A New Dayongaspid Galeaspid from the Silurian of the Lower Yangtze Region: Implications for Biogeography and the Evolution of Key Adaptations in Galeaspids

Abstract

Galeaspids are an extinct group of jawless armored fishes that are integral to understanding the origin of anatomical innovations of jawed vertebrates. Resolving the nature of the jawless ancestor of jawed vertebrates requires resolution of the anatomy of the earliest galeaspids, which is currently poorly known. Here we describe a new dayongaspid, Xihaiaspis wuningensis gen. et sp. nov., from the Early Telychian (Early Silurian) Qingshui Formation of Lixi Town, Wuning County, Jiujiang City, Jiangxi Province, China. This first report of dayongaspids from the Lower Yangtze region supports the relative proximity of, and faunal exchange between, South China and Tarim during the Early Telychian. It also informs on the monophyly of Dayongaspidae and the early branching position of this family within Galeaspida. In particular, Xihaiaspis wuningensis gen. et sp. nov. provides insights into the nature of the last common ancestor of Dayongaspiformes, Eugaleaspidiformes and Polybrachiaspiformes. These include the nature of the median dorsal opening, which was transversely oriented and slit-shaped, as well as on the presence of ventro-lateral fin-folds and dorsal spines, which were likely present in the ancestral galeaspid.

Keywords

Dayongaspidae / Galeaspida / Qingshui Formation / Silurian / Jiangxi Province

References

[1] Chen Y, Li Q, Zhou Z Det al.. A New Genus of Galeaspids (Jawless Stem- Gnathostomata) from the Early Silurian Chongqing Lagerstätte, China. Vertebrata PalAsiatica, 2024, 62(4): 245-261

[2] Donoghue P C J, Forey P L, Aldridge R J. Conodont Affinity and Chordate Phylogeny. Biological Reviews, 2000, 75(2): 191-251

[3] Gai Z K, Donoghue P C J, Zhu Met al.. Fossil Jawless Fish from China Foreshadows Early Jawed Vertebrate Anatomy. Nature, 2011, 476(7360): 324-327

[4] Gai Z K, Li Q, Ferrón H Get al.. Galeaspid Anatomy and the Origin of Vertebrate Paired Appendages. Nature, 2022, 609(7929): 959-963

[5] Gai Z K, Lin X H, Shan X Ret al.. Postcranial Disparity of Galeaspids and the Evolution of Swimming Speeds in Stem-Gnathostomes. National Science Review, 2023, 10(7): nwad050

[6] Gai Z K, Lu L W, Zhao W Jet al.. New Polybranchiaspiform Fishes (Agnatha: Galeaspida) from the Middle Palaeozoic of China and Their Ecomorphological Implications. PLoS One, 2018, 139e0202217

[7] Gai Z K, Zhu M. The Origin of the Vertebrate Jaw: Intersection between Developmental Biology-Based Model and Fossil Evidence. Chinese Science Bulletin, 2012, 57303819-3828

[8] Gai Z K, Zhu M. Evolutionary History of Agnathans and Their Fossil Records in China, 2017, Shanghai, Shanghai Scientific and Technical Publishers1314(in Chinese with English Abstract)

[9] Goloboff P A, Catalano S A. TNT Version 1.5, Including a Full Implementation of Phylogenetic Morphometrics. Cladistics, 2016, 32(3): 221-238

[10] Hughes C P, Ingham J K, Addison R. The Morphology, Classification and Evolution of the Trinucleidae (Trilobita). Philosophical Transactions of the Royal Society of London Series B, Biological Sciences, 1975, 272(920): 537-604

[11] Janvier P. La Structure de l’exosquelette des Galeaspida (Vertebrata). Comptes Rendus de l’Académie des Sciences. Série II. Mechanics. Physics. Chemistry. Space Sciences. Earth Sciences, 1990, 310(5): 655-659

[12] Janvier P, Thanh T D, Phuong T Het al.. Occurrence of Sanqiaspis, Liu, 1975 (Vertebrata, Galeaspida) in the Lower Devonian of Vietnam, with Remarks on the Anatomy and Systematics of the Sanqiaspididae. Comptes Rendus Palevol, 2009, 8(1): 59-65

[13] Janvier P, Tông-Dzuy T, Ta-Hoa P. A New Early Devonian Galeaspid from Bac Thai Province, Vietnam. Palaeontology, 1993, 36(2): 297-309

