FIGURE 11 - uploaded by Jason Hilton
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Anatomy and morphology of the megasporangia of Dorsalistachya quadrisegmentorum. (A) Transverse section through a single megasporangium (me), positioned between two microsporangia (mi). The megasporangium displays two wings (w) in the proximal and distal direction and contains the remains of a single megaspore (mg). Slide WP2-0271 E/Top (36). Scale bar = 0.5 mm. (B) Tangential section through a single megasporangium, showing the elongate shape and possible bifurcating wings at the base (w). Slide WP2 0247 (u/18). Scale bar = 0.5 mm. (C) Enlargement of a part of the megasporangium showing the detail of the sporangial wall and wing, diff erentiating inner wall zone (iw) and outer wall zone (ow). Slide WP20265. Scale bar = 100 μ m. (D) Enlargement of a piece of fragmented megasporangium shown in Fig. 11A. Slide WP2-0271 E/Top (36). Scale bar = 50 μ m.
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Premise of the study:
Noeggerathiales are an extinct group of heterosporous shrubs and trees that were widespread and diverse during the Pennsylvanian-Permian Epochs (323-252 Ma) but are of controversial taxonomic affinity. Groups proposed as close relatives include leptosporangiate ferns, sphenopsids, progymnosperms, or the extant eusporangiate f...
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Citations
... The presence of decussate sporophylls in a Carboniferous strobilus highlighted Tetraphyllostrobus as very unusual in the context of the known structural diversity of Paleozoic plants (Friis, 1992). To that end, the genus was initially considered incertae sedis (Gao and Zodrow, 1990) and subsequently it has been treated as a progymnosperm, sphenopsid, sphenophyll, or noeggerathian (Bek and Šimunek, 2005;Wang et al., 2014;Pfefferkorn and Wang, 2016;Wang et al., 2017;Libertín et al., 2014Libertín et al., , 2021. Hexaphyllostrobus kostorhysii and T. broganensis are of similar shape and size (Appendix S2: Table S1). ...
Premise
We studied the 3D morphology of a small, well‐preserved cone from the Pennsylvanian Mazon Creek Lagerstätte to characterize its structure and determine its systematic affinity. Previously tentatively assigned to the enigmatic Tetraphyllostrobus , we show that it differs in key respects from that genus as described.
Methods
We systematically compared the new fossil with relevant Paleozoic cone genera and employed advanced imaging techniques, including scanning electron microscopy, Airyscan confocal super‐resolution microscopy, optical microscopy, and X‐ray microcomputed tomography to visualize and reconstruct the fossil cone in 3D.
Results
The analyses demonstrate unequivocally that the sporophylls of the new Mazon Creek cone are arranged in whorls of six and have characters typical of Sphenophyllales, including epidermal cells with undulatory margins and in situ spores assignable to Columinisporites . The combination of characters, including sporophyll arrangement, anatomy, and spore type, supports the establishment of Hexaphyllostrobus kostorhysii gen. et sp. nov. within Sphenophyllales. Furthermore, we show that Tetraphyllostrobus , although originally described as possessing smooth monolete spores, actually possesses Columinisporites ‐type spores, indicating that it, too, was most likely a sphenophyll.
Conclusions
The recognition of Hexaphyllostrobus contributes to our knowledge of Pennsylvanian sphenophyll diversity, and in particular increases the number of species with in situ Columinisporites ‐type spores. Attribution of Hexaphyllostrobus to Sphenophyllales calls into question current interpretations of Tetraphyllostrobus suggesting that future research on better‐preserved macrofossil material may demonstrate a sphenophyllalean relationship.
... The Xuanwei Formation is a widespread coal-bearing succession in Southwest China that consists of interbedded sandstones, siltstones, mudstones, and coal seams and is assigned to the upper Wuchiapingian to Changhsingian stages of the Lopingian Series (upper Permian: Yao et al., 1980;Bureau of Geology and Mineral Resources of Yunnan Province, 1996;Wang et al., 2011;Wang et al., 2020;Shen et al., 2019;Chen et al., 2022). Plant megafossils from this formation have been investigated extensively Li et al., 1994;He et al., 2008;He et al., 2013;He et al., 2019;He et al., 2020;He et al., 2021;Seyfullah et al., 2009;Wang et al., 2014;Wang et al., 2017;Feng et al., 2017;Feng et al., 2023;Guo et al., 2020;Guo et al., 2021;Zhou et al., 2021Guo et al., 2024). The fossil assemblages reflect a typical Lopingian Gigantopteris Flora Feng et al., 2023) of the Cathaysian Realm (sensu Meyen, 1987). ...
