Abstract
The armoured ankylosaurian dinosaurs are best known from Late Cretaceous Northern Hemisphere ecosystems, but their early evolution in the Early–Middle Jurassic is shrouded in mystery due to a poor fossil record1,2. Spicomellus afer was suggested to be the world’s oldest ankylosaur and the first from Africa, but was based on only a single partial rib from the Middle Jurassic of Morocco3. Here we describe a new, much more complete specimen that confirms the ankylosaurian affinities of Spicomellus, and demonstrates that it has uniquely elaborate dermal armour unlike that of any other vertebrate, extant or extinct. The presence of ‘handle’ vertebrae in the tail of Spicomellus indicates that it possessed a tail weapon, overturning current understanding of tail club evolution in ankylosaurs, as these structures were previously thought to have evolved only in the Early Cretaceous4. This ornate armour may have functioned for display as well as defence, and a later reduction to simpler armour with less extravagant osteoderms in Late Cretaceous taxa might indicate a shift towards a primarily defensive function, perhaps in response to increased predation pressures or a switch to combative courtship displays.
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Data availability
All data, code and the phylogenetic matrix are available in the Supplementary Information.
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Acknowledgements
Our team’s work is funded by the British Institute of Libyan and Northern African Studies, the Natural History Museum’s Science Investment Fund and the University of Birmingham’s International Science Partnerships Fund. The life reconstruction in Fig. 2 and the Extended Data Fig. 1 was produced by M. Dempsey for this publication. TNT was made available by the Willi Hennig Society. S.C.R.M. thanks K. Acheson-Dumbravă, P. Andrews and J. Craig for advice and support with this project. This paper is a contribution to the Natural History Museum’s Evolution of Life Research Theme.
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S.C.R.M., R.J.B. and D.O. conceived the project. Funding was acquired by S.C.R.M. and R.J.B.; S.C.R.M., R.J.B., D.O., K.E.-c., A.O., K.B., A.E.K., L.E.M., D.C.W., S.W. and M.S. excavated the specimen. D.O., K.E.-c., A.O., K.B., A.P., S.C.R.M. and R.J.B. prepared, conserved and curated the specimen. S.C.R.M., R.J.B., A.O., K.E.-c. and P.M.B. wrote the manuscript. All of the authors read, commented on and approved the submitted version.
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Extended data figures and tables
Extended Data Fig. 1 A life reconstruction of Spicomellus afer by Matthew Dempsey.
One cervical half-ring with elongate spikes, small spikes covering the dorsum of the body and large spikes and a sacral shield over the hips are in their known positions on the body; the location of all other armour, and the presence of spikes at the end of the tail, is conjectural.
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Supplementary Sections 1–5, including Supplementary Figs. 1–13 and additional references.
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Maidment, S.C.R., Ouarhache, D., Ech-charay, K. et al. Extreme armour in the world’s oldest ankylosaur. Nature (2025). https://doi.org/10.1038/s41586-025-09453-6
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DOI: https://doi.org/10.1038/s41586-025-09453-6