[14] Jiang W Y, Zhu M, Shi X Det al.. Qushiaspis, A New Genus of Gantarostrataspid Fish (Galeaspida, Stem-Gnathostomata) from the Lower Devonian of Yunnan, China. Historical Biology, 2021, 33(12): 3714-3722

[15] Keating J N, Donoghue P C J. Histology and Affinity of Anaspids, and the Early Evolution of the Vertebrate Dermal Skeleton. Proceedings Biological Sciences, 2016, 283(1826): 20152917

[16] Li X T, Zhang Y M, Lin X Het al.. New Findings of Changxingaspis (Xiushuiaspidae, Galeaspida) from the Silurian of Tarim Basin and Zhejiang Province, China. Acta Geologica Sinica - English Edition, 2024, 983531-540

[17] Lin X H, Zan C Y, Gai Z Ket al.. Deanaspis, A New Genus of Galeaspida (Jawless Stem Gnathostomata) from the Silurian of Jiangxi, China, and Its Evolutionary Implications. Journal of Systematic Palaeontology, 2025, 23(1): 2460479

[18] Liu Y H, Zhu M, Gai Z Ket al.. Zhu Met al.. Subclass Galeaspida. Palaeovertebrata Sinica, Volume I, Fishes, Fascile, Agnathans, 2015, Beijing, Science Press141-272(in Chinese)

[19] Liu Y H, Zhu M, Lin Xet al.. A Reappraisal of the Silurian Galeaspids (Stem-Gnathostomata) from Tarim Basin, Xinjiang. Vertebrata PalAsiatica, 2019, 57(4): 253-273(in Chinese with English Abstract)

[20] Liu Y L, Huang L B, Zong R Wet al.. New Material of Galeaspids from the Silurian Llandovery from Wuhan in South China. Earth Science, 2021, 46(9): 3307-3320(in Chinese with English Abstract)

[21] Liu Y L, Huang L B, Zong R Wet al.. The Oldest Eugaleaspiform (Galeaspida) from the Silurian Fentou Formation (Telychian, Llandovery) of Wuhan, South China. Journal of Systematic Palaeontology, 2021, 19(4): 253-264

[22] Liu Y L, Yin J Y, Fan R Yet al.. New Data on Silurian (Llandovery) Sinacanthids from Wuhan, South China and Their Biostratigraphic and Paleobiogeographic Implications. Palaeoworld, 2024, 33(5): 1242-1255

[23] Maddison W P, Maddison D R. Mesquite: A Modular System for Phylogenetic Workflows and Analyses, 2019[2025-12-30]

[24] Meng X Y, Gai Z K. Falxcornus, A New Genus of Tridensaspidae (Galeaspida, Stem-Gnathostomata) from the Lower Devonian in Qujing, Yunnan, China. Historical Biology, 2022, 34(5): 897-906

[25] Pan J, Wang S T. Xiushuiaspidae, A New family of Polybranchiaspformes from Xiushui of Jiangxi Province. Acta Palaeontologica Sinica, 1983, 22(5): 505-509(in Chinese with English Abstract)

[26] Pan J, Zeng X Y. Dayongaspidae, A New Family of Polybranchiaspiformes (Agnatha) from Early Silurian of Hunan, China. Vertebrata PalAsiatica, 1985, 23(3): 207-213(in Chinese with English Abstract)

[27] Rong J Y, Wang Y, Tang Pet al.. Age of the Silurian Tangchiawu, Kangshan and Jukeng Formations (with Marine Red Beds) in Eastern South China. Journal of Stratigraphy, 2023, 47(3): 237-267(in Chinese with English Abstract)

[28] Rong J Y, Wang Y, Zhan R Bet al.. Silurian Integrative Stratigraphy and Timescale of China. Science China Earth Sciences, 2019, 62(1): 89-111

[29] Sansom R S, Freedman K, Gabbott S Eet al.. Taphonomy and Affinity of an Enigmatic Silurian Vertebrate, Jamoytius kerwoodi White. Palaeontology, 2010, 53(6): 1393-1409

[30] Shan X R, Gai Z K, Lin X Het al.. The Oldest Eugaleaspiform Fishes from the Silurian Red Beds in Jiangxi, South China and Their Stratigraphic Significance. Journal of Asian Earth Sciences, 2022, 229: 105187

[31] Shan X R, Zhao W J, Lin X Het al.. The Correlations of the Lower Red Beds of Early Telychian (Llandovery, Silurian) in China from the Palaeoichthyological Evidence. Journal of Stratigraphy, 2022, 46(2): 138-153(in Chinese with English Abstract)

