[PaleoIchthyology • 2026] Bataspis crux • A galeaspid (jawless stem gnathostome) from the Lochkovian of Yunnan with a batwing-shaped head adapted for hydrodynamic efficiency

 

Bataspis crux

Meng, Ferrón, Pisani, Gai & Donoghue, 2026 

 DOI: doi.org/10.1111/pala.70081

Life restoration by Dinghua Yang.

Abstract

Galeaspids are an extinct group of jawless fishes from the Silurian–Devonian of China and northern Vietnam that are key to understanding the origin of vertebrate anatomical innovations. A new eugaleaspid, Bataspis crux gen. et sp. nov., is described based on fossil material from the Lochkovian (Early Devonian) Xishancun Formation of Qujing, Yunnan, China. Bataspis crux possesses a suite of unusual features, especially its bat-wing-like cornual processes that are seamlessly integrated with a brim-like rostral margin without a rostral process, constituting a unique morphology for galeaspids. Maximum parsimony, maximum likelihood and Bayesian phylogenetic inference all support membership in the family Tridensaspidae. We employed computational fluid dynamics to infer the hydrodynamic properties of the headshield of B. crux. Our analysis reveals that this species achieves an exceptionally high lift-to-drag ratio; the highest recorded among known galeaspids. This remarkable efficiency stems from its low drag across various angles of attack, coupled with passive lift generation through the exploitation of the Bernoulli effect by the airfoil cross-section of the cornual processes. This suggests that the species was an effective gliding cruiser, outperforming not only galeaspids but also other stem gnathostomes, such as osteostracans and pteraspidomorphs. These results provide new insights into our understanding of the evolution of Tridensaspidae, the ecological habits of stem gnathostomes and convergence in the evolutionary assembly of the gnathostome bodyplan.

Keywords: galeaspid, phylogenetic analysis, hydrodynamic analysis, lift-to-drag ratio, convergence, morphological function

Bataspis crux, holotype, IVPP V30969: A, internal mould in dorsal view; B, external mould in ventral view.

Abbreviations: c, cornual process; dcm, dorsal commissure; ic, inner cornual process; ifc, infraorbital canal; ldc, lateral dorsal canal; ltc, lateral transverse canal; mdc, median dorsal canal; md.o, median dorsal opening; orb, orbital opening; pi, pineal opening; se, serrated edge; soc2, posterior supraorbital canal; v.mtc, vestige of the median transverse canal; vr, ventral rim.

 All scale bars represent 1 cm.

SYSTEMATIC PALAEONTOLOGY

Subphylum VERTEBRATA-CRANIATA Linnaeus 1758

Infraphylum GNATHOSTOMATA Cope 1889

Subclass GALEASPIDA Tarlo 1967

Order EUGALEASPIFORMES (Liu 1965) Liu 1980

Family TRIDENSASPIDAE Liu 1986

Genus Bataspis nov.

 

Derivation of name: Bat from English, the shape of the cornual processes of Bataspis is similar to the membranous wings in bats.

Type species: Bataspis crux sp. nov.

Differential diagnosis: Bataspis is assigned to Eugaleaspiformes because it exhibits a suite of diagnostic features in morphology: subtriangular headshield with cornual and inner cornual processes, slit-like median dorsal opening, and typical eugaleaspid-type sensory canals. Although Bataspis lacks a rostral angle or process, its diagnostic specialized laterally-projecting processes suggest it differs from the members of Shuyuidae, Sinogaleaspidae, and Eugaleaspidae and can be assigned to Tridensaspidae. Compared with other members of Tridensaspidae, the absence of the rostral angle and the presence of vestiges of the median transverse canal distinguish Bataspis and Falxcornus; the lack of the rostral process constitute a diagnostic difference between Bataspis and the sister group including Pterogonaspis and Tridensaspis. Additionally, Bataspis contains serrations along with the margin connecting the cornual and inner cornual processes and the lateral margins of the median dorsal opening that differ from Falxcornus.

Bataspis crux sp. nov.

 

Derivation of name: The verb ‘to cruise’, in the sense of ‘to move from one side to the other’, is derived (via Norse and Old English) from the Latin crux (cross).

Holotype: A nearly complete headshield and its counterpart, IVPP V30969 (Fig. 1A–B).

