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| Bataspis crux Meng, Ferrón, Pisani, Gai & Donoghue, 2026 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
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| 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.
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| 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]
