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| Foxaspis novemura Gai, Lin, Shan, Ferrón & Donoghue, 2023 |
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
