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Janiosteus Temporal range: Middle Devonian: Givetian, 387.7–382.7 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
Suborder:	†Brachythoraci
Family:	†Panxiosteidae
Genus:	†Janiosteus Ivanov, 1988
Type species
Janiosteus timanicus Ivanov, 1989

Janiosteus is an extinct monospecific genus of placoderm arthrodire from the Middle Devonian: Late Givetian stage found in Timan, Russia.

Phylogeny

Janiosteus is a member of Panxiosteidae. In the 2010 Carr & Hlavin phylogenetic study, Panxiosteidae was recognized as the sister taxon to the family Dunkleosteidae, which together comprised the superfamily Dunkleosteoidea (one of the three major clades of Eubrachythoraci). The phylogeny of Janiosteus within Panxiosteidae is shown in the cladogram below from the 2013 Zhu & Zhu study:

However, the subsequent 2016 Zhu et al. study using a larger morphological dataset recovered Panxiosteidae well outside of Dunkleosteoidea, instead within Coccosteomorphi and then Coccosteoidea as the sister group of Coccosteidae, as shown in the cladogram below:

References

1. 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.
2. 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.
3. 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.

v t e Arthrodira
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Infraphylum: Gnathostomata Class: "Placodermi" Gnathostomata see Gnathostomata Placodermi see Placodermi Arthrodira see below↓
Arthrodira Arthrodira Aethaspis Aleosteus Anarthraspis Antarctaspis Baringaspis Bryantolepis Erikaspis Eskimaspis Heightingtonaspis Kujdanowiaspis Lataspis Lehmanosteus Mediaspis Proaethaspis Qataraspis Sigaspis Simblaspis Yujiangolepis Wuttagoonaspidae Wuttagoonaspis Yiminaspis Phyllolepida Gavinaspis Phyllolepididae Austrophyllolepis Cobandrahlepis Cowralepis Phyllolepis Placolepis Yurammia Actinolepidae Actinolepis Ailuracantha Bollandaspis Szelepis Phlyctaenioidei Dicksonosteus Phlyctaeniidae Aggeraspis Arctaspis Barwickosteus Cartieraspis Diadsomaspis Elegantaspis Gaspeaspis Grifftaylor Heterogaspis Huginaspis Kolpaspis Kueichowlepis Lyhoalepis Neophlyctaenius Pageauaspis Phlyctaenius Prosphymaspis Stipatosteus Arctolepididae Arctolepis Heintzosteus Huginaspis? Kueichowlepis? Groenlandaspididae Africanaspis Boomeraspis Cosmacanthus Groenlandaspis Mithakaspis Mulgaspis Tiaraspis Turrisaspis Williamsaspididae Elvaspis Williamsaspis Brachythoraci Antineosteus Dhanguura? Gemuendenaspis Maideria Xiangshuiosteus? Holonematidae Artesonema Belemnacanthus Bimbianga Deirosteus Deveonema Gyroplacosteus Holonema Megaloplax Rhenonema Tropidosteus Tropinema Homostiidae Angarichthys Cathlesichthys Dhanguura? Euleptaspis Euleptaspis Luetkeichthys Migmatocephala Antineosteus Atlantidosteus Homosteus Tityosteus Buchanosteidae Arenipiscis Buchanosteus Burrinjucosteus Errolosteus Exutaspis Goodradigbeeon Narrominaspis Parabuchanosteus Toombsosteus Taemasosteus Uralosteus Eubrachythoraci see below↓
Eubrachythoraci Coccosteomorphi Coccosteoidea Coccosteidae Belgiosteus Clarkeosteus Coccosteus Dickosteus Jiuchengia Livosteus Millerosteus Protitanichthys Watsonosteus Panxiosteidae Janiosteus Kimberleyichthys? Panxiosteus Plourdosteus? Incisoscutoidea Belosteus? Compagopiscis Cyrtosteus? Harrytoombsia? Mcnamaraspis? Parabelosteus? Torosteus Trematosteus Camuropiscidae Camuropiscis Fallacosteus Incisoscutum Latocamurus Rolfosteus Tubonasus Pachyosteomorphi Leptosteus Rhachiosteus Dunkleosteoidea Dunkleosteus Eastmanosteus Golshanichthys Hussakofia Kiangyousteus Westralichthys Xiangshuiosteus? Heterosteidae Herasmius Heterosteus Yinostius Aspinothoracidi Bruntonichthys Bullerichthys Bungartius Dinichthys Dinomylostoma Erromenosteus Hadrosteus Holdenius Kendrickichthys Mylostoma Squamatognathus Tafilalichthys Tapinosteus Titanichthys Brachydeiridae Brachydeirus Oxyosteus Synauchenia Selenosteidae Alienacanthus Amazichthys Brachyosteus Braunosteus Draconichthys Enseosteus Gorgonichthys Gymnotrachelus Heintzichthys Melanosteus Microsteus Pachyosteus Paramylostoma Phymosteus Rhinosteus Selenosteus Stenosteus Walterosteus

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