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| Zosterophyllum baoyangense Huang & Xue, in Huang, J.-S. Wang, Y.-L. Wang, Liu, Zhao et Xue. 2025. |
Abstract
Plants have evolved different life-history strategies to overcome limited amounts of available resources; however, when and how divergent strategies of sexual reproduction evolved in early land plants are not well understood. As one of the notable and vital components of early terrestrial vegetation, the Zosterophyllopsida and its type genus Zosterophyllum reached maximum species diversity during the Pragian (Early Devonian; ca 410.8–407.6 million years ago). Here we describe a new species, Zosterophyllum baoyangense sp. nov., based on well-preserved specimens from the Pragian-aged Mangshan Group of Duyun, Guizhou Province, China. The new plant is characterized by its small size, K-shaped branching and tiny spikes with 5–10 sporangia. This plant is most likely r-selected, completing its whole lifespan in a short time, and such a strategy contributes to reproduction in a suitable window time. In contrast, most other species of Zosterophyllum and the zosterophyllopsids on a broader scale are larger in body size and have greater investments in fertile tissues, reflected in the size and total number of sporangia. We argue that the zosterophyllopsids probably benefited from the divergence of various life-history strategies and thus constituted a major part of the Early Devonian floras.
Keywords: early land plants, Zosterophyllum baoyangense sp. nov., Early Devonian, life-history strategies
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| Zosterophyllum baoyangense sp. nov. (a,b) PB203562, part and counterpart, showing a fertile axis with K-shaped branching and a terminal spike. Arrows highlight branching points. The parts indicated by arrows c and d are enlarged in (c,d), respectively; (c) K-shaped branching; (d) branching point showing a nearby protuberance (arrow); (e,f) Enlarged view of the terminal spike in (a) and (b); (g) enlarged view of the basal part of the spike in (e). Arrow points to the margin of the basal sporangium. (h) Enlargement of the distal sporangia in (f) (arrow h), showing dehiscence line (white arrow) and peripheral rim along the convex distal margin (the area between two black arrows). Scale bars: (a,b), 10 mm; (c–f), 1 mm; (g,h), 0.5 mm. |
Systematic palaeontology
Class: Zosterophyllopsida Hao & Xue [2013]
Order: Zosterophyllales Hao & Xue [2013]
Family: Zosterophyllaceae Banks [1968]
Genus: Zosterophyllum Penhallow [1892]
Type species Z. myretonianum Penhallow [1892]
Zosterophyllum baoyangense Huang & Xue sp. nov.
Specific diagnoses. Rhizome with K-shaped branching. Erect axis with tiny spikes. Axes 0.5−1.3 mm wide. Spikes, 5.8−10.8 mm high and 2.0−2.8 mm in maximum width, consisting of 5–10 sporangia that are spirally arranged. Sporangia oval to semicircular, 1.6−2.0 mm high and 0.9−1.4 mm wide, departing from axis at an acute angle by a short stalk. Thin peripheral rim ca 80 μm wide, extending along the convex distal margin and lacking thickened dehiscence mechanism.
Etymology. The specific epithet is derived from Baoyang Village, where the fossils were collected.
Holotype designated herein. PB203562
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| Artist’s restoration of part of the Early Devonian Mangshan flora, with plant communities of Zosterophyllum baoyangense sp. nov. at the front, and Teyoua antrorsa, Zosterophyllum australianum and an unnamed zosterophyllopsid to the back. |
Locality and horizon. Baoyang Section, Baoyang Village, Duyun City, Guizhou Province; the lower part of the Mangshan Group; Early Devonian (Pragian; see electronic supplementary material, figure S1).
Repository. All specimens are deposited at the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, China.
Pu Huang, Jia-Shu Wang, Yi-Ling Wang, Lu Liu, Jing-Yu Zhao and Jin-Zhuang Xue. 2025. The smallest Zosterophyllum plant from the Lower Devonian of South China and the divergent life-history strategies in zosterophyllopsids. Proc. R. Soc. B. 292; 20242337. DOI: doi.org/10.1098/rspb.2024.2337
