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Co-occurring gymnosperm foliage in the Late Triassic plant fossil assemblage from Mt. Falla, Queen Alexandra Range, East Antarctica. A, Heidiphyllum elongatum (Morris) Retallack. T5-58. B, Mat of partially overlapping leaves of Heidiphyllum elongatum (Morris) Retallack and Dejerseya lobata (Jones et de Jersey) Herbst emend. nov. T5-58. C, Dicroidium lancifolium (Morris) Gothan; parts of several individual fronds. T5-38.
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A new Triassic seed fern is described on the basis of a large collection of well-preserved plant compressions from the Upper Triassic of Mt. Falla, Queen Alexandra Range, central Transantarctic Mountains. The foliage is simple entire-margined to pinnatifid to partly pinnate and is assigned to Dejerseya lobata (Jones et de Jersey) Herbst emend. nov....
Citations
... However, when taken collectively, stomatal morphology, leaf morphology, and vein architecture do suggest a relationship of Furcula with Peltaspermales. This group of seed plants ranged primarily from the late Carboniferous to the end of the Triassic (Thomas, 1932;Townrow, 1960;Kerp, 1988;Bomfleur et al., 2011;Vajda et al., 2023), although rare relictual populations may have persisted in southern high latitudes into the Jurassic (McLoughlin et al., 2015;Bomfleur et al., 2018;Elgorriaga et al., 2019). Traditionally included in the polyphyletic 'seed ferns', past phylogenetic studies incorporating fossil groups have resolved Peltaspermales in diverse relationships with other seed plant groups (McLoughlin, 2021). ...
... These taxa also shared a similar latitudinal range during the Late Triassic, occupying the midlatitudes of northern Pangaea. It has to be noted that Vittaephyllum, although generally attributed to Peltaspermales (Bomfleur et al., 2011), has not yet been associated with peltaspermalean reproductive structures. Future discovery of such an association would be pivotal to test the hypothesis of relationship between Vittaephyllum and Furcula and the other peltaspermalean genera. ...
Leaf venation is a pivotal trait in the success of vascular plants. Whereas gymnosperms have single or sparsely branched parallel veins, angiosperms developed a hierarchical structure of veins that form a complex reticulum. Its physiological consequences are considered to have enabled angiosperms to dominate terrestrial ecosystems in the Late Cretaceous and Cenozoic.
Although a hierarchical‐reticulate venation also occurs in some groups of extinct seed plants, it is unclear whether these are stem relatives of angiosperms or have evolved these traits in parallel. Here, we re‐examine the morphology of the enigmatic foliage taxon Furcula, a potential early Mesozoic angiosperm relative, and argue that its hierarchical vein network represents convergent evolution (in the Late Triassic) with flowering plants (which developed in the Early Cretaceous) based on details of vein architecture and the absence of angiosperm‐like stomata and guard cells.
We suggest that its nearest relatives are Peltaspermales similar to Scytophyllum and Vittaephyllum, the latter being a genus that originated during the Late Triassic (Carnian) and shares a hierarchical vein system with Furcula.
We further suggest that the evolution of hierarchical venation systems in the early Permian, the Late Triassic, and the Early Cretaceous represent ‘natural experiments’ that might help resolve the selective pressures enabling this trait to evolve.
... All specimens are stored in the Research Center of Paleontology and Stratigraphy, Jilin University, Jilin Province, and all prepared slides and SEM stubs are housed in the College of Paleontology, Shenyang Normal University, Liaoning Province, China. And the literature we used to describe the leaf anatomy of Coniopteris mainly followed Harris (1961) and Bomfleur et al. (2011). (Harris, 1961). ...
... Townrovia is known based on material from the Triassic of the Southern Hemisphere (Retallack, 1981;Bomfleur et al., 2011). It is an irregularly flattened pollen organ consisting of a main axis bearing unforked or forked lateral branches that terminate in an enlarged head (receptacle) that bears pollen sacs in two or more rows. ...
