[PaleoIchthyology • 2021] Jiangxialepis retrospina • The Oldest eugaleaspiform (Galeaspida) from the Silurian Fentou Formation (Telychian, Llandovery) of Wuhan, South China

Jiangxialepis retrospina Liu, Huang, Zong & Gong, 2021; 

 interpretative drawings of A, Shuyu zhejiangensis Pan, 1986; B, Jiangxialepis retrospina gen. et sp. nov.; C, Meishanaspis lehmani Wang, 1991.

DOI: doi.org/10.1080/14772019.2021.1883755 

  Researchgate.net/publication/349934424

 Abstract

A new genus of Eugaleaspidiformes (Galeaspida, Agnatha), Jiangxialepis gen. nov., is described from the Llandovery (Silurian) Fentou Formation from Wuhan, Hubei, South China. The new genus belongs to the family Shuyuidae, as evidenced by the splayed posterior supraorbital canals, absence of ‘U’-shaped median dorsal canals, and three lateral transverse canals issuing from the infraorbital canals. The new genus possesses a middle dorsal spine, which is found in eugaleaspidiforms for the first time. Jiangxialepis differs from other genera of Shuyuidae based on the following characteristics: presence of a middle dorsal spine, the anterior end of the median dorsal opening slightly disrupting the rostral margin of the head shield, large oval orbital openings, pineal opening level with the centre of the orbital opening, and seven lateral transverse canals on each side. The new genus is the first discovery of a eugaleaspidiform in the Fentou Formation, which extends the age of eugaleaspiforms to the middle Telychian and illuminates the early morphological conditions of the Eugaleaspidiformes. Cladistic analysis shows that the new genus is the most primitive group of Eugaleaspidiformes (Shuyuidae) and forms a trichotomy with Shuyu and Meishanaspis. We interpret Jiangxialepis as a sub-demersal fish that lived in the brackish waters of an estuarine-deltaic environment.

 

Keywords: Jiangxialepis, Shuyuidae, Eugaleaspiformes, Fentou Formation, Silurian, Wuhan, South China

Photographs and interpretative drawing of Jiangxialepis retrospina gen. et sp. nov.
A, internal mould of a complete head shield, BGEG-JXD-07; B, external mould of a complete head shield, BGEG-JXD-06; C, external mould of an incomplete head shield, BGEG-JXD-01; D-F, interpretative drawings of A-C, respectively; G, external mould of an incomplete head shield, BGEG-JXD-04; H, interpretative drawing of G; I, synthetic restoration.

Abbreviations: c, corneal processes; dcm, dorsal commissure; ic, inner corneal processes; ldc, lateral dorsal canal; ifc, infraorbital canal; ltc a-c , a to c lateral transverse canal; ltc 1-4 , first to fourth lateral transverse canal; md.o, median dorsal opening; md.s, median dorsal spine; orb, orbital opening; pi, pineal opening; soc 2 , posterior supraorbital canal.

 Comparison of shuyuids. A, Shuyu zhejiangensis (Liu et al. 2015); B, Jiangxialepis retrospina gen. et sp. nov.; C, Meishanaspis lehmani (modified after Gai et al. 2005).

Jiangxialepis retrospina 

 

Reconstruction of the ecological environment for the middle Telychian galeaspids from Wuhan in South China.
1, Jiangxialepis; 2, Hanyangaspis; 3, algae; 4, lingulids; 5, eurypteri.

Yi-Long Liu, Lie-Bin Huang, Rui-Wen Zong and Yi-Ming Gong. 2021. The Oldest eugaleaspiform (Galeaspida) from the Silurian Fentou Formation (Telychian, Llandovery) of Wuhan, South China. Journal of Systematic Palaeontology. 19(4); 253-264. DOI: doi.org/10.1080/14772019.2021.1883755 

  Researchgate.net/publication/349934424_The_oldest_eugaleaspiform_Galeaspida_from_the_Silurian_Fentou_Formation_of_Wuhan_South_China

[PaleoIchthyology • 2024] Changxingaspis nianzhongi & C. gui • New Findings of Changxingaspis (Xiushuiaspidae: Galeaspida) from the Silurian of Tarim Basin and Zhejiang Province, China

 

