Imagine ovules not hanging from branches, but crowded by the hundreds on the undersides of leaves. That was precisely the reproductive strategy of Ganiopteris , a newly discovered seed plant from Jiangxi Province, China, that lived about 360 million years ago.
The discovery, led by Professor De-Ming Wang of Peking University and published in National Science Review , reveals the earliest-known seed plant with ovules attached directly to leaves. Before this find, the earliest evidence of leaf-borne ovules came from the late Carboniferous—a gap of at least 40 million years.
Ganiopteris was collected from the lower Carboniferous Huashanling Formation at three localities in northern Jiangxi Province. The ovuliferous fructifications (ovule-bearing organs) or megasporophylls are in a loose helical arrangement. Each megasporophyll, up to 11.8 cm long, is scutum-shaped.
What makes Ganiopteris truly remarkable is the underside of each leaf: it is densely covered with hundreds of tiny ovules, each about 2.6 mm long and 1.4 mm wide. The upper surface displays a distinctive radial pattern of veins, while wing-like lobes line the leaf margins.
A major evolutionary shift
Seed plants from the Late Devonian and early Carboniferous bore ovules at the terminal tips of leafless axes. These early ovules likely relied on their own photosynthetic capacity or on the photosynthetic activity of protective cupules for nutrient supply. By contrast, Ganiopteris could photosynthesize through its broad leaves to support its numerous small ovules. The transition from axial- to leaf-borne ovules marks a major evolutionary milestone. The authors interpret this shift within the framework of the telome theory, which describes how three-dimensional branching systems became flattened and fused into laminate leaves over evolutionary time. Ganiopteris provides a tangible fossil example of this process in seed plants.
"This discovery fundamentally changes our understanding of when and how seed plants evolved the strategy of attaching ovules to leaves," said Professor Wang. "For the first time, we have clear evidence that this key reproductive innovation occurred at the very beginning of the Carboniferous period, much earlier than previously thought."
A window into the origin of glossopterids
Glossopterids were the dominant seed plants of Gondwana during the Permian and their fossil remains serve as iconic paleobotanical evidence supporting Wegener's continental drift theory. Despite the widespread occurrence of glossopterid palynomorphs in Carboniferous strata, no macrofossils of the group had ever been found before the Permian. The present study sheds new light on their elusive origins.
Ganiopteris lived in South China Block, which at the time of early Carboniferous was located in the Southern Hemisphere, close to the eastern margin of Gondwana and within the tropics. Its reproductive leaves look remarkably similar to those of Permian glossopterids, suggesting that it could represent an early precursor. If this interpretation holds, the origin of Permian glossopterids can thus be traced back to the early Carboniferous.
Nevertheless, a clear morphological distinction separates the two groups. In glossopterids, each reproductive leaf is subtended and protected by a vegetative leaf from below. Ganiopteris lacks such a protective structure entirely.
Why no protective leaf?
The answer may lie in the biological and paleogeographical conditions of South China Block during the early Carboniferous. This period fell within two major evolutionary gaps—the "Hexapoda gap" and "Romer's gap"—when herbivorous insects and terrestrial vertebrates were exceptionally rare. Meanwhile, South China Block occupied low-latitude tropics and likely enjoyed abundant rainfall. With little threat from herbivores and low risk of water loss via desiccation, the ovules on the undersides of Ganiopteris leaves simply had no need for an extra protective leaf.
Professor De-Ming Wang of Peking University led the study as the first and corresponding author. The co-authors included Associate Researcher Yi Zhou (Sun Yat-sen University), Dr. Jiang-Nan Yang (Zhejiang Institute of Geosciences), Associate Professor Le Liu (China University of Mining and Technology (Beijing)), Associate Professor Min Qin (Linyi University), and PhD students Peng Xu and Yue-Han Pan (Peking University).
This study was supported by the National Natural Science Foundation of China (42130201, 42472009) and the National Key Research and Development Program of China (2022YFF0800200).
National Science Review