Serpulid remains are very rare in the Lower Jurassic Hasle Formation of Bornholm, Denmark. A historical specimen mentioned, but not figured by Malling & Grön wall (1909) was reexamined and attributed to Pentaditrupa quinquesculcata and here f igured for the first time. New finds of additional well-preserved serpulid tubes are described as Serpula? alicecooperi sp. nov, which show adaptations for a lifestyle on fine-grained sediment in a nearshore environment.

We evaluate the influences of elevation and climate on the spatio-temporal distribution of wetland and dryland biomes during the Pennsylvanian and early Permian in tropical Pangea. The longstanding "upland model" places drought-tolerant vegetation in elevated habitats, where slope and drainage created moisture-limited substrates under a humid climate that simultaneously promoted peat accumulation in contemporaneous lowlands. Upland plants were periodically transported to, and buried in, lowlands. Rare preservation of dryland vegetation thus reflects its general absence in basins, and taphonomic vagaries of long-distance transport. The alternative "climate model" proposes that drought-tolerant plants dominated tropical habitats when climate was seasonally dry, with wetland vegetation reduced to scattered refugia. Environmental changes attending glacial-interglacial cycles caused alternating wetter-drier conditions, and the relative abundance of wetland versus dryland biomes in basinal lowlands thus varied with climatic oscillations. The paucity of drought-tolerant plants reflects a preservational megabias against habitats with seasonal moisture deficits. The environmental signal of "mixed" plant-fossil assemblages, comprising taxa characteristic of both wetland and dryland biomes, may help resolve these debates. We review key Pennsylvanian and lower Permian mixed assemblages from tropical Euramerican Pangea, and interpret their original habitats and climatic contexts based on multidisciplinary lines of evidence, including sedimentology, taphonomy, physiology, and paleoecology. Evaluations also consider patterns of vegetational distribution and taphonomy in modern tropical environments. We suggest that even a cursory view of current tropical plant distribution exposes flaws in the upland model. Where tropical climate is sufficiently humid to support peat swamps, slopes and elevated habitats do not host drought-tolerant vegetation, but are occupied by plants similar to those in lowland settings. This occurs because equable, high precipitation strongly dampens water-table variation across entire landscapes. Furthermore, taphonomic studies indicate that most plant-fossil assemblages record vegetation living near the burial site. Fossil floras thus reflect environmental conditions near their growth site, excluding an upland origin for most occurrences of droughttolerant taxa. Conversely, the climate model is consistent with modern tropical vegetational distribution and soundly explains late Paleozoic floristic patterns. When Pangean tropical lowlands experienced seasonally dry conditions, plants tolerant of moisture deficits dominated most habitats, whereas wetland vegetation was restricted to wetter sites with greater preservation potential. This occurred because topographic variations are magnified under seasonal precipitation regimes, creating a complex habitat mosaic with wetland patches in a landscape subject to seasonal drought. Accordingly, we propose that a macrofloral assemblage with even rare drought-tolerant taxa indicates seasonality in the broader landscape. At larger spatio-temporal scales, disagreement also persists about whether tectonic uplift or long-term climatic drying was the primary driver of changes in late Paleozoic floristic patterns and areal extent of tropical peat swamps. We argue that tectonic activity alone cannot explain the drastic reduction in peat swamps or coincident changes in dominance-diversity of wetland vegetation. Rates of plant dispersal and evolution far outpace that of mountain building, and peat-forming wetlands persisted in elevated habitats well into the Late Pennsylvanian. Therefore, progressive late Paleozoic aridification was the most probable driver of changing floral patterns and the distribution of wetland and dryland biomes in tropical Pangea. (C) 2021 Elsevier Masson SAS. All rights reserved.

Six late Atokan (early Asturian) floras from seasonally dry environments are described and quantitatively analysed from adpressions and palynomorphs. Collections are from the eastern margin of the Illinois Basin, USA, in an 80 km N-S transect. Plant fossils occur in sedimentary rocks below the underclay (paleosol) of the Minshall-Buffaloville Coal Member (thus, not “roof-shale” assemblages), uppermost Brazil Formation. Growth of floras under season dryness is indicated by outcrop and lithological features that suggest deposition in flashy discharge streams, including intraformational conglomerates, plant fossils that cross bedding planes indicating rapid, episodic burial, and local rhythmically laminated sediments. Common charcoal clasts are consistent with seasonal climate. Cordaitalean foliage dominates the macroflora, accompanied by the dryland elements Lesleya sp., Taeniopteris sp. cf. T. multinervia, and Sphenopteridium sp. Two unusual forms of foliage are presumed to be rare or novel dryland species. Small numbers of wetland/periwetland taxa include calamitaleans, Linopteris neuropteroides, Karinopteris/Eusphenopteris sp., marattialean fern foliage, Senftenbergia plumosa, cf. Zeilleria avoldensis and Sphenopteris sp. The palynoflora is dominated by marattialean tree ferns, wetland plants with broad dispersal capacities and environmental tolerances. Subdominant elements also have strong wetland affinities. Palynoflora-macroflora mismatches may reflect primary ecology, palynomorph reworking, or both. The occurrence of these floras near the Atokan-Desmoinesian (~ Bolsovian-Asturian) boundary coincides with an array of physical and geochemical data that indicate change from weak rainfall seasonality to marked seasonality at all phases of glacial-interglacial cycles, reflected prominently in the stratigraphic record from the localities studied.

The Late Mississippian and Pennsylvanian have been referred to as the Coal Age due to enormous paleotropical peat accumulations (coal beds). Numerous fossil floras have been collected from these coals, and their associated seat-earth paleosols and roof-shales, over more than two centuries, leading to the inference of vast swampy wetlands covering the Pangean tropics during the Pennsylvanian. In contrast, the Permian tropics are characterized as more arid, with sparser and more heterogeneous vegetation than inferred for the Pennsylvanian. In the tropics, the Pennsylvanian to Permian transition has been described as a changeover from a pteridophyte-dominated “Paleophytic flora”, to a seed-plant dominated “Mesophytic flora. This view notwithstanding, floras dominated by xeromorphic seed plants also are well known from the Pennsylvanian tropics. Some authors have characterized these plants as being occupants of uplands, subsequently transported into basinal-lowland, preservational environments. In this model, uplands are well drained, causing areas of drought under otherwise everwet climates. In this paper, we present an alternative interpretation: that the apparent transition in Pennsylvanian-Permian tropical vegetation reflects two types of taphonomic megabias. First is a preservational megabias, strongly favoring the vegetation of humid climates over that of seasonally dry climates. Accordingly, tropical-plant preservational potential fluctuated in concert with Late Paleozoic Ice Age glacial-interglacial oscillations, and contemporaneous sea-level and climatic changes. Second is an analytical megabias, strongly favoring the discovery and collection of the wetland biome from Pennsylvanian strata, overlooking the less frequently and more poorly preserved drought-tolerant biome. By Permian times, vast wetlands, and their fossil record, had largely disappeared from central Pangea (although continuing in Cathaysia), making drought-tolerant vegetation more “visible” to searchers, without changing its preservational circumstances. We demonstrate that the upland model is untenable, being inconsistent with the principles of plant biogeography and with geological aspects of the fossil record.

Premise of research. Sphenophytes are a modestly diverse lineage of vascular plants with a persistent