... In T. petasata Retallack from the Middle Triassic of New Zealand, the terminal head is described as flanked by laminar wings (Retallack, 1981), somewhat similar to the valves of Harrisiothecium. However, the laminar wings are not recorded in better preserved material of Townrovia polaris Bomfleur, Ed.L.Taylor, T.N.Taylor, Serbet, M.Krings et Kerp from the Upper Triassic of Antarctica (Bomfleur et al., 2011). ...
... Although Harris (1964) transferred the Yorkshire Jurassic Pachydermophyllum leaves to Pachypteris on the basis of insufficient and inconsistent differentiation of key characters, many subsequent authors have continued to recognize Pachydermophyllum, predominantly in Southern Hemisphere Mesozoic assemblages, based on its more elongate leaflets and strongly verrucate rachis (Retallack, 1977(Retallack, , 1981McLoughlin et al., 2002). There remain uncertainties about the differentiation of Kurtziana and Pachydermophyllum, since their diagnoses are similar, except that the latter incorporates cuticular features not available in the former (Anderson and Anderson, 2003;Bomfleur et al., 2011). Elgorriaga et al. (2019) noted that the cuticular features of several Pachydermophyllum species are strikingly similar to those of Lepidopteris, indicating a possible peltaspermalean affinity. ...
... Bomfleur & Kerp (2010) included leaves with similar-sized but essentially entire-margined pinnules in D. dubium. However, based on macromorphological and micromorphological features, including the lack of subsidiary-cell papillae, these ought to remain assigned to a separate species, D. lancifolium (see also Boucher et al. 1993;Bomfleur et al. 2011b Fig. 8). Pinnules comparatively large, on average broader than 5 mm and stout (shorter than wide) to about equidimensional, of variable shape; some specimens with short, more or less rounded rectangular to rhombic pinnules (Pl. ...
... Sporangia of P. helbyi contain pollen of Falcisporitestype (Retallack, 2002). In these features, P. helbyi resembles pollen organs of peltasperms of a genus Townrovia (Retallack, 1981;Bomfleur et al., 2011) or pollen organs of corystosperms of the genus Pteruchus Thomas, 1933(Thomas, 1933Yao et al., 1995), which occur in the Triassic of Gondwana. Probably, P. helbyi should be affiliated to one of these genera, however, this decision might be made after a study of the typematerial only. ...
... This group is largely represented by medium to large-sized bisaccate pollen belonging to the pollen grain genera Alisporites/Falcisporites, Pteruchipollenites, Sulcosaccispora and Platysaccus. These forms are comparable with in situ pollen grains obtained from Pteruchus microsporophylls attributed to Umkomasiales (Van Konijnenburg- Van Cittert, 1971;Taylor et al., 1984;Osborn and Taylor, 1993;Yao et al., 1995;Traverse, 2007), but were also recovered from fertile organs attributed to conifers (Balme, 1995;Traverse, 2007), Peltaspermales (Van Konijnenburg-Van Cittert, 1971;Bomfleur et al., 2011a), and gymnosperms of uncertain affinity (Clement-Westerhof, 1974). However, Hamad et al. (2008) noticed that floras locally dominated by elements of Umkomasiales (Dicroidium) correlates with high abundances of Alisporites/Falcisporites. Thus, considering that Alisporites/Falcisporites is the most abundant pollen form recorded, and Umkomasiales were the dominant seed plant in Gondwana and central-western Argentina during the Triassic, including the Cerro de Las Cabras Formation (Brea et al., 2009;Cariglino et al., 2016), it can be assumed that these pollen grains were mostly produced by Umkomasiales. ...
... Middle-Late Triassic Peltasperms are interpreted as opportunistic, early successional plants that were particularly successful in colonizing stressed wetland environments, and that would have preferred mesothermal and hygrophytic conditions (Bomfleur et al., 2011a). Therefore, they are also regarded as RS-strategist shrubs. ...