Locality & horizon: Near the Qujing Maternal and Child Health Care Hospital Qilin District, Qujing City, Yunnan Province, Xishancun Formation, Cuifengshan Group, Lochkovian, Early Devonian.

Diagnosis: Medium-sized tridensaspid fish; subtriangular headshield; arcuate rostral margin without rostral angle and process; cornual process spine-like, projecting posterolaterally; lobular inner cornual process projecting posteriorly, slightly stronger than cornual process; the angle between the cornual and inner cornual processes exceeding 90° (sickle-like); margin of the headshield connecting the cornual and inner cornual processes serrated; median dorsal opening slit-like (length/width >6) with nearly parallel lateral serrated margins, the posterior margin almost level with the centra of the orbital openings, and its middle part convex forward; orbital opening large, round, and dorsally positioned; pineal opening small, round, beyond the posterior margin of the orbital opening; sensory canal system typical eugaleaspid-type, with three pairs of lateral transverse canals and vestiges of the median transverse canal.

Artistic life restoration of Bataspis crux.

Artwork by Dinghua Yang.

CONCLUSION: 

We describe Bataspis crux, a new species of galeaspid from Xishancun Formation in the Early Devonian (Lochkovian age) of Yunnan, China. Our phylogenetic analyses ally the new genus to the family Tridensaspidae, sister to the clade of Pterogonaspis and Tridensaspis, and sharing with Falxcornus the status as the oldest known tridensaspids. The results of probabilistic phylogenetic methods indicate that more data are needed to clarify the phylogenetic relationships of galeaspids such as the family Shuyuidae. Bataspis crux extends beyond the range of phenotypic variation known previously for galeaspids. The unique morphological features of this bat-like jawless fish result in a high lift-to-drag ratio when at low angles of attack. Our results reveal the breadth of locomotor capabilities available to galeaspids and other jawless stem-gnathostomes, demonstrating that an absence of flexible paired fins was not an impediment to ecological diversity.

Xinyuan Meng, Humberto G. Ferrón, Davide Pisani, Zhikun Gai and Philip C. J. Donoghue. 2026. Bataspis crux, a galeaspid (jawless stem gnathostome) from the Lochkovian of Yunnan with a batwing-shaped head adapted for hydrodynamic efficiency. Palaeontology.  DOI: doi.org/10.1111/pala.70081 [04 August 2026]

[PaleoIchthyology • 2026] Asioaspis brachyotus • A New Genus of Polybranchiaspiformes (Galeaspida: stem-Gnathostomes) from the Lower Devonian of Yunnan, China

 

Asioaspis brachyotus

 R.-R. Zhang, N. Zhang, Li, Zhu & Gai, 2026

 

VERTEBRATA ALASIATICA. 64(2);   

 

A new genus and species, Asioaspis brachyotus gen. et sp. nov. of Polybranchiaspiformes, is described from the Lower Devonian Lochkovian Xishancun Formation near Miandian Reservoir, Qujing City, Yunnan Province, China. The new genus is characterized by an elongated ovoid headshield with serrated lateral margins, a small subcircular median dorsal opening, short and laterally projecting cornual processes, an exceptionally broad ventral rim, 12 pairs of branchial fossae, and coarse granular tubercles (~3/mm²). It displays a mosaic of characters of the most primitive polybranchiaspiform (Platylomaspis), derived Polybranchiaspiformes, and even the basal members of the galeaspid family Dayongaspidae. Phylogenetic analysis resolves A. brachyotus as an intermediate taxon between the most primitive Gumuaspidae and other derived Polybranchiaspiformes. Although A. brachyotus also shares the broad ham-brim-like ventral rim with the Gumuaspidae, its other characters are more like other derived Polybranchiaspiformes. In particular, its median dorsal opening and paired orbital openings are not highly close-set on the top of the headshield as in the Gumuaspidae, but rather significantly separated from each other and close to the margin of the ventral rim as in the Pentathyraspidae, Duyunolepididae, and Polybranchiaspidae. These proportions indicate that it was unlikely to have lived a semi-infaunal lifestyle and are more consistent with the epibenthic habit typical of most galeaspids, representing an evolutionary transition from the semi-infaunal benthic to epibenthic lifestyle within Polybranchiaspiformes.