Changxingaspis nianzhongi 

Li, Zhang, Lin, Zhu, Zhao, Tang, Shan & Gai, 2024

DOI: doi.org/10.1111/1755-6724.15168 

 Researchgate.net/publication/381715002

Abstract

New discovery of the early Silurian fossil fish Changxingaspis (Xiushuiaspidae, Galeaspida), Changxingaspis nianzhongi sp. nov. and C. gui, are described from the Tataertag Formation in Tarim Basin and the Kangshan Formation in Zhejiang Province, respectively. C. nianzhongi mainly differs from C. gui in the shape of the median dorsal opening that is transverse elliptic with a width/length ratio of about 3.0, the long lateral transverse canals extending to the lateral margin of the headshield, and the second lateral transverse canal with dichotomous branchings. Discovery of C. nianzhongi from the Tataertag Formation and C. gui from the Kangshan Formation provide direct evidence on the specific level for the correlation between these two formations, which further supports the Silurian fish-bearing red beds in northwest Zhejiang belonging to the Silurian Lower Red Beds (LRBs) rather than the Upper Red Beds (URBs). Additionally, as the first record of the Changxingaspis in Tarim Basin, it extends the paleogeographical distribution of this genus from the South China Block to the Tarim Block, providing new evidence to support faunal exchanges between these two blocks and the hypothesis of a united Tarim–South China Block during the early Silurian.

Keywords: vertebrate paleontology, Galeaspids, Changxingaspis, new taxon, Tataertag Formation, Kangshan Formation, Aeronian–Telychian, Tarim, Zhejiang

The paleogeographical distribution of Xiushuiaspidae on South China and Tarim blocks during the early Telychian, Llandovery, Silurian

(modified after Liu et al., 2023). 

Art credit: Yang Dinghua. 

Changxingaspis nianzhongi 

Xutong LI, Yumeng ZHANG, Xianghong LIN, Min ZHU, Wenjin ZHAO, Lizhou TANG, Xianren SHAN and Zhikun GAI. 2024. New Findings of Changxingaspis (Xiushuiaspidae, Galeaspida) from the Silurian of Tarim Basin and Zhejiang Province, China. Acta Geologica Sinica. 98(3); 531-540. DOI: doi.org/10.1111/1755-6724.15168

  Researchgate.net/publication/381715002_New_findings_of_Changxingaspis_from_the_Silurian_of_Tarim_Basin_and_Zhejiang_China

[PaleoIchthyology • 2023] Jiangxialepis rongi • The First Eugaleaspiforme Fish from the Silurian of the Tarim Basin reveals a close relationship between the Tarim and South China Blocks at 438 mya

Xiyuichthys zhangi [Xiushuiaspidae], Microphymaspis pani [Dayongaspidae], Platylomaspis serratus [Gumuaspidae], and
 Jiangxialepis rongi [Shuyuidae]  Liu, Shan, Lin, Shen, Liu, Zhang & Gai, 2023

DOI: doi.org/10.1016/j.palaeo.2023.111774

 

Highlights: 

• The first Eugaleaspiforme fish, Jiangxialepis rongi sp. nov., is established.

• The Tataertag Formation can be correlated with the Qingshui Formation.

• Shuyuidae provided key evidence for the correlation of Silurian LRBs in China.

• 5 dispersal events between South China and Tarim blocks were recognized.

• South China and Tarim blocks should be closely related at 438 mya.

Abstract

The first Eugaleaspiforme fish, Jiangxialepis rongi sp. nov., from the lower Telychian (Llandovery, Silurian) Tataertag Formation in the Tarim Basin is described and its palaeogeographic significance is evaluated. The new species can be assigned to the family Shuyuidae and distinguished from J. retrospina and J. jiujiangensis by its comparatively broader headshield, ornamentation, and serrated margin of the headshield and median dorsal opening. The discovery of J. rongi provides direct fossil evidence for the correlation of lower Telychian marine red beds between the Tarim Basin and South China and expands our knowledge of the distribution of Eugaleaspiforme fish into the Tarim Basin. An analysis of galeaspid paleogeographic distribution within a phylogenetic framework reveals at least five galeaspid dispersal events between the blocks of South China and the Tarim Basin during the early Telychian age. This indicates that the South China and Tarim blocks were close enough to share the same shallow marine environment, and perhaps comprise a united Tarim-South China Block during the early Silurian.

  

Keywords: Silurian, Galeaspid, Tarim, South China, Biogeography

Xiyuichthys zhangi [Xiushuiaspidae], Microphymaspis pani [Dayongaspidae], Platylomaspis serratus [Gumuaspidae], and Jiangxialepis rongi [Shuyuidae] 

 Jiangxialepis rongi sp. nov.

