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5. Ordovician palaeocontinental reconstructions plotting palaeogeographical distribution of dispersed spores. Data from Appendix 1.
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A database of all reported Ordovician–Silurian land plant megafossil and dispersed spore assemblages has been assembled. For each assemblage a list of taxa has been prepared and its location plotted on new palaeocontinental reconstructions. These new data compilations are analysed with respect to palaeophytogeographical differentiation and various...
Citations
... 419-359 Ma) was arguably the most crucial chapter in the evolution of Earth's land biosphere. Non-marine environments at the end of the preceding Silurian Period accommodated nascent invertebrate communities in near-water settings (e.g., Davies et al., 2006;Morrissey et al., 2012a;Shillito and Davies, 2017;Wellman et al., 2023), witnessed frequent invasions of freshwater bodies by jawless fish (e.g., Boucot and Janis, 1983;Blom et al., 2001;Sallan et al., 2018), and hosted scattered stands of small, simple plants in coastal regions (e.g., Wellman et al., 2013;Gensel et al., 2020;Capel et al., 2022), but their equivalents sixty million years later were unrecognisable. By the end of the Devonian the range of permanent invertebrate habitats had expanded to even the driest nonmarine settings (e.g., Morrissey et al., 2012b;Minter et al., 2016;Buatois et al., 2022), ...
The evolution of trees and forests through the Devonian Period fundamentally changed Earth's land biosphere, as well as impacting physical environments and geomorphology by stabilizing sediment and interacting with flowing air and water. From the mid Givetian Age onwards, lignophyte flora are known to have been key parts of the machinery in the ‘Devonian Landscape Factory’, but the impact of earlier forests, dominated by less woody cladoxylopsids, are not as well understood. In this paper we report evidence for a previously unrecognized cladoxylopsid forest landscape, archived within the Eifelian Hangman Sandstone Formation of Somerset and Devon, SW England. This unit has previously been considered palaeobotanically depauperate but is here shown to contain the earliest fossil evidence for such trees in the British record, as well as the oldest known evidence globally for the relative position of standing trees: in common parlance a ‘fossil forest’. In addition to abundant fossil material attributable to the cladoxylopsid tree Calamophyton , and other early Middle Devonian flora, the sedimentary context of the plant remains sheds light on the biogeomorphic impacts of these earliest forests. The trees colonized a sizeable distributive fluvial system (DFS) that was prone to seasonal disturbance events. The nature of the sedimentary system has created a bias to those facies where biogeomorphic signatures are most frequently recorded (from the distal parts of the system), but across the DFS there is evidence of plant-sediment interactions in the form of vegetation-induced sedimentary structures, rooting features, and accumulations of plant debris. Plant remains are also found in nearshore facies adjacent to the DFS, attesting to the development of a novel non-marine/marine teleconnection from the production and export of new biological sedimentary particles. The Hangman Sandstone Formation is illustrative of the revolutionary power of cladoxylopsid trees as biogeomorphic agents, forming densely spaced forests and shedding exceptionally abundant plant debris, whilst also impacting local landforms and sediment accumulations and profoundly changing landform resilience against flood disturbance events. These findings provide evidence that the Eifelian Stage (393.3-387.7 Ma) marks the onset of tree-driven changes to physical environments that would forever change Earth's non-marine landscapes and biosphere.
Supplementary material: https://doi.org/10.6084/m9.figshare.c.7084873
... Plants are a critical element of life on the continents as we know it. Some authors have suggested that embryophytes (land plants) are monophyletic, that bryophytes and tracheophytes are sister clades based on critical molecular phylogenesis [1][2][3], and that land plants evolved from multicellular charophycean green algae [4][5][6]; surprisingly, recent theories emphasise the sister relationship of unicellular or filamentous Zygnematophyceae charophytes to land plants [7][8][9][10]. ...
... The first indirect evidence for early land plants are cryptospores [16], which occur as monads, dyads and permanent tetrads and were produced by a heterogeneous group called Eophytidae [17], former cryptosporophytes [18] and cryptophytes. The first hypothetical palynomorphs that might be interpreted as cryptospores were described in the Middle Cambrian [19], consistent with phylostratigraphic predictions of the possible emergence of crown embryophytes [20], and the last specimens are from the Middle Devonian [2,21,22]. True trilete spores represent vascular land plants and their immediate ancestors [11,23,24], and the oldest trilete spores are reported from the Ordovician [25,26]. The oldest undoubtedly known sporophyte of a vascular land plant is Cooksonia barrandei Libertín et al. [12] from the middle Sheinwoodian strata of the Perunica microplate (Peri-Gondwana; now the Czech Republic; [13]). ...