Photograph of Asioaspis brachyotus gen. et sp. nov. from Lower Devonian Xishancun Formation, Qujing, Yunnan in ventral view
A. an incomplete headshield, paratype, IVPP V26676. 2; B. a nearly complete dorsal headshield, holotype, V26676. 1
A. an incomplete dorsal headshield, IVPP V26676.5; B. an incomplete dorsal headshield, V26676.4b

Subclass Galeaspida Tarlo, 1967 

Supraorder Polybranchiaspidida Janvier, 1996 

Order Polybranchiaspiformes Liu, 1965 

Family Asioaspidae fam. nov. 

Type genus Asioaspis gen. nov. 

Differential diagnosis: The Asioaspidae is distinguished from other families of Polybranchiaspiformes by its short, ear-like, and laterally projecting cornual processes. It resembles the Gumuaspidae in having a broad ventral rim, but differs in lacking a rostral process. It differs from the Duyunolepididae, Pentathyraspidae, and Polybranchiaspidae by the presence of a broad ventral rim and further differs from the Duyunolepididae by bearing a pair of broad inner cornual processes. Therefore, a new family, the Asioaspidae fam. nov., is herein established.

Genus Asioaspis gen. nov.  

Type species Asioaspis brachyotus gen. et sp. nov. 

Etymology: Asioaspis is derived from Asio (referring to owls of the genus Asio characterized by prominent ear tufts) plus aspis (Greek shield). 

Diagnosis: Medium-sized polybranchiaspiform characterized by an ovoid headshield with serrated lateral margins; the rostral margin arcuate, but lacking a rostral process; the cornual processes short and projecting laterally; the inner cornual processes large and broad leaf-shaped; median dorsal opening small and subcircular in shape; orbital opening large, round, and dorsally positioned; the sensory canals are well developed, V-shaped posterior supraorbitals and four pairs of lateral transverse canals issuing from the lateral dorsal canal; ventral rim of headshield remarkably broad, 13.5–14.1 mm in width on each side (approximately one half of the width of the entire headshield); a large dome-shaped oralobranchial chamber (a composite chamber with both oral and branchial functions) with 12 pairs of branchial fossae; and ornamentation consists of coarse tubercles (~3/mm²)

 Asioaspis brachyotus gen. et sp. nov. 

Etymology: The brachyotus means short-eared, which is in reference to its short and laterally projecting cornual processes that resemble a pair of short ears on the headshield, as in Asio.

Type locality and horizon: Miandian Reservoir in the Triathlon Sports Park, Qilin District, Qujing City, Yunnan Province, China; Xishancun Formation, lower Lochkovian, Lower Devonian.

Morphological comparison of Polybranchiaspiformes, Dayongaspidida, and Huananaspidiformes

A. Asioaspis; B. Dayongaspis (Zhang et al., 2024); C. Foxaspis (Gai et al., 2023); D. Platylomaspis (redrawn after Gai et al., 2018); E. Rhegmaspis (Gai et al., 2015); F. Rhegmaspis (Gai et al., 2015); G. Nanningaspis (redrawn after Gai et al., 2018)

A–E, G. in dorsal views; F. in ventral view.  

Phylogenetic diagram of Dayongaspidida, Polybranchiaspiformes, and Huananaspidiformes
Dayongaspis (Zhang et al., 2024); Platylomaspis (redrawn after Gai et al., 2018); Nanningaspis (redrawn after Gai et al., 2018); Polybranchiaspis (Liu, 1965); Foxaspis (Gai et al., 2023); Rhegmaspis (Gai et al., 2015).

No scaled

 Life restoration of Asioaspis brachyotus gen. et sp. nov. 

ZHANG Rui-Rui, ZHANG Ning, LI Qiang, ZHU Min and GAI Zhi-Kun. 2026. Asioaspis, A New Genus of Polybranchiaspiformes (Galeaspida, stem-Gnathostomes) from the Lower Devonian of Yunnan, China.  VERTEBRATA PALASIATICA. 64(2); 137-150.  DOI: 10.19615/j.cnki.2096-9899.260113 [20 April 2026] 

https://www.vertpala.ac.cn/EN/10.19615/j.cnki.2096-9899.260113

[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

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   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