 

Wenyu Liu, Xianren Shan, Xianghong Lin, Yiming Shen, Yuhang Liu, Zehao Zhang and Zhikun Gai. 2023. The First Eugaleaspiforme Fish from the Silurian of the Tarim Basin reveals a close relationship between the Tarim and South China Blocks at 438 mya. Palaeogeography, Palaeoclimatology, Palaeoecology. 628; 111774. DOI: doi.org/10.1016/j.palaeo.2023.111774

[PaleoIchthyology • 2023] Jiangxialepis jiujiangensis • A New Species of Jiangxialepis (Galeaspida) from the Lower Telychian (Silurian) of Jiangxi, China and its Biostratigraphic Significance

 Jiangxialepis jiujiangensis 

Shan, Zhao & Gai, 2023

DOI: doi.org/10.1111/1755-6724.15009

 Researchgate.net/publication/364228998

Abstract

A new species of Shuyuidae (Eugaleaspiformes, Galeaspida), Jiangxialepis jiujiangensis sp. nov., is described from the lower Telychian (Llandovery, Silurian) Qingshui Formation in Jiujiang, Jiangxi Province, China. The new species differs from the type species J. retrospina from Wuhan, Hubei Province in its sharp and posteriorly positioned median dorsal spine and narrow spine-shaped inner cornual processes. The Silurian strata in Xiushui–Wuning area has provided a standard framework for the correlation of Silurian shallow marine red beds in South China. Thus, the finding of J. jiujiangensis from the Silurian Lower Red Beds (LRBs) in Jiangxi Province bears very important biostratigraphic significance. It can directly compare to Jiangxialepis retrospina from the Fentou Formation in Wuhan, Hubei Province in the genus level. This indicates that the age of the fish-bearing strata in Wuhan is most likely to be the early Telychian rather than middle Telychian as previously assumed.

Keywords: Galeaspids, Qingshui Formation, Lower Red Beds, Silurian, Jiangxi Province

Restoration of Jiangxialepis jiujiangensis sp. nov. and Jiangxialepis retrospina.

Art credit: Shi Aijuan.

Jiangxialepis jiujiangensis sp. nov.

Xianren Shan, Wenjin Zhao and Zhikun Gai. 2023. A New Species of Jiangxialepis (Galeaspida) from the Lower Telychian (Silurian) of Jiangxi and its Biostratigraphic Significance. Acta Geologica Sinica. DOI: doi.org/10.1111/1755-6724.15009

 Researchgate.net/publication/364228998_A_New_Species_of_Jiangxialepis_from_Silurian_of_Jiangxi

x.com/PDChina/status/1662658703215165442

https://news.sciencenet.cn/htmlpaper/2023/5/202351211301219581774.shtm

[PaleoIchthyology • 2024] Miaojiaaspis dichotomus • A New Genus of galeaspids (Eugaleaspiformes: Tujiaaspidae) from the early Silurian Chongqing Lagerstätte, China

 

Miaojiaaspis dichotomus 

Chen, Li, Zhou, Shan, Y.-A. Zhu, Wang, Wei & M. Zhu, 2024

 https://www.vertpala.ac.cn/EN/10.19615/j.cnki.2096-9899.240820 

 

The early Silurian Chongqing Lagerstätte (middle Telychian) yields exceptionally preserved articulated jawless and jawed fishes. Here, we describe a new eugaleaspiform (Galeaspida, jawless stem-Gnathostomata), Miaojiaaspis dichotomus gen. et sp. nov., from the Chongqing Lagerstätte in Xiushan, Chongqing, China. The new form resembles Tujiaaspis vividus in the short medial dorsal canal, and the presence of the branching ends of the lateral transverse canal. They differ in that T. vividus has highly developed subordinate branches of the sensory canals that form a reticulate sensory canal system, and the median dorsal opening is more elongated. Our phylogenetic analysis recovers M. dichotomus and T. vividus as a monophyletic clade (Tujiaaspidae fam. nov.), which is supported by two synapomorphies: the short medial dorsal canal, and the branching ends of the lateral transverse canal. Tujiaaspidae forms a trichotomy with Shuyuidae and a clade comprising Anjiaspis, Sinogaleaspidae, Yongdongaspidae, and the ‘eugaleaspid cluster’. The sensory canal patterns in galeaspids are compared to show the transformation sequence of the sensory canal system in Eugaleaspiformes.

Photographs (A, C) and interpretative drawings (B, D) of Miaojiaaspis dichotomus gen. et sp. nov. from Xiushan, Chongqing
A, B. an incomplete internal mold of the headshield with the trunk articulated, CIGMR V0125a; C, D. an incomplete external mold of the headshield with the trunk articulated, holotype, CIGMR V0125b

Subclass Galeaspida Tarlo, 1967

Order Eugaleaspiformes (Liu, 1965) Liu, 1980

Family Tujiaaspidae fam. nov.

Type genus Tujiaaspis Gai et al., 2022.

Referred genus Miaojiaaspis gen. nov.

Differential diagnosis Tujiaaspidae differs from other families of Eugaleaspiformes in the short medial dorsal canal, and the branching ends of the lateral transverse canal.

Remarks Our phylogenetic analysis shows that M. dichotomus and T. vividus form a monophyletic clade supported by two synapomorphies.

Genus Miaojiaaspis gen. nov.

Type species Miaojiaaspis dichotomus sp. nov.

Etymology From Miaojia, Pinyin for the Miao People, a minority ethnic group in China, which is one of the two main autonomous minority ethnic groups in Xiushan County, Chongqing, and aspis (Gr.), shield.

