middle Devonian period.

Phylogeny

Pachyosteomorphi is the sister taxon to Coccosteomorphi, which together are the two main sub-clades of Eubrachythoraci. Pachyosteomorphi can be further sub-divided into Aspinothoracidi and Dunkleosteoidea,{{Cite journal |last1=Carr |first1=R.K. |last2=Hlavin |first2=W.J. |title=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) |journal=Zoological Journal of the Linnean Society |volume=159 |issue=1 |pages=195–222 |year=2010 |doi=10.1111/j.1096-3642.2009.00578.x |doi-access=free }}{{Cite journal |author1=You-An Zhu |author2=Min Zhu |title=A redescription of Kiangyousteus yohii (Arthrodira: Eubrachythoraci) from the Middle Devonian of China, with remarks on the systematics of the Eubrachythoraci | journal=Zoological Journal of the Linnean Society |volume=169 |issue=4 |pages=798–819 |year=2013 |doi=10.1111/zoj12089 |doi-access=free }} as shown in the cladogram below:{{Cite journal |last1=Zhu |first1=You-An |last2=Zhu |first2=Min |last3=Wang |first3=Jun-Qing |date=1 April 2016 |title=Redescription of Yinostius major (Arthrodira: Heterostiidae) from the Lower Devonian of China, and the interrelationships of Brachythoraci |journal=Zoological Journal of the Linnean Society |volume=176 |issue=4 |pages=806–834 |doi=10.1111/zoj.12356|issn=0024-4082 |doi-access=free }}