Biology:Xiangshuiosteus

Short description: Extinct genus of fishes

Xiangshuiosteus Temporal range: Early Devonian: Late Emsian, 393.3 Ma PreЄ Є O S D C P T J K Pg N ↓
Artist's reconstruction
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	†Placodermi
Order:	†Arthrodira
Suborder:	†Brachythoraci
Family:	†Dunkleosteidae
Genus:	†Xiangshuiosteus Wang, 1992
Type species
Xiangshuiosteus wui Wang, 1992

Xiangshuiosteus wui is an extinct monospecific genus of brachythoracid arthrodire placoderm from the Late Emsian stage of the Early Devonian epoch, discovered in Wuding County of Yunnan province, China . It has recently been reassessed as a dunkleosteid.

Etymology

The generic name literally translates as "Chinese: 香水; literally: 'perfume'(Pinyin:Xiāngshuǐ) + bone," but actually refers to Xiangshui Valley, the district in Wuding County where the holotype was found. The specific name honors Wu Baosheng, the gentleman who provided the holotype to Wang Junqing, the species' describer.

Specimen and taxonomy

X. wui is known from a flattened, "Buddhist cap" shaped skull roof. The skull roof is strongly reminiscent of those of coccosteids, but also has anatomical features otherwise diagnostic of buchanosteids. This mix of anatomy lead its describer, Wang Junqing, to suggest that X. wui is the sister taxon of Coccosteidae, and represents a transitional form between Coccosteidae and Buchanosteidae.

A 2013 reappraisal of Kiangyousteus and several other eubrachythoracid arthrodire genera by You-An Zhu and Min Zhu lead to the conclusion that X. wui not only does not represent a transitional form between coccosteids and buchanosteids, but is actually a dunkleosteid closely related to the Gogo Reef Eastmanosteus calliaspis (which is, in turn, implied to be not of the genus Eastmanosteus). The cladogram below from the 2013 Zhu & Zhu study shows the placement of Xiangshuiosteus within Dunkleosteidae.

Eubrachythoraci	Coccosteomorphi   Coccosteus cuspidatus       Harrytoombsia elegans       Mcnamaraspis kaprios   Incisoscutoidea   Compagopiscis croucheri       Incisoscutum ritchiei     Incisoscutum sarahae     Camuropiscidae   Latocamurus coulthardi     Camuropiscis laidlawi       Rolfosteus canningensis     Tubonasus lennardensis     Fallacosteus turneri               Aspinothoracidi   Dinichthys herzeri       Hadrosteus rapax       Gorgonichthys clarki       Heintzichthys gouldii   Selenosteidae   Stenosteus angustopectus       Gymnotrachelus hydei       Rhinosteus parvulus     Pachyosteus bulla                   Dunkleosteoidea   Westralichthys uwagedensis         Protitanichthys rockportensis   Panxiosteidae   Panxiosteus ocullus     Janiosteus timanicus     Plourdosteus canadensis       Dunkleosteidae     Eastmanosteus calliaspis     Xiangshuiosteus wui         Eastmanosteus pustulosus     Kiangyousteus yohii     Golshanichthys asiatica       Dunkleosteus amblyodoratus     Dunkleosteus terrelli     Dunkleosteus raveri

However, the subsequent 2016 Zhu et al. study using a larger morphological dataset recovered Xiangshuiosteus well outside of Dunkleosteoidea and even Eubrachythoraci, more in-line with Wang's original 1992 phylogenetic assessment of Xiangshuiosteus, as shown in the cladogram below:

Phlyctaenioidei	Elvaspis tuberculata     Dicksonosteus arcticus     Turrisaspis elektor     Groenlandaspis antarcticus     Holonema westolli   Brachythoraci Homostiidae   Homostius sulcatus     Antineosteus lehmani       Buchanosteoidea   Buchanosteus confertituberculatus     Goodradigbeeon australianum     Parabuchanosteus murrumbidgeeni         Dhanguura johnstoni       Gemuendenaspis angusta       Xiangshuiosteus wui   Eubrachythoraci Coccosteomorphi Coccosteoidea Coccosteidae     Millerosteus minor     Coccosteus cuspidatus         Dickosteus threiplandi     Watsonosteus fletti     Protitanichthys rockportensis       Panxiosteidae   Plourdosteus canadensis     Panxiosteus ocullus     Janiosteus timanicus       Incisoscutoidea   Harrytoombsia elegans       Torosteus tuberculatus     Torosteus pulchellus         Mcnamaraspis kaprios       Compagopiscis croucheri     Trematosteus fontanellus   Camuropiscidae     Incisoscutum ritchiei     Incisoscutum sarahae         Rolfosteus canningensis       Tubonasus lennardensis       Fallacosteus turneri       Camuropiscis laidlawi     Latocamurus coulthardi                     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

See also

• Jiuchengia a coccosteid found in the same formation.

References

Wikidata ☰ Q13402864 entry