Differential diagnosis M. dichotomus differs from T. vividus in a more subtriangular headshield, no highly developed subordinate branches of sensory canals and a shorter median dorsal opening.

Miaojiaaspis dichotomus sp. nov.

Holotype An incomplete headshield with the trunk articulated, CIGMR V0125a, b (Figs. 2–3).

Referred specimens 8 complete headshields, CIGMR V0126–V0129, IVPP V28714–V28717 (Fig. 4).

Etymology From dichotomus (Latin), referring to the dichotomous ends of the lateral transverse canals.

Diagnosis Small-sized eugaleaspiform fish with a subtriangular headshield. Spine-shaped cornual and inner cornual processes caudo-laterally or caudally oriented. Longitudinal oval-like median dorsal opening. Pineal opening positioned behind the posterior margin of the orbits. Funnel-shaped supraorbital canals. Short medial dorsal canal. 

 

CHEN Yang, LI Qiang, ZHOU Zheng-Da, SHAN Xian-Ren, ZHU You-An, WANG Qian, WEI Guang-Biao, ZHU Min. 2024. A New Genus of galeaspids (jawless stem-Gnathostomata) from the early Silurian Chongqing Lagerstätte, China. Vertebrata Palasiatica. 62(4); 245-261.  DOI: 10.19615/j.cnki.2096-9899.240820 

 https://www.vertpala.ac.cn/EN/10.19615/j.cnki.2096-9899.240820 

[PaleoIchthyology • 2023] Foxaspis novemura • Postcranial Disparity of galeaspids (Galeaspida) and the Evolution of Swimming Speeds in Stem-gnathostomes

Foxaspis novemura

Gai, Lin, Shan, Ferrón & Donoghue, 2023

DOI: 10.1093/nsr/nwad050 

 Researchgate.net/publication/368895582

Abstract

Galeaspids are extinct jawless relatives of living jawed vertebrates whose contribution to understanding the evolutionary assembly of the gnathostome bodyplan has been limited by absence of postcranial remains. Here, we describe Foxaspis novemura gen. et sp. nov., based on complete articulated remains from a newly discovered Konservat-Lagerstätte in the Early Devonian (Pragian, ∼410 Ma) of Guangxi, South China. F. novemura had a broad, circular dorso-ventrally compressed headshield, slender trunk and strongly asymmetrical hypochordal tail fin comprised of nine ray-like scale-covered digitations. This tail morphology contrasts with the symmetrical hypochordal tail fin of Tujiaaspis vividus, evidencing disparity in galeaspid postcranial anatomy. Analysis of swimming speed reveals galeaspids as moderately fast swimmers, capable of achieving greater cruising swimming speeds than their more derived jawless and jawed relatives. Our analyses reject the hypothesis of a driven trend towards increasingly active food acquisition which has been invoked to characterize early vertebrate evolution.

Keywords: Galeaspida, jawed vertebrates, evolution, functional morphology, phylogenetics, modelling

Class Galeaspida Tarlo, 1967

Order Polybranchiaspidiformes Liu, 1965

Family Duyunolepididae P'an et Wang, 1978

Genus Foxaspis gen. nov.

Foxaspis novemura gen. et sp. nov.

 

Etymology. After the nine-tailed fox, a creature spoken of in the ancient Chinese mythological bestiary, the Shan-hai Ching (Classic of Mountains and Seas) which is a compilation of mythic geography and myth. Latin novem meaning nine; Latin -ura, meaning tail.

Holotype. A complete headshield articulated with body and tail V30958.1a,bpreserved together with a complete arthrodiran fish (Fig.1A,B).

Locality and horizon. Tongmu Town, Jinxiu County, Laibin City, Guangxi ZhuangAutonomous Region, China, the Xiaoshan Formation, Pragian, Early Devonian (Supplementary Fig. 1).

Zhikun Gai, Xianghong Lin, Xianren Shan, Humberto G. Ferrón and Philip C. J. Donoghue. 2023. Postcranial Disparity of galeaspids and the Evolution of Swimming Speeds in Stem-gnathostomes. National Science Review. nwad050. DOI: 10.1093/nsr/nwad050

  Researchgate.net/publication/368895582_Postcranial_disparity_of_galeaspids_and_the_evolution_of_swimming_speeds_in_stem-gnathostomes

[PaleoIchthyology • 2022] Falxcornus liui • A New Genus and Species of galeaspid (stem-Gnathostomata: Galeaspida: Tridensaspidae) from the Lower Devonian in Qujing, Yunnan, China

Falxcornus liui

Meng & Gai, 2022

 