The Cerro de Las Cabras Formation provides a great opportunity for advancing the understanding of Middle Triassic paleoclimates and terrestrial ecosystems. Previous palynological studies conducted at the type locality suggest it developed in a humid and warm environment, however, other lines of evidence would indicate rather semiarid conditions during its deposition. In order to test the first hypothesis, these same palynofloras are re-studied with a new methodological approach. The presented Eco-Guild model provides a conceptual framework for identifying the main abiotic factors that rule vegetation dynamics and composition. It incorporates the moisture requirement, temperature preference, adaptive strategy and body size of parent plants into the context of ecological successions.for their statistical analysis. The paleoecological re-study of palynofloras led to the identification of four palynophases (Woodland “A”,“B″, Riparian Forest “A”,“B″, Palustrine, Lacustrine “A”,“B″) related to two distinct plant zonations: a riverine zonation characterized by ruderal plants living in ephemeral to intermittent fluvial streams, and a lacustrine zonation which is subdivided into a stress-tolerant plant community related to standing water bodies of alkaline-saline conditions, and a plant association linked to small freshwater bodies in the surrounding floodplain area. Around these wetland areas were mesophytic forests of gymnosperms. On an individual scale, this whole ecosystem developed in a highly stressed environment but without major disturbance episodes. However, in stratigraphic terms, it developed under highly fluctuating climatic circumstances. Furthermore, at the middle part of the studied section a significant pulse of moistness was detected, which would be coincident to a major humidity episode occurred during the late Anisian–early Ladinian in central-western Argentina. These results would confirm for the first time the presence of this climatic event in the Uspallata Group (Cacheuta Sub-basin), thereby improving the knowledge regarding the paleoclimatic evolution of southwestern Gondwana during the Middle Triassic.
... In the Late Pennsylvanian and early Permian, peltasperms first appear in strata deposited under seasonally-dry conditions, including channel fills, flood basins, and shallow marine settings (Remy, 1975;Boyarina, 1994Boyarina, , 2010Kerp et al., 2001;DiMichele et al., 2013b;Falcon-Lang et al., 2015). Based on their absence from nearly all Pennsylvanian wetland floras, callipterid peltasperms may have evolved in seasonally dry habitats in areas less likely to be fossilized, and diversified as the aridity increased in the Permian (DiMichele et al., 2005a;Booi et al., 2009;Bomfleur et al., 2011;Wan et al., 2016). Callipterid peltasperm leaves in general are coriaceous, and some possible adaptations to mesic or xeric conditions have been noted for certain species. ...
During the Late Pennsylvanian, seasonality and rainfall increased in western Pangea, which led to the expansion of "mixed" floras composed of a combination of wetland and drought-tolerant plants. One notable example is the flora of the Kinney Brick Quarry, a Missourian Lagerstätte southeast of Albuquerque, New Mexico, USA, deposited in an embayment by a prograding delta in a seasonal, subhumid climate. A controlled excavation of the quarry and bed-by-bed quantitative analyses of the floral composition revealed a transition from dominance by wetland plants to drought-tolerant plants. In this study, we provide a visual reference of important plant taxa from each of the six productive beds in the controlled excavation. Pteridosperms, conifers, and filicalean ferns are present in all six beds; lycopsids, marattialean ferns, and cordaitaleans range through Beds 2-5; sphenopsids, dicranophylls, and noeggerathialeans span Beds 2-6; and Taeniopteris species are present only in Bed 4. The stratigraphic ranges of plants at Kinney suggest that, although there were changes in species dominance patterns, the overall species pool stayed consistent throughout deposition of the strata. We also hypothesize the habitat preferences of fossil plant taxa from Kinney based on morphological adaptations, modeled physiological requirements, and depositional environment interpretations of other localities where the same plant species occur. These interpretations suggest a landscape with varied microhabitats accommodating plants with an array of moisture tolerance levels, with wetland plants colonizing the shoreline, along rivers, and other moist substrates, and meso-and xeromorphic plants occupying areas experiencing seasonal drought.