[32] Shan X R, Lin X H, Zhang Y Met al.. New Findings of Xiyuichthys (Xiushuiaspidae, Galeaspida) from the Silurian of Jiangxi Province and Tarim Basin. Vertebrata PalAsiatica, 2023, 61(4): 245-260

[33] Shan X R, Zhao W J, Gai Z K. A New Species of Jiangxialepis (Galeaspida) from the Lower Telychian (Silurian) of Jiangxi and Its Biostratigraphic Significance. Acta Geologica Sinica: English Edition, 2023, 97(2): 393-403

[34] Shan X R, Zhu M, Zhao W Jet al.. Fossil Fishes from the Silurian Lower Red Beds in Wuhan, Hubei and Their Biogeographic Significances. Journal of Palaegeography, 2023, 25(2): 327-340(in Chinese with English Abstract)

[35] Shan X R, Zhu M, Zhao W Jet al.. A New Genus of Sinogaleaspids (Galeaspida, Stem-Gnathostomata) from the Silurian Period in Jiangxi, China. PeerJ, 2020, 8: e9008

[36] Tarlo L H. Chapter 25 Agnatha. Geological Society, London, Special Publications, 1967, 2(1): 629-636

[37] Wang J Q, Wang N Z, Zhang G Ret al.. Agnathans from Llandovery (Silurian) of Kalpin, Xinjiang, China. Vertebrata PalAsiatica, 2002, 40(4): 245-256(in Chinese with English Abstract)

[38] Wang N Z. Notes on two genera of Middle Silurian Agnatha (Hanyangaspis and Latirostraspis) of China. Selected Papers of 13th and 14th Annual Conventions of the Paleontological Society of China, Hefei, 1986, Hefei, Anhui Sci Tech Publ House49-57(in Chinese with English Abstract)

[39] Wang N Z. Chang M M, Liu Y H, Zhang G R. Two New Silurian Galeaspids (Jawless Craniates) from Zhejiang Province, China, with A Discussion of Galeaspid-Gnathostome Relationships. Early Vertebrates and Related Problems of Evolutionary Biology, 1991, Beijing, Science Press4166

[40] Wang N Z, Donoghue P C J, Smith M Met al.. Histology of the Galeaspid Dermoskeleton and Endoskeleton, and the Origin and Early Evolution of the Vertebrate Cranial Endoskeleton. Journal of Vertebrate Paleontology, 2005, 25(4): 745-756

[41] Zhang Y M, Li X T, Shan X Ret al.. The First Galeaspid Fish (Stem-Gnathostomata) from the Silurian Xiushan Formation of Hunan Province, China. Historical Biology, 2024, 36(9): 1685-1696

[42] Zhao W J, Wang S T, Wang J Qet al.. The Subdivision and Correlation of the Silurian Fish-Bearing Strata and Caledonian Movement in Kalpin and Bachu regions, the Tarim Basin, Xinjiang. Journal of stratigraphy, 2009, 33(3): 225-240(in Chinese with English Abstract)

[43] Zhao W J, Zhu M. Siluro-Devonian Vertebrate Biostratigraphy and Biogeography of China. Palaeoworld, 2010, 19(1/2): 4-26

[44] Zhu M. Two New Eugaleaspids, with A Discussion on Eugaleaspid Phylogeny. Vertebrata PalAsiatica, 1992, 30(3): 169-184(in Chinese with English Abstract)

[45] Zhu M, Gai Z K. Phylogenetic Relationships of Galeaspids (Agnatha). Frontiers of Biology in China, 2007, 2(2): 151-169

[46] Zhu M, Janvier P. The Histological Structure of the Endoskeleton in Galeaspids (Galeaspida, Vertebrata). Journal of Vertebrate Paleontology, 1998, 18(3): 650-654

[47] Zong R W, Liu Y L. On the Age of Silurian Hanyangaspis-Sinacanthus Assemblage in Wuhan, Hubei Province. Journal of Stratigraphy, 2023, 47(3): 285-294(in Chinese with English Abstract)

[48] Zong R W, Liu Y L, Huang L Bet al.. Trilobites from the Silurian “Lower Red Beds” of Wuhan, South China: Stratigraphic and Paleogeographic Implications. Palaeoworld, 2022, 31(2): 239-248

[49] Zong R W, Liu Y L, Yin J Yet al.. Discovery of the Silurian Red Beds and Its Geological Significance in Wuhan Area, Eastern Hubei. South China Geology, 2022, 38(1): 110-119(in Chinese with English Abstract)

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