DOI: 10.1080/08912963.2021.1952198

ABSTRACT

A new genus and species of galeaspid, Falxcornus liui gen. et sp. nov., is described from the Xishancun Formation (Lochkovian, Lower Devonian) in Qujing, Yunnan, China. The new taxon displays a suite of diagnostic characters of the Eugaleaspiformes and strikingly resembles the tridensaspids Tridensaspis and Pterogonaspis in its sickle-like complex of cornual and inner cornual processes, leaf-like inner cornual processes, and median dorsal opening posteriorly placed level with the centre of the orbital opening, but clearly differs from these genera in lacking the rostral process and laterally projecting cornual processes. An extended phylogenetic analysis of the Galeaspida suggests that Falxcornus, Pterogonaspis and Tridensaspis form a monophyletic group as the family Tridensaspidae, and Falxcornus is resolved as sister to Pterogonaspis and Tridensaspis. Therefore, Falxcornus liui gen. et sp. nov. now represents the most primitive and oldest known tridensaspid fish. Its subacute rostral margin and sickle-like complex of cornual and inner cornual processes likely represent an intermediate state of these highly specialised rostral and lateral projecting processes, respectively. The recurrent evolution of similar cephalic elaborations within the Galeaspida suggests that some galeaspids could manipulate water flow around their headshields to become active animals with higher manoeuvrability and versatility, similar to osteostracans.

KEYWORDS: Falxcornus, Lower Devonian, Galeaspida, Tridensaspidae, taxonomy, vertebrate palaeontology

Falxcornus liui gen. et sp. nov.

Xinyuan Meng and Zhikun Gai. 2022. Falxcornus, A New Genus of Tridensaspidae (Galeaspida, stem-Gnathostomata) from the Lower Devonian in Qujing, Yunnan, China. Historical Biology: An International Journal of Paleobiology. 34(5); 897-906. DOI: 10.1080/08912963.2021.1952198

[PaleoIchthyology • 2022] New Data on the Cranial Anatomy of Pterogonaspis (Galeaspida: Tridensaspidae) from the lower Devonian of Yunnan, China and its Evolutionary Implications

Pterogonaspis yuhaii (Zhu, 1992)

in Meng, Zhu, Li et Gai, 2022. 

DOI: 10.1002/ar.25098

 facebook.com/AnatomicalRecord 

Abstract

New material of the tridensaspid Pterogonaspis yuhaii is described from the Xujiachong Formation in Qujing City, Yunnan Province, revealing the morphology of the ventral side of the headshield for the first time. Most significantly, the cranial anatomy of Pterogonaspis provides the first fossil evidence for the position of the esophagus in galeaspids. The esophagus and dorsal aortae display a central placement in the postbranchial region and do not share a common canal as in osteostracans. Moreover, the paired and symmetrically extending dorsal aortae in galeaspids strikingly resemble those of jawed vertebrates, probably representing a plesiomorphic condition for vertebrates because they are also present in amphioxus and hagfishes. In contrast, the unpaired and asymmetrically extending dorsal aorta in osteostracans is similar to that of lampreys, probably resulting from convergent evolution. In addition, our new data also exhibit some characters that galeaspids uniquely share with osteostracans, such as the complete endoskeletal postbranchial wall and the extensive lateral expansion of the headshield with the marginal arteries and veins.

Keywords: dorsal aorta, esophagus, Pterogonaspis, Qujing, Yunnan

Life restoration of Pterogonaspis yuhaii.

Artwork: Dinghua Yang

SYSTEMATIC PALEONTOLOGY

Subclass Galeaspida Tarlo, 1967.

Order Eugaleaspiformes (Liu, 1965; Liu, 1980).

Family Tridensaspidae (Liu, 1986).

Genus Pterogonaspis (Zhu, 1992).

 

Pterogonaspis yuhaii  (Zhu, 1992)

Diagnosis (emended): The margin between the cornual process and the inner cornual process serrated; median dorsal opening fissure-shaped with length/width ≈ 10, calabash-shaped oralobranchial fenestra, six pairs of branchial fossae; ornamentation composed of minute granular tubercles, about 16 tubercles/mm2.

Locality and Horizon: Xujiachong Village, Qilin District, Qujing City, Yunnan Province, Xujiachong Formation, Cuifengshan Group, Pragian, Early Devonian.