... The Xuanwei Formation is correlated with the upper Wuchiapingian to the Changhsingian Stage of the Lopingian Series, Permian (Wang et al. 2011;Shen et al. 2019;Wang et al. 2020). Diverse plant megafossils have been reported from the Xuanwei Formation in the Khangdian Oldland at the western margin of the South China Block (Yunnan, Guizhou, and Sichuan provinces), including lycophytes, sphenophytes, ferns, seed ferns, conifers, cycadophytes, and ginkgophytes (Gu & Zhi 1974;Zhao et al. 1980;Li et al. 1994;Hilton et al. 2004;Seyfullah et al. 2009;D'Rozario et al. 2011;He et al. 2013;Wang et al. 2014;Feng et al. 2017;Wang et al. 2017;Feng et al. 2020;Guo et al. 2021;Feng et al. 2023). This plant assemblage represents a typical Henanotheca qingyunensis sp. ...
... and is correlated with the upper Wuchiapingian to Changhsingian Stage of the Lopingian Series, Permian Bureau of Geology and Mineral Resources of Yunnan Province, 1996;Wang et al., 2011;Wang et al., 2020;Shen et al., 2019;Yan et al., 2019). Diverse fossil plants from the Xuanwei Formation have been documented in the study area, including lycophytes, sphenophytes, ferns, pteridosperms, conifers, cycadophytes, and ginkgophytes (Gu and Zhi, 1974;Zhao et al., 1980;Li et al., 1994;Hilton et al., 2004;He et al., 2013;Seyfullah et al., 2009;D'Rozario et al., 2011;Wang et al., 2014;Wang et al., 2017;Feng et al., 2017;Feng et al., 2020;Feng et al., 2023;Guo et al., 2020;Guo et al., 2021;Zhou et al., 2021). ...
A new species of adpressed leptosporangiate fern, Szea yunnanensis sp. nov., is described from the Xuanwei Formation (upper Permian) of Yunnan Province, Southwest China. Fronds of this new species are at least bipinnate, with suboppositely to alternately arranged cladophleboid pinnules. Fertile pinnules are triangular to falcate shaped and show slightly decurrent entire bases, acute apices, and proximally lobed margins. Sporangia are grouped into abaxial sori arranged in one row on each side of the midvein from the basal to the 1/2–2/3 portion of the pinnule. The number of sori per row varies from one to four. Sori are exindusiate, ovoid/ellipsoid, with a diameter of 1.3 mm on average, and each consists of approximately 25 sporangia. Sporangia with biseriate annuli are ovoid or ellipsoid, approximately 330 μm long and 230 μm wide, and each produces approximately 100 or more spores. Sporangial walls have one layer of polygonal/elongated cells. Trilete auriculate in situ spores of the Triquitrites-type have verrucate-rugulate-reticulate sculpture. The exine is 2–3 μm thick and without identifiable layers. The family relationship of Szea may belong to the Gleicheniaceae or the Sermayaceae, but the combination of sporangium and spore characteristics of Szea inclines us to place this genus among the family Incertae Sedis. The family relationships of Chansitheca, Henanotheca, and Oligocarpia which were originally affiliated with the Gleicheniaceae are also questionable.
... The Xuanwei Formation unconformably overlies the Emeishan Basalt and is overlain conformably by the Kayitou Formation (Feng et al., 2020b). Plant megafossils of this formation have been investigated extensively Li et al., 1994;Hilton et al., 2004;He et al., 2008;He et al., 2010;He et al., 2013;He et al., 2020;He et al., 2021;Seyfullah et al., 2009;Wang et al., 2014;Wang et al., 2017;Feng et al., 2017;Yang et al., 2019;Guo et al., 2020;Feng et al., 2020a;Guo et al., 2021;Zhou et al., 2021;Feng et al., 2023) and indicate a typical Lopingian flora (Feng et al., 2020a) of the Cathaysian Realm (Meyen, 1987). ...
... Apart from thick conglomerates in the basal part, the majority of the Xuanwei Formation consists of interbedded sandstone, siltstone, mudstone, and coal seams Bureau of Geology and Mineral Resources of Yunnan Province, 1996;Wang et al., 2011;Wang et al., 2018). Plant macrofossils are abundant in the Xuanwei Formation and have been investigated extensively in this region Li et al., 1994;He et al., 2008;He et al., 2010;He et al., 2013;He et al., 2020;He et al., 2021;Seyfullah et al., 2009;Wang et al., 2014;Wang et al., 2017;Feng et al., 2017;Yang et al., 2019;Guo et al., 2020;Guo et al., 2021;Zhou et al., 2021). The assemblages characterize a typical Feng et al., 2020a). ...