... The oldest undoubtedly known sporophyte of a vascular land plant is Cooksonia barrandei Libertín et al. [12] from the middle Sheinwoodian strata of the Perunica microplate (Peri-Gondwana; now the Czech Republic; [13]). Other important events are peaks of cryptospore abundance within the Hirnantian-Rhuddanian interval [2]. The first global event for the diversification of early land plants and the change from cryptospore to hilate/trilete spore dominance is palynologically documented (trilete spores) after the Homerian glaciation [2,15]. ...
This paper describes dispersed cryptospores and trilete spores from tropical, temperate and cool climate belts within Přídolí and compares them with the land plant megafossil record. The palynology of earlier intervals in the Silurian are also reviewed. A common feature of the cryptospore and trilete spore records is that their number is surprisingly lowest in the tropical climatic belt and much higher in the temperate and especially in the cool latitude, and the highest number of cryptospore taxa occurring only in one belt is found in the cool belt while the highest number of trilete spore taxa that occurred only in one belt is recorded in the temperate belt. In general, based on the dispersed spore record, we can estimate that the plant assemblages of the tropical belt were dominated by rhyniophytes; trimerophytes probably prevailed over rhyniophytes in the temperate belt, and rhyniophytes again dominated within the cool belt.
... Thus the spore-bearing inland exposures (which contain rare biota) can be directly correlated with the type section for the Stonehaven Group, which is better exposed along the coast and yields more abundant biota. The dispersed spore zonation scheme developed for the Silurian is based largely on investigations from the independently age-constrained type sections for the Llandovery, Wenlock and Ludlow Series (Burgess 1991;Burgess andRichardson 1991, 1995) and has subsequently been utilized throughout Avalonia, Laurentia and Baltica, and indeed worldwide, and shown to be highly reliable (Wellman et al. 2013). ...
... Confirmation of the age of the Stonehaven Group biota is hugely significant in terms of our understanding of the earliest terrestrial ecosystems. The dispersed spore assemblages are composed entirely of non-marine forms (dispersed spores and phytodebris) and represent an extremely rare example of a pre-Devonian spore assemblage from continental deposits (Wellman et al. 2013). Although associated sediments contain abundant plant fragments, plant axes are exceedingly rare and constitute diminutive axes, with a solitary bifurcating example, only millimetres in size (Fig. 4). ...
The basal upper Silurian-Lower Devonian ‘Lower Old Red Sandstone’ deposits of the Midland Valley of Scotland contain several important fossil biotas, including that from the Cowie Harbour Fish Bed. This biota is of great significance because it represents one of the oldest known examples of a fossilised terrestrial ecosystem and includes the oldest reported air-breathing land animal (the myriapod Pneumodesmus newmani Wilson & Anderson 2004). Based on biostratigraphical evidence from dispersed spores this biota is dated as late Wenlock (late Silurian) in age. Recently, however, this age constraint was challenged, based on ²³⁸ U- ²⁹⁶ Pb radiometric analysis of zircons, and it was proposed that these deposits are much younger (Early Devonian: Lochkovian). This proposal has serious implications regarding: (i) the composition and nature of early terrestrial ecosystems; (ii) the geological setting with respect to the timing of terrane accretion and the onset of ‘Lower Old Red Sandstone’ sedimentation. We report on newly discovered dispersed spore assemblages and additional zircon data that confirm a late Wenlock (late Silurian) age. This age designation establishes the importance of the biota of the Cowie Harbour Fish Bed and is more compatible with both its biotic composition and the regional geological setting.
... often embedded in marine lithologies and (b) associated there with marine life forms such as fish, trilobites, acritarches or graptoliths, which in turn are used as index fossils for a stratigraphic classification of the Cooksonia finds(EDWARDS & RICHARDSON 2004: 377 ff.; STANLEY 2001: 388 f.; cf. BODZIOCH et al. 2003; LIBERTÍN et al. 2018b LIBERTÍN et al. , 2018cWELLMAN et al. 2013). ...