Xin-Yuan Meng, Min Zhu, Qiang Li and Zhi-Kun Gai. 2022. New Data on the Cranial Anatomy of Pterogonaspis (Tridensaspidae, Galeaspida) from the lower Devonian of Yunnan, China and its Evolutionary Implications. The Anatomical Record. DOI: 10.1002/ar.25098

facebook.com/AnatomicalRecord/posts/549381357194732

   twitter.com/ChinaScience/status/1587673671786586112

[PaleoIchthyology • 2022] Tujiaaspis vividus • Galeaspid Anatomy and the Origin of Vertebrate Paired Appendages

Tujiaaspis vividus

Gai, Li, Ferrón, Keating, Wang, Donoghue & Zhu, 2022

DOI: 10.1038/s41586-022-04897-6

Abstract

Paired fins are a major innovation that evolved in the jawed vertebrate lineage after divergence from living jawless vertebrates. Extinct jawless armoured stem gnathostomes show a diversity of paired body-wall extensions, ranging from skeletal processes to simple flaps. By contrast, osteostracans (a sister group to jawed vertebrates) are interpreted to have the first true paired appendages in a pectoral position, with pelvic appendages evolving later in association with jaws. Here we show, on the basis of articulated remains of Tujiaaspis vividus from the Silurian period of China, that galeaspids (a sister group to both osteostracans and jawed vertebrates) possessed three unpaired dorsal fins, an approximately symmetrical hypochordal tail and a pair of continuous, branchial-to-caudal ventrolateral fins. The ventrolateral fins are similar to paired fin flaps in other stem gnathostomes, and specifically to the ventrolateral ridges of cephalaspid osteostracans that also possess differentiated pectoral fins. The ventrolateral fins are compatible with aspects of the fin-fold hypothesis for the origin of vertebrate paired appendages. Galeaspids have a precursor condition to osteostracans and jawed vertebrates in which paired fins arose initially as continuous pectoral–pelvic lateral fins that our computed fluid-dynamics experiments show passively generated lift. Only later in the stem lineage to osteostracans and jawed vertebrates did pectoral fins differentiate anteriorly. This later differentiation was followed by restriction of the remaining field of fin competence to a pelvic position, facilitating active propulsion and steering.

Systematic palaeontology

Class Galeaspida Tarlo, 1967

Order Eugaleaspidiformes Liu, 1980

Tujiaaspis vividus gen. et sp. nov.

Etymology. The genus name tujia, Pinyin for the Tujia people, a minority ethnic group in China, in reference to the two fossil sites located in Xiangxi Tujia, Miao Autonomous Prefecture, Hunan Province, and Xiushan Tujia, Miao Autonomous County, Chongqing Municipality; aspis (Gr.), shield; and species name vividus (L.), spirited, full of life.

Holotype. A nearly complete fish accessioned as Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) V26668 (Fig. 1).

 

Zhikun Gai, Qiang Li, Humberto G. Ferrón, Joseph N. Keating, Junqing Wang, Philip C. J. Donoghue and Min Zhu. 2022.  Galeaspid Anatomy and the Origin of Vertebrate Paired Appendages. Nature. 609, 959–963. DOI: 10.1038/s41586-022-04897-6

bristol.ac.uk/biology/news/2022/dead-fish-breathes-new-life-into-the-evolutionary-origin-of-fins-and-limbs.html

[PaleoIchthyology • 2020] Rumporostralis gen. nov. • A New Genus of Sinogaleaspids (stem-Gnathostomata: Galeaspida) from the Silurian Period in Jiangxi, China

Rumporostralis xikengensis (Pan & Wang, 1980)

in Shan, Zhu, Zhao, et al., 2020

 DOI: 10.7717/peerj.9008

Artwork: Xiaocong Guo.

Abstract

Galeaspids are an endemic clade of jawless stem-gnathostomes known as ostracoderms. Their existence illuminates how specific characteristics developed in jawed vertebrates. Sinogaleaspids are of particular interest among the galeaspids but their monophyly is controversial because little is known about Sinogaleaspis xikengensis. Newly discovered sinogaleaspids from the Lower Silurian of Jiangxi, China provide a wealth of data and diagnostic features used to establish the new genus, Rumporostralis gen. nov., for Sinogaleaspis xikengensis. A morphological study showed that the sensory canal system of sinogaleaspids had mosaic features similar to those of three known galeaspids. There are 3–8 pairs of transverse canals in the Sinogaleaspidae, which suggests that the sensory canal system of galeaspid probably had a grid distribution with transverse canals arranged throughout the cephalic division. Phylogenetic analysis of Galeaspida supports the monophyly of the Sinogaleaspidae, consisting of Sinogaleaspis, Rumporostralis, and Anjiaspis. However, Shuyu and Meishanaspis form another monophyletic group, Shuyuidae fam. nov., which is outside all other eugaleaspidiforms. We propose a cladistically-based classification of Galeaspida based on our analysis.

Systematic paleontology

Subclass Galeaspida Tarlo, 1967
Order Eugaleaspiformes (Liu, 1965) Liu, 1980

Family Shuyuidae fam. nov.

Differential diagnosis. Shuyuidae differs from other families of Eugaleaspiformes in the splayed posterior supraorbital canals and absence of U-shaped median dorsal canals.

