Janiosteus is an extinct monospecific genus of placoderm arthrodire from the Middle Devonian: Late Givetian stage found in Timan, Russia.
| Janiosteus Temporal range: Middle Devonian: Givetian, | |
|---|---|
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 | |
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).[1] The phylogeny of Janiosteus within Panxiosteidae is shown in the cladogram below from the 2013 Zhu & Zhu study:[2]
| Eubrachythoraci |
|
Pachyosteomorphi | |||||||||||||||||||||||||||||||||
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:[3]
References
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