English translation of the essay “Fossilien in Metamorphiten: Ein Rekonstruktionsversuch am Beispiel Anglmühle bei Rittsteig (Landkreis Cham)”, published in June 2022 in Nachrichtenblatt Freundeskreis der Geologischen Staatssammlung München e.V. (= “Bulletin of Friends of the Geological State Collection Munich e.V.”), Vol. 22./23.: 13–21. Metamorphic rocks were long thought to be devoid of fossils. This was especially true for the East Bavarian crystalline. In the 1980s, the geoscientist Dr. Erhard Reitz to extract a small number of Silurian plant spores from a biotite mica schist from Anglmühle near Rittsteig (Eastern Bavaria). This essay examines the possibilities of assigning some of these spores to a specific genus. Species considerations are also included, bringing cooksonoid plants into focus. In addition, aspects of stratigraphic classification and reconstructions of the paleo-environment are discussed.
... Ambitisporites tripapillatus was reported from the Wenlock to Ludlow of the UK; Wenlock to Pragian of Portugal [25] and Libya [26]; Přídolí of the UK, Libya [26] and Sweden [27]; and Pragian to early Emsian of Argentina [28]. Another Ambitisporites TAP species is A. eslae which was described from the Přídolí of Sweden [1], Algeria [29] and Libya [30]; late Pragian to early Emsian of Argentina [28]; lower Lochkovian of Brazil [31]; lower Lochkovian to lower Pragian of Spain [32][33][34]; Pragian of France [35]; and Pragian to Emsian of Saudi Arabia [36]. ...
... Ambitisporites tripapillatus was reported from the Wenlock to Ludlow of the UK; Wenlock to Pragian of Portugal [25] and Libya [26]; Přídolí of the UK, Libya [26] and Sweden [27]; and Pragian to early Emsian of Argentina [28]. Another Ambitisporites TAP species is A. eslae which was described from the Přídolí of Sweden [1], Algeria [29] and Libya [30]; late Pragian to early Emsian of Argentina [28]; lower Lochkovian of Brazil [31]; lower Lochkovian to lower Pragian of Spain [32][33][34]; Pragian of France [35]; and Pragian to Emsian of Saudi Arabia [36]. ...
... Synorisporites tripapillatus is another miospore species with TAP that occurs in the Přídolí of Argentina [37], Sweden [27], the UK, France and Algeria [26]; Ludlow of Spain [26]; and Dowtonian of UK [38]. ...
A new hypothesis about the origin of isoetalean lycopsids was proposed based on palynological data. The occurrence of three apical papillae on the proximal surfaces of miospores is a significant palynological feature that is clearly defined in both isoetalean and selaginellalean clades. Three apical papillae appeared for the first time within lower Silurian (Wenlockian ca. 430 My) and only in rhyniophytoid plants. Using this observation, we suggest that isoetalean lycopsids could have evolved directly from rhyniophytoids and not from protolepidodendralean lycopsids in the middle Devonian (Eifelian–Givetian) as previously suggested, because protolepidodendralean spores do not possess three apical papillae. Spores with three apical papillae, reported as dispersed as well as in situ, were recorded continuously from the lower Silurian (Wenlockian) through the Devonian, Carboniferous, Permian, Mesozoic to Cenozoic era and form a phylogenetically independent lineage
... In comparison to marine fossils, land-derived remains are better to reveal continent connections in that they would encounter bigger barriers on transoceanic dispersal (Steemans et al., 2010). The spatial distribution of dispersed spores from early land plants has been discussed (Steemans et al., 2010;Wellman et al., 2013), but none of these analyses took the Tarim records into consideration. Besides unclear paleogeographic positions of Tarim, this is largely because, we believe, spore assemblages reported from the Ordovician-Silurian of this paleoplate are rare or scarcely published on international journals. ...
... It is interesting to note that such zonation is not pronounced in previous analysis and there is a slight divergence between genus-and species-level results. Previous quantitative assessment shows that, the Llandovery assemblages of most paleoplates are close in composition to each other, except that those of South Africa and South China gather into an isolated cluster (Wellman et al., 2013). The causes of the divergence between our results and previous research probably involve two main factors: 1) the pre-grouping localities utilized in cluster analysis; 2) the basic database of dispersed spore records. ...