Type genus. Shuyu Gai et al., 2011

Referred genera. Meishanaspis

Remarks. Newly discovered sinogaleaspid material provides a wealth of data and reliable diagnostic features to erect the new genus Rumporostralis gen. nov. for ‘Sinogaleaspis’ xikengensis. Our phylogenetic analysis of Galeaspida shows that Shuyu and Meishanaspis are not included in Sinogaleaspidae and form another monophyletic group. A new family, Shuyuidae fam. nov., was created for Shuyu and Meishanaspis. Shuyuidae is positioned in the new cladogram as the sister to all other Eugaleaspididiformes with synapomorphies including a subtriangular head-shield and longitudinal oval or wedge-shaped median dorsal opening.


Family Sinogaleaspidae Pan & Wang, 1980

Differential diagnosis. Sinogaleaspidae differs from other families of Eugaleaspiformes in the V-shaped posterior supraorbital canals and more than 2 pairs of median transverse canals (autapomorphy).

Type genus. Sinogaleaspis. Pan & Wang, 1980

Referred genera. Rumporostralis gen. nov., Anjiaspis

Remarks. The amended Sinogaleaspidae, including Sinogaleaspis shankouensis, Rumporostralis xikengensis, (Figs. 3, 4) R. shipanensis (Fig. 5), and Anjiaspis reticularis is monophyletic with synapomorphy (U-shaped median dorsal canals) and autapomorphy (more than 2 pairs of median transverse canals).


Genus Rumporostralis gen. nov.

Etymology. Rumpo latin, state of being dehiscent or split; rostralis, Latin, snout, in referring to the rostral margin of the head-shield split by the anterior end of median dorsal opening.

Type species. Rumporostralis xikengensis (Pan & Wang, 1980)

Referred species. Rumporostralis shipanensis gen. et sp. nov.

Differential diagnosis. Rumporostralis differs from other Eugaleaspiformes by an unclosed rostral margin of the head-shield, indicating autapomorphy.

Remarks. The genus including R. xikengensis and R. shipanensis is uniquely characterized by the unclosed rostral margin.

Holotype. A nearly complete head-shield GMC V1753A, B

Referred specimens. A nearly complete head-shield IVPP V25136.1, three incomplete head-shields IVPP V25136.2–4.

Type locality and horizon. Xikeng village and Shipan reservoir, Taiyangsheng Town, Xiushui County, Jiangxi Province, China; Xikeng formation, Telychian, Llandovery, Silurian.

Differential diagnosis. R. xikengensis differs from the other species R. shipanensis in the small size of the head-shield.

Rumporostralis shipanensis gen. et sp. nov.

Holotype. An incomplete head-shield IVPP V26114.1a, b

Type locality and horizon. Shipan reservoir, Taiyangsheng Town, Xiushui County, Jiangxi Province, China; Xikeng formation, Telychian, Llandovery, Silurian.

Differential diagnosis. R. shipanensis differs from the type species R. xikengensis by the large size of the head-shield.

Figure 7: Life restoration of Sinogaleaspis shankouensis (left) and Rumporostralis xikengensis (right) in a fresh river.

Artwork: Xiaocong Guo.

Conclusion: 

The newly discovered sinogaleaspids from the Lower Silurian in Jiangxi, China provides a wealth of new data and reliable diagnostic features to assign the new genus, Rumporostralis gen. nov., to ‘Sinogaleaspis’ xikengensis. This in-depth morphological study determined that the sensory canal system of sinogaleaspids exhibits the mosaic features of three known galeaspid patterns. The presence of 3-8 pairs of transverse canals in Sinogaleaspidae suggests that the sensory canal system of galeaspids probably displayed a grid distribution with transverse canals arranged throughout the cephalic division. An extended phylogenetic analysis of Galeaspida corroborates the monophyly of Sinogaleaspidae, which consists of Sinogaleaspis, Rumporostralis, and Anjiaspis. Shuyu and Meishanaspis were excluded from Sinogaleaspidae to form the monophyletic group Shuyuidae fam. nov., which is the sister of all other Eugaleaspididiformes. We propose a cladistically-based classification of the Galeaspida.

Xianren Shan, Min Zhu, Wenjin Zhao, Zhaohui Pan, Pingli Wang and Zhikun Gai. 2020. A New Genus of Sinogaleaspids (Galeaspida, stem-Gnathostomata) from the Silurian Period in Jiangxi, China.  PeerJ. 8:e9008. DOI: 10.7717/peerj.9008

[PaleoIchthyology • 2015] A Streamlined Jawless Fish (Galeapida) from the Lower Devonian of Yunnan, China and Its Taxonomic and Paleoecological Implications

Rhegmaspis xiphoidea  Gai, Zhu, Jia & Zhao, 2015 

B. Rhegmaspis xiphoidea with streamlined body, which is more suggestive of a superbenthic habitat

Fig. 2 Photograph of a complete head-shield of Rhegmaspis xiphoidea gen. et sp. nov. (IVPP V 19354.1A, holotype)

Fig. 5 Restoration of Rhegmaspis xiphoidea gen. et sp. nov.

