Fruits in the Permian? Baipingfructus Provides Early Evidence for the Origin of Angiosperms

Flowers and fruits are among the most characteristic reproductive structures of angiosperms. Exactly when angiosperms first appeared has long remained uncertain, but a group of plant fossils from Henan Province, China, may push their history back into the Permian. A newly described fossil fruit, named Baipingfructus wuii, is currently known only from its fruit structure. No leaves, branches, or other plant organs have yet been found in definite organic connection with it, so the name refers to a fossil taxon established on the basis of the fruit itself.

The fossils come from the Xiaofengkou Formation near Baiping Town, Dengfeng City, Henan Province. The researchers examined two flattened specimens preserved in siltstone. Both are roughly oval in shape, measuring about 8–11 mm long and 5–8 mm wide. In addition to conventional photography and stereomicroscopy, the team used scanning electron microscopy to examine structures at the cellular scale.

Fossil locality and stratigraphic information of Baipingfructus wuii. (a) Fossil locality in the suburbs of Dengfeng City, Henan Province, China; (b) location of the fossil locality in China, indicated by a red dot; (c) outcrop of the fossil-bearing strata; (d) position of the fossil-bearing horizon in the stratigraphic column（Image source：Huang W et al. (2025)， CC BY 4.0 ）

Within the cavity of one specimen, seven rounded structures measuring about 1–1.3 mm in diameter can be distinguished. They differ in both preservation and developmental stage and were interpreted as in situ ovules or seeds. The wall surrounding them is approximately 0.6–1 mm thick and can be divided into three layers: the exocarp, mesocarp, and endocarp. The mesocarp contains interconnected sclerenchymatic tissue forming a branched, network-like framework, whereas the endocarp consists of elongated cells.

Scanning electron microscopy images of the pericarp of Baipingfructus wuii. (a) Three-layered structure of the pericarp and the three-dimensional sclerenchymatic framework in the mesocarp; (b) details of the exocarp (1) and mesocarp (2); (c) neatly arranged macrosclereids in the mesocarp; (d) exocarp, mesocarp, and endocarp (3), with the endocarp composed of elongated cells（Image source：Huang W et al. (2025)， CC BY 4.0 ）

The two fossils were interpreted as fruits because a single enclosing structure contains multiple millimeter-sized reproductive bodies. If the entire fossil represented only a seed, ovule, or sporangium, it would be difficult to explain the presence of several separate structures inside it. On this basis, the authors considered a fruit enclosing multiple ovules or seeds to be the interpretation most consistent with the observed anatomy.

Holotype (PB209247) and paratype (PB209248) specimens of Baipingfructus wuii. (a–b) Holotype fruit containing seven in situ seeds or ovules at different developmental stages; (c) sclerenchymatic framework in the pericarp of the paratype; (d) enlarged view of one relatively mature seed in the holotype（Image source：Huang W et al. (2025)， CC BY 4.0 ）

One of the more developed internal structures also preserves a relatively complete seed coat. Four layers were recognized, from the outside inward: the cuticle layer, palisade layer, hypodermal layer, and endotesta. The palisade layer contains closely packed, elongated macrosclereids, whereas the hypodermal layer contains conspicuous large intercellular spaces and vertical wall-like structures formed by sclerenchymatic cells. Several other reproductive bodies within the same fruit have much less developed seed coats, suggesting that they did not mature synchronously. Some may still have been at the ovule stage or at a very early stage of seed development.

Scanning electron microscopy images of the holotype of Baipingfructus wuii. (a) Entire fruit showing the closed apex, seven in situ seeds or ovules at different developmental stages, and a partially preserved pericarp; (b) closed apex of the fruit; (c–d) a less mature and a more mature seed, respectively; (e–f) details of the seed coat of the more mature seed, showing intercellular spaces and the cuticle layer, palisade layer, hypodermal layer, and endotesta; (g) poorly developed sclerenchymatic framework in the mesocarp（Image source：Huang W et al. (2025)， CC BY 4.0 ）

Can Baipingfructus wuii therefore be regarded as an angiosperm? One of the defining features of angiosperms is that their ovules are enclosed before pollination, with the resulting seeds remaining within an enclosed structure as they mature. The tip of B. wuii appears closed, while its interior contains both apparently immature ovules and more developed seeds. The authors therefore proposed that its ovules were probably already enclosed before pollination.

The fossils, however, do not directly preserve the pollination process, and there is currently no direct evidence showing how pollen entered the reproductive organ. The interpretation that the ovules were enclosed before pollination is therefore inferred from the closed condition of the organ and the developmental states of the seeds and ovules. This leaves an important uncertainty when assessing whether the fossil satisfies the stricter definition of an angiosperm. The fossils clearly show that the reproductive bodies were enclosed, but the precise point during the pollination process at which enclosure occurred is supported only indirectly.

The hypodermal layer of the seed coat in B. wuii also contains unusually large intercellular spaces. The researchers proposed that these spaces may have increased buoyancy in water, raising the possibility that the seeds were dispersed by water. The well-developed three-dimensional sclerenchymatic framework in the pericarp was also interpreted as potentially providing cushioning and resistance to mechanical impact. On this basis, the authors further suggested that the fruits may have been borne on plants of some height.

Scanning electron microscopy images of the paratype of Baipingfructus wuii. (a) Fruit apex and sclerenchymatic framework in the pericarp; (b–c) branched sclerenchymatic framework and neatly arranged macrosclereids in the mesocarp; (d–f) crystalline structures with spiny margins in the pericarp; (g) neatly arranged macrosclereids in the pericarp（Image source：Huang W et al. (2025)， CC BY 4.0 ）

The Xiaofengkou Formation is assigned to the Permian, and the fossils of B. wuii were estimated to be more than 245 million years old. The researchers also compared the new taxon with previously proposed Permian angiosperm candidates. Because these fossils differ substantially in size, structure, and number of ovules, the authors argued that angiosperms may already have been relatively diverse during the Permian.

The presence of multiple ovules or seeds at different developmental stages enclosed within a single reproductive structure gives B. wuii several features strongly suggestive of angiosperm affinity. For this fossil to become important evidence for a Permian origin of angiosperms, however, further work will need to determine whether alternative interpretations involving other ancient seed plants can be excluded, and whether the apparently immature ovules were indeed already enclosed before pollination.

Author: Shui-Ye You

Reference:

Huang W et al. (2025). Perfect Permian Fruits. Research Square.