Xiangshuiosteus

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.[2]

Xiangshuiosteus
Temporal range: Early Devonian: Late Emsian,
Artist's reconstruction
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Placodermi
Order: Arthrodira
Suborder: Brachythoraci
Clade: Eubrachythoraci
Clade: Pachyosteomorphi
Superfamily: Dunkleosteoidea
Family: Dunkleosteidae
Genus: Xiangshuiosteus
Wang, 1992
Type species
Xiangshuiosteus wui
Wang, 1992

Etymology

The generic name literally translates as "Chinese: 香水; lit. 'perfume'(Pinyin:Xiāngshuǐ) + bone," but actually refers to Xiangshui Valley,[note 1] 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.[3]

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.[3]

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).[2] The cladogram below from the 2013 Zhu & Zhu study shows the placement of Xiangshuiosteus within Dunkleosteidae.[2]

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

Pachyosteomorphi

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:[4]

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

"Phlyctaenii"

See also

Notes

  1. Not to be confused with Xiangshui County (Chinese: 响水县; lit. 'noisy water')(Pinyin:Xiǎng shuǐ) in Jiangsu province

References

  1. Wang Junqing & Min, Zhu (1995). "Age of the Jiucheng Formation of Wuding,Yunnan". Institute of Vertebrate Palaeontology and Palaeoanthropology, Academia Sinica, Beijing. Retrieved 2013-05-20.
  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. Wang Junqing (April 1992). "NEW DISCOVERY OF EARLY MIDDLE DEVONIAN BRACHY-THORACID (PLACODERM FISH) FROM WUDING REGION OF YUNNAN". Vertebrata PalAsiatica. 30 (2): 111–119.
  4. 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.
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