Abstract   

A new genus and species of the Huananaspiformes (Galeaspida), Rhegmaspis xiphoidea, is described from the Posongchong Formation (Pragian, Early Devonian), Zhaotong, Yunnan Province, China. The new taxon is characterized by having a torpedo-shaped head-shield, a long rostral process, ventrolaterally set orbits, and ventrally curved branchial fossae, but no corners, inner corners, and ventral rim of head-shield. It is assigned to the family Gantarostrataspidae that include Gantarostrataspis and Wumengshanaspis. According to the new material and new observation, the Gantarostrataspidae is emended and a fresh look is prososed for Gantarostrataspis and Wumengshanaspis. As a streamlined jawless fish, Rhegmaspis displays an adaptation for a suprabenthic lifestyle with more active feeding behavior among galeaspids. The new form not only enriches the diversity of the Huananaspiformes, but also provides evidence for the last adaptive radiation of galeaspids by occupying an unexploited ecological niche during the Pragian of the Early Devonian.

Key words   Zhaotong, Yunnan; Lower Devonian; Galeaspida, Huananaspiformes; taxonomy; paleoecology

Rhegmaspis xiphoidea  Gai, Zhu, Jia & Zhao, 2015
B. Rhegmaspis xiphoidea with streamlined body, which is more suggestive of a superbenthic habitat;
B1. a streamlined body can minimize water pressure drag largely when swimming;
B2. a cross section of the head-shield, showing the ventrally curved branchial fossae and absence of ventral rim.

Abbreviations: bra.c. brain cavity; br.f. branchial fossae; obr.c. oralobrachial chamber; vr. ventral rim.

Fig. 2 Photograph of a complete head-shield of Rhegmaspis xiphoidea gen. et sp. nov. (IVPP V 19354.1A, holotype) 

Fig. 5 Restoration of Rhegmaspis xiphoidea gen. et sp. nov.

A. dorsal view; B. ventral view; C. lateral view. 

Abbreviations: br.f. branchial fossa; md.o. median dorsal opening; obr.f. oralobrachial fenestra; orb. orbital opening; pi. pineal fossa; ro. rostral process; soc2. posterior supraorbital canal; m. mouth.

Systematic paleontology

Subclass: Galeaspida Tarlo, 1967

Supraorder: Polybranchiaspidida Janvier, 1996

Order: Huananaspiformes Janvier, 1975

Family: Gantarostrataspidae Wang & Wang, 1992

Genus: Rhegmaspis gen. nov.

Type species: Rhegmaspis xiphoidea sp. nov.

Etymology: Rhegma, Greek, rupture, breach; aspis Greek, shield.

Rhegmaspis xiphoidea sp. nov.

(Figs. 2−6, 9E, 10B, cover image)

Etymology: Xiphoideus (swordlike).

Holotype: A complete head-shield (IVPP V 19354.1A, B).

Paratype: A nearly complete head-shield (IVPP V 19354.2), an incomplete head-shield (V 19354.4), an incomplete endocast of skull (V 19354.3).

Horizon and type locality: Early Devonian, Pragian, Posongchong Formation,

Zhaotong, Yunnan, China.

Fig. 10 The lifestyle of galeaspids in benthic (A) and superbenthic (B) habitats
A. ‘Dongfangaspis’ qujingensis with a flattened head-shield, which is suggestive of a benthic habitat; A1. a flattened head-shield bears much water pressure drag when swimming, but permit remaining on the bottom without a significant energetic cost; A2. a cross section of the head-shield, showing the transversely elongated branchial fossae and ventral rim;
B. Rhegmaspis xiphoidea with streamlined body, which is more suggestive of a superbenthic habitat; B1. a streamlined body can minimize water pressure drag largely when swimming; B2. a cross section of the head-shield, showing the ventrally curved branchial fossae and absence of ventral rim.

Abbreviations: bra.c. brain cavity; br.f. branchial fossae; obr.c. oralobrachial chamber; vr. ventral rim.

GAI Zhi-Kun, ZHU Min, JIA Lian-Tao and ZHAO Wen-Jin. 2015. A Streamlined Jawless Fish (Galeapida) from the Lower Devonian of Yunnan, China and Its Taxonomic and Paleoecological Implications. VERTEBRATA PALASIATICA. 53(2); 93-109. 

http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/201504/t20150420_4341614.html

http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/201504/P020150420387565261949.pdf

ResearchGate.net/publication/279806349_A_streamlined_jawless_fish_(Galeapida)_from_the_Lower_Devonian_of_Yunnan_China_and_its_taxonomic_and_paleoecological_implications

New jawless fish found from the Lower Devonian of Yunnan, China

http://phy.so/360919467 via @physorg_com