... Plant taxa recorded in the Potrerillos-Cacheuta sequence and the Los Rastros Formation (except for Equisetales and ferns) are considered to have been deciduous (Pigg 1990;Axsmith et al. 1998;Cúneo et al. 2003;Bomfleur & Kerp 2010;Bomfleur et al. 2011Bomfleur et al. , 2013Escapa et al. 2011;Mays & Mcloughlin 2019) and the features observed in most of the taphonomic modes suggest that abscission was by physiologic or natural processes. The taphonomic attributes are compatible with transport by water flow, except for the TM-2, in which materials were transported by aerial dispersion (wind). ...
The impact of volcanic activity and trophic state on the preservation of plant remains from two Triassic palaeolake deposits in western Gondwana is investigated. Six taphonomic modes are identified for the Potrerillos–Cacheuta sequence and the Los Rastros Formation, along with proposed taphonomic pathways for each mode. The taphonomic pathways were compared with those proposed for the Agua de la Zorra Formation, a coeval lacustrine‐deltaic succession. In all three cases, plant preservation in off‐shore lacustrine facies was enhanced by anoxic bottom conditions. In the more proximal near‐shore facies, a high sedimentation rate would have been factor that enhanced the preservation. Variation in relative abundance and taxonomic diversity between the three successions are attributed to ecological differences rather than taphonomic differences among the lake systems. No evidence was recorded that the preserved plant material was produced by volcanic trauma. The preservation of the cuticle recorded in the Cacheuta Formation was likely enhanced by the apparently low thermal maturation of the rock and the presence of tuffaceous horizons. In the three successions, the abundance and distribution of remains throughout the sections suggest that the trophic state of the lake did not influence the preservation of the plant.
... The Helliwell Formation is correlated with members A to C of the Lashly Formation in southern Victoria Land and with the middle and upper part of the Fremouw Formation, central Transantarctic Mountains, based on (1) high proportion of carbonaceous overbank deposits, (2) homogeneous fine to medium grain size and prominent volcaniclastic component of sandstone intercalations, (3) common occurrence of Middle to Late Triassic plant compression fossils, including Heidiphyllum, Dicroidium, Linguifolium and Dejerseya, and (4) abundant occurrences of silicified peat and wood, including Kykloxylon (see Barrett 1969;Korsch 1974;Barrett et al. 1986;Collinson et al. 1987Collinson et al. , 1994Bomfleur et al. 2011;Escapa et al. 2011;Decombeix et al. 2014;Oh et al. 2016). Likewise similar in lithology and sedimentological features is unit 3 of the upper Parmeener Supergroup in Tasmania (Forsyth 1987), including the upper Cluan, Tiers and lower Brady formations and equivalents (Collinson et al. 1987;Forsyth 1987). ...
The remote lower reaches of the Rennick Glacier in the far north of Victoria Land hold some of the least-explored outcrop areas of the Transantarctic basin system. Following recent international field-work efforts in the Helliwell Hills, we here provide a comprehensive emendation to the regional stratigraphy. Results of geological and palaeontological reconnaissance and of petrographic, geochemical and palynostratigraphic analyses reveal a stack of three previously unknown sedimentary units in the study area: the Lower Triassic Van der Hoeven Formation (new unit, 115+ m thick) consists mainly of quartzose sandstone and non-carbonaceous mudstone rich in continental trace fossils. The Middle to Upper Triassic Helliwell Formation (new unit, 235 m thick) consists of coal-bearing overbank deposits and volcaniclastic sandstone and yielded typical plant fossils of the Gondwanan Dicroidium flora together with plant-bearing silicified peat. The succession is capped by c . 14 m of the sandstone-dominated Section Peak Formation (uppermost Triassic–Lower Jurassic). Our results enable more detailed correlation of the Palaeozoic–Mesozoic successions throughout East Antarctica and into Tasmania. Of particular interest is one section that spans the end-Permian mass extinction interval, which promises to allow detailed reconstructions of high-latitude vegetation dynamics across this critical interval in Earth history.
Supplementary material: A Supplementary Data File containing supplementary information, figures S1–S7, and additional references is available at https://doi.org/10.6084/m9.figshare.c.5118431