Lycophytes were an important group of plants in the late Permian (Lopingian) vegetation of Southwest China. However, our understanding of these lycophytes is based mostly on the study of megafossil specimens. Here, we describe a unique lycophyte megaspore, Paxillitriletes permicus Sui, McLoughlin et Feng sp. nov., from the Lopingian Xuanwei Formation of Yunnan Province, Southwest China. This trilete megaspore is characterized by prominent membraneous triradiate flanges, long bifurcate spines, an arcuate ridge expanded into a zona, and triangular to polygonal reticulate sculpture. Ultrastructural analysis reveals that the megaspore wall consists of four layers. The innermost layer is the foot layer, which forms a thin and solid basal lamina. It is covered by a dense layer containing small and parallel sporopollenin grains. A thick spongy layer is developed exterior to the dense layer and consists of elongate, curved, and intersected sporopollenin units with porous zones. The outermost layer is dense, of variable thickness, and forms the processes. Morphological and ultrastructural features indicate that the new megaspore belongs to a herbaceous isoetalean. This is the first detailed investigation of megaspores from the Lopingian of China using scanning and transmission electron microscopy. Our discovery represents the oldest occurrence of Paxillitriletes, and adds to the diversity of late Permian lycophytes in the Cathaysian Flora in the paleotropics of the eastern Tethys Ocean.
... The Xuanwei Formation is correlated with the upper Wuchiapingian to the Changhsingian Stage of the Lopingian Series, Permian Shen et al., 2019). Fossil plants from the Xuanwei Formation have been extensively investigated in the study area (Gu and Zhi, 1974;Zhao et al., 1980;Li et al., 1994;Hilton et al., 2004;He et al., 2008He et al., , 2010He et al., , 2013Seyfullah et al., 2009;D'Rozario et al., 2011;Wang et al., 2014Wang et al., , 2017Feng et al., 2017;. The plant assemblage in the Xuanwei Formation encompasses lycophytes, sphenophytes, ferns, pteridosperms, cycadophytes, and ginkgophytes, representing a typical Gigantopteris flora of the Cathaysian region that formed rainforest ecosystems in the tropics of the eastern Paleo-Tethys Ocean . ...
A new species of adpressed marattialean fern with vegetative and fertile pinnules, Pectinangium xuanweiense sp. nov., is described from the Lopingian (upper Permian) in eastern Yunnan and western Guizhou provinces, Southwest China. The fronds of this new species are at least bipinnate, with linear to lanceolate ultimate pinnae. The pinnules are alternately arranged and pecopterid-type with pinnate venation. Fertile pinnules show recurved margins and abaxially bear a row of synangia on each side of the midvein. Synangia are 0.7 mm long and 0.4 mm wide on average, arranged in a density of approximately 16 per centimeter. Each synangium consists of four sporangia that are completely fused in well-regulated rectangular/ovoid shapes in the distal view. Sporangia are exannulate, 370 μm long and 200 μm wide on average. The sporangial walls are composed of at least three layers of elongated rectangular to polygonal cells. In situ spores are circular to oval, 25–(30)–35 μm in diameter, with trilete marks and microverrucate sculptures. Ultrastructural investigations indicated that the exine encompasses a perine, sexine, and nexine. In situ spores correspond to Verrucosisporites if found as sporae dispersae, and thus indicate that P. xuanweiense sp. nov. belongs to the Acitheca miltonii Group (palynological grouping) of Paleozoic marattialeans. Our study provides insight into the diversity of late Permian marattialeans in the tropics of the eastern Paleo-Tethys ocean.
... This is different from the previously recognized tuff samples from the Sanjiaoshu Mine (Hilton et al., 2004) that contained permineralized fossils plants broken up and size sorted by taphonomic processes and they were probably deposited as pyroclastic flows or re-worked as epiclastic deposits such as lahars. The volcanic tuff from nearby Huopu coal mine (Neregato et al., 2016;Wang et al., 2017) in the Xuanwei Formation also contains highly fragmented and size sorted fossil plants; it may also have been deposited as pyroclastic flows or lahars (Neregato et al., 2016). ...
A new species of the Marattialean fern frond Rothwellopteris is proposed for specimens preserving both morphology and anatomy from the Wuchiapingian–Changshingian (late Permian) aged Xuanwei Formation of South China. Fronds are at least bipinnate and bear falcate, pecopteroid pinnules with a thin lamina. The penultimate pinna rachis has a polycyclic vascular system with endarch primary xylem and longer vascular bundles located abaxially in a single radial row, and shorter vascular bundles adaxially arranged in two radial rows, with a vascular bundle sheath of sclerenchyma cells. Ground tissue comprises parenchyma cells and numerous secretory ducts. Features of the new species suggest that it was adapted for mesomorphy, while the previously recognized species Rothwellopteris pecopteroides was adapted for xeromorphy or was a sun-leaf. Like R. pecopteroides, the new species displays a mosaic of morphological and anatomical features characteristic of both the Paleozoic family Psaroniaceae and the extant family Marattiaceae; we interpret it to be a member of the evolutionary stem-group from which stratigraphically younger Marattiaceae evolved. Our findings show that the stem- to crown-group transition within Marattiales commenced before the end of the Permian and that a greater diversity of transitional forms can now be recognized from the late Permian and include the genera Compsopteris, Rothwellopteris, Tietea and Tuvichapteris.
