# The diversity of Irish Late Devonian plants: new insights from the permineralized flora of the Hook Peninsula (County Wexford)

Thibault Durieux, Anne-Laure Decombeix, Chris Mays, Cyrille Prestianni, Merlin Ramel, Gaëlle Viennois, Carla J Harper

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Thibault Durieux, Anne-Laure Decombeix, Chris Mays, Cyrille Prestianni, Merlin Ramel, et al. The diversity of Irish Late Devonian plants: new insights from the permineralized flora of the Hook Peninsula (County Wexford). 9. Agora Paleobotanica Meeting, Agora Paleobotanica, Jul 2025, Paris, France. **hal-05184135**

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https://hal.inrae.fr/hal-05184135v1

Submitted on 24 Jul 2025

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# The diversity of Irish Late Devonian plants: new insights from the permineralized flora of the Hook Peninsula (County Wexford)

Thibault DURIEUX<fnref n="1" />*, Anne-Laure DECOMBEIX<fnref n="2" />, Chris MAYS<fnref n="3" />,<fnref n="4" />, Cyrille PRESTIANNI<fnref n="5" />, Merlin RAMEL<fnref n="2" />, Gaelle VIENNOIS<fnref n="2" />, Carla J. HARPER<fnref n="1" />.

At the end of the Devonian, marine organisms experienced a major biological crisis, however, the impact of this event on plant diversity remains under debate <fnref n="1" />,<fnref n="2" /> and additional information on the taxonomical and anatomical diversity of Late Devonian and early Carboniferous floras is needed to better address this question. Localities with fossil plants from these intervals are rare, especially those with anatomically preserved specimens, but the Hook Peninsula in Ireland is one of the few places in the world where such fossils occur. This area, first studied by Matten in the 80s <fnref n="3" />,<fnref n="4" />, has been reinvestigated recently by our team, providing new information on the early woody tree *Archaeopteris/Callixylon*, with the description of a new species <fnref n="5" /> and a report of its ability to produce tyloses against pathogens or embolism ⁶. This presentation will review these discoveries and present ongoing work on specimens from the Hook Peninsula, including: (1) the description of a putative new species of progymnosperm, (2) the discovery of a small lycopsid bisporangiate cone that may belong to *Wexfordia hookense* <fnref n="3" />, and (3) the identification of a new locality with anatomically preserved seed-plants. Most specimens have been studied using the thin-section technique, however, a subset of specimens (n = 6) was also imaged using high-flux X-ray computed tomography at Synchrotron SOLEIL (Paris). Combined with photogrammetric imaging of large and/or fragile specimens in the field, this allowed us to overcome some limits of classical methods for studying anatomically preserved plants. Altogether, this work provides a better view of the Irish Late Devonian floral diversity and new data to analyse the impacts of the end-Devonian biological crisis on the vegetation.

1. Marshall, J. E. A., J. Lakin, I. Troth, and S. M. Wallace-Johnson. 2020. UV-B radiation was the Devonian-Carboniferous boundary terrestrial extinction kill mechanism. *Sciences Advances* 6: eI80018.

2. Capel, E., C. J. Cleal, P. Gerrenienne, T. Servais, and B. Cascales-Miñana. 2021. A factor analysis approach to modelling the early diversification of terrestrial vegetation. *Palaeogeography, Palaeoclimatology, Palaeoecology* 566: 110170.

3. Matten, L. C. 1989. A petrified lycopod from the uppermost Devonian of Hook Head, County Wexford, Ireland. *Botanical Gazette* 150: 323-336.

4. Matten, L. C. 1995. The megafossil flora from the Uppermost Devonian of Hook Head, County Wexford, Ireland. Birbal Sahni Centenary Volume, 167-173. Society of Indian Plant Taxonomists, Allahabad, India.

5. Durieux, T., A.-L. Decombeix, C. J. Harper, M. Ramel, C. Mays, and C. Prestianni. 2025. Callixylon seamrogia sp. nov., a new species from the uppermost Famennian (Upper Devonian) of Ireland. Review of Palaeobotany and Palynology 334: 105256.

6. Decombeix, A.-L., C. J. Harper, C. Prestianni, T. Durieux, M. Ramel, and M. Krings. 2023. Fossil evidence of tylosis formation in Late Devonian plants. *Nature Plants* 9: 695-698.

**Acknowledgments:** For their help during fieldwork or/and in the study of the specimens we would like to thank: Marcos AMORES, Catherine GIRARD, Malgorzata HORAJSKA-SHAIKH, Brigitte MEYER-BERTHAUD, and Holly-Anne TURNER.

<footnote n="1">¹ Trinity College Dublin, Dublin, Ireland</footnote>

<footnote n="2">² UMR AMAP, Univ. Montpellier, CNRS, CIRAD, INRA, IRD, Montpellier, France</footnote>

<footnote n="3">³ Natural History Museum Vienna, Vienna, Austria</footnote>

<footnote n="4">⁴ University College Cork, Cork, Ireland</footnote>

<footnote n="5">⁵ Liège University, Liège, Belgium</footnote>

<footnote>* durieupt@tcd.ie</footnote>