... The causes of the divergence between our results and previous research probably involve two main factors: 1) the pre-grouping localities utilized in cluster analysis; 2) the basic database of dispersed spore records. Unlike the previous practice (Wellman et al., 2013), here we use a relatively broader division of paleogeographic locality. In the first-order localities of our analyses, geographically close ones are pre-grouped as one unit instead of being considered as separate small localities. ...
The Tarim Plate, an independent continent during the Paleozoic, is of significance in understanding life and environment evolution, however, its paleogeography during the early Silurian is poorly known. Palynology, especially on land-derived palynomorphs, provides independent evidence for paleogeography as a supplement to paleomagnetic data. Here we recognize a Llandovery palynoflora from two sections (Arisu and East Dawangou) of the Kalpintag Formation in the northwestern Tarim Basin, Xinjiang, China, the paleontological evidence of which suggests that the Tarim Plate was proximal to western Gondwana during the early Silurian. The palynoflora consists of moderately diverse cryptospores with eight genera and twelve species, as represented by Laevolancis chibrikovae, Sphaerasaccus glabellus, Dyadospora murusdensa, Pseudodyadospora laevigata, P. petasus, and Tetrahedraletes medinensis. The monad S. glabellus reported herein is the first record from China. Other palynomorphs include a large number of sphaeromorph acritarchs, some tubes and cuticle-like sheets, and a few scolecodonts. The various kinds of meiosis process and predetermined diversity of older cryprospore producers in the Tarim Basin, together with ecological factors, contribute to the evolution of the Kalpintag cryptospore producers. By taxonomic comparisons of global coeval sporomorph records, combined with quantitative analyses (Cluster Analysis and Nonmetric Multidimensional Scaling Analysis), the Kalpintag palynoflora shows more closely related to those in northern Chad, northeastern Libya and central Saudi Arabia. The geographical zonation of sporomorph might emerge in the Llandovery. The geographical proximity of the Tarim Plate to western Gondwana during that time is also suggested.
... Molecular clock data favors a middle Cambrian to Early Ordovician origin of embryophytes (Donoghue et al., 2021), while palynologic evidence supports an origin of land plants from freshwater charophyte algae by at least the Early Ordovician Strother and Foster, 2021). The nascent land plants, although diminutive, simple, and of low diversity (Wellman et al., 2013), may have offer a new food resource and significantly contributed organic detritus to marginal-marine settings opening new opportunities to tolerant, generalist marine species. ...
Estuarine deposits of the Furongian Pico de Halcón Member of Argentina contain trace and body fossils that allow assessing the role of evolutionary and environmental factors on early colonization of marginal-marine environments. The outer region of the estuary was characterized by a subtidal sandbody flanked by tidal flats. Vertical burrows of suspension feeders and probably passive predators are abundant in the high-energy areas of the outer estuary. Horizontal trilobite and vermiform trace fossils record the activities of mobile deposit, detritus, and suspension feeders in more protected settings. Arthropod trackways, vertical burrows, and horizontal vermiform burrows have been recorded in middle estuarine deposits. The occurrence of trackways attests the ability of some late Cambrian marine arthropods to periodically migrate inland following tidal channels or via salt-water wedges. No trace and body fossils have been found in inner valley areas. Outer and middle estuarine deposits contain the trilobite Neoparabolina frequens argentina. Its record in brackish-water settings is envisaged as a result of its generalist nature and ability (physiologic or behavioral) to cope with a wide array of conditions, flexible resource requirements, and successful spreading.
Although trace-fossil distribution along the salinity gradient reflects the basics of the “brackish-water model”, the remarkably low ichnodiversity in the middle estuary and the lack of trace fossils in the inner estuary are interpreted as reflecting evolutionary controls. Teichichnus assemblages, forming monospecific occurrences or with Planolites, in fine-grained, heterolithic facies seem to be remarkably persistent through geologic time. The studied trace fossils yield insights on attempts of some clades to expand into stressful brackish-water settings early in their evolutionary histories. In addition, comparison of the environmental tolerance of the Furongian benthos with other occurrences in younger early Paleozoic estuarine settings allows to track early steps of the colonization of brackish-water environments as it developed during the Ordovician Radiation.