... Diverse plant megafossils, including lycophytes, sphenophytes, ferns, seed ferns, gigantopterids, conifers, cycadophytes, and probable ginkgophytes, have been reported from the Xuanwei Formation in the Khangdian Oldland at the western margin of the South China Block (belonging to the present-day Yunnan, Guizhou, and Sichuan provinces, Southwest China) (Gu and Zhi, 1974;Zhao et al., 1980;Li et al., 1994;Hilton et al., 2004;He et al., 2008He et al., , 2010He et al., , 2013Seyfullah et al., 2009;D'Rozario et al., 2011;Wang et al., 2014Wang et al., , 2017Feng et al., 2017;. The plant assemblage of the Xuanwei Formation represents a typical Gigantopteris flora of the Cathaysian floristic region forming rainforest ecosystems in the tropics of the eastern Paleo-Tethys Ocean . ...
The Lopingian (upper Permian) in Southwest China yields diverse marattialean plants; however, most of these have been recorded as isolated fragments of fronds, pinnules, and stems. Marattialean Qasimia specimens were recently collected from the upper Permian Xuanwei Formation of Yunnan Province, Southwest China. The well-preserved synangia, sporangia, and prominent in situ spores permitted the emendation of the genus Qasimia and the establishment of the species Q. yunnanica sp. nov. This plant possesses alternately or sub-oppositely arranged fertile pinnules with abaxially attached synangia. The synangia are sessile and bivalvate, with a length nearly half the width of the pinnules. A synangium valve consists of approximately 20 long ellipsoids and laterally fused sporangia. In situ spores of the Punctatosporites type are monolete, 97 × 74 μm on average, with a microverrucate/microgranulate to vermiculate sculpture; these represent the largest in situ spores of this type. The sporangial wall has at least two layers of polygonal/elongated cells. The exine comprises a perine, sexine, and nexine. The characteristics of the marattialeans with bilaterally symmetrical synangia were analyzed based on a comparison of eight related genera in the late Paleozoic and Marattia after the late Paleozoic. The Qasimia-type synangium represents the earliest occurrence of bivalvate synangium, which is a typical feature of modern marattialeans. Although the origin of the bilaterally symmetrical marattialean synangia remains elusive, marattialeans with this type of synangia first appeared in the Euramerica during the late Carboniferous and then migrated to the Cathaysia, where they became more prosperous until the late Permian.
... In contrast, Noeggerathiales (9) have at times been proposed as progymnosperms (9)(10)(11)(12), but this has been controversial. Comprising ∼20 genera and 50 species, Noeggerathiales are known from the late Carboniferous-Permian (323 to 251 Ma) tropical floras in North America, Europe, and East Asia (10), ...
... where they are identified as a related group based on shared features of heterospory, adaxial sporangial attachment to "sporophylls," longitudinal sporangial dehiscence, plagiotropic pinnule attachment to the rachis, and once-pinnate compound megaphylls (9)(10)(11)(12). However, their systematic position remained uncertain because details of their stem anatomy were unknown. ...
... In the absence of this anatomical information, they have been postulated as close relatives of the progymnosperms, leptosporangiate ferns, sphenopsids, the extant fern Tmesipteris, or as a distinct class of their own (see ref. 9 for summary). Recently, leaves of Plagiozamites oblongifolius that were interpreted as noeggerathialean (9) have also been interpreted as cycads (13). Wang et al. (9) considered the Noeggerathiales to be putative progymnosperms, but as their specimens lacked wood, a more confident assignment was not possible. ...
Significance
There were two heterosporous lignophyte lineages of which only one, the seed plants, survived the Permian–Triassic mass extinction. Based on exceptionally complete fossil trees from a 300-My-old volcanic ash, the enigmatic Noeggerathiales are now recognized as belonging to the other lineage. They diversified alongside the primary seed plant radiation and constitute seed plants’ closest relatives. Noeggerathiales are reconstructed as members of a plexus of free-sporing woody plants called progymnosperms, extending their age range by 60 My. Following the origin of seed plants, progymnosperms were previously thought to have become gradually less abundant before dying out in Carboniferous. We show they diversified and evolved complex morphologies including cone-like structures from modified leaves before going extinct at the Permian–Triassic extinction.