... In addition to the different biodiversity curves for marine invertebrates, Fig. 2E also displays the diversification of the earliest land plants, illustrated by the genus-level diversity of fossil land-plant derived spores , based on data from Wellman et al., 2013 andCascales-Miñana, 2016). The radiation of land-plants occurred about 100 myr after the initial radiation of marine invertebrates, with an Ordovician 'explosion' of miospore diversity, that resembles a rather normal, progressive radiation (e.g., Gerrienne et al., 2016). ...
... E, total (red line) and normalized (sensuCooper, 2004; blue line) land plant derived spore diversity pattern, redrawn fromServais et al. (2019, fig. 4a), based on data fromWellman et al. (2013) andCascales- Miñana (2016). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)(1993). ...
... The rise of plants can be traced via fossil spores preserved in the geological record by these early terrestrial plants. Although traces of early land plants have been recorded from successions as old as the Ordovician (Rubinstein et al. 2011;Badawy et al. 2014;Rubinstein and Vajda 2019;Leslie et al. 2021), a major radiation occurred during the late Silurian and Early Devonian, when plants developed more complex forms, increased in abundance, and became well established on most continents (Gray et al. 1974;Richardson and McGregor 1986;Mehlqvist et al. 2012Mehlqvist et al. , 2014Mehlqvist et al. , 2015Wellman et al. 2013Wellman et al. , 2022Leslie et al. 2021). This was also a time when other groups of organisms developed in the terrestrial realm and left behind peculiar fossil remains. ...
The enigmatic fossil Prototaxites found in successions ranging from the Middle Ordovician to the Upper Devonian was originally described as having conifer affinity. The current debate, however, suggests that they probably represent gigantic algal–fungal symbioses. Our re-investigation of permineralized Prototaxites specimens from two localities, the Heider quarry in Germany and the Bordeaux quarry in Canada, reveals striking anatomical similarities with modern fungal rhizomorphs Armillaria mellea. We analysed extant fungal rhizomorphs and fossil Prototaxites through light microscopy of their anatomy, Fourier transform infrared spectroscopy, X-ray microscopy, and Raman spectroscopy. Based on these comparisons, we interpret the Prototaxites as fungi. The detailed preservation of cell walls and possible organelles seen in transverse sections of Prototaxites reveal that fossilization initiated while the organism was alive, inhibiting the collapse of delicate cellular structures. Prototaxites has been interpreted to grow vertically by many previous workers. Here we propose an alternative view that Prototaxites represents a complex hyphal aggregation (rhizomorph) that may have grown horizontally similar to modern complex aggregated mycelial growth forms, such as cords and rhizomorphs. Their main function was possibly to redistribute water and nutrition from nutrient-rich to nutrient-poor areas facilitating the expansion for early land plant communities.
... More succinct reviews, not summarized below, are those from Zigaite and Blieck (2013), who reviewed the data on the first Early Paleozoic vertebrates. The first palaeophytogeographical maps, i.e. distribution patterns of land plants, were proposed by Wellman et al. (2013). One of the key fossil groups for Ordovician biostratigraphy, the conodonts, that have been well studied in the Ordovician since the 1950s, were absent in the synthesis compiled by Harper and Servais (2013), unfortunately. ...
Due to increasing availability of data for many fossil groups and a generally accepted palaeogeographical configuration, palaeontologists have been able to develop progressively more robust palaeobiogeographical scenarios for the spatial distributions of Ordovician marine faunas. However, most research in Early Palaeozoic palaeobiogeography centers on data derived from extensively studied localities in North America and Europe. Thus, clear patterns are emerging of regional biogeography for these areas. However, the fragmentary nature of data from other regions hinders the development of a detailed understanding of palaeogeographical schemes of many clades at the global level. Provincial patterns are now available for several fossil groups, but the global coverage remains generally fragmentary. Palaeobiogeographical investigations were traditionally focused on the better understanding of palaeogeographical scenarios and often employed quantitative analyses of faunal similarity. More recently palaeobiogeographical analyses have expanded to investigate questions such as the location and pace of speciation and macroevolution together with macroecological change. For example, studies on the evolution of speciation levels in the frame of the taxonomic radiation of the Great Ordovician Biodiversification are now available. Future investigations, including modelling, will provide more integrative, global patterns of provincialism, including the location of Ordovician biodiversity hotspots and the recognition of latitudinal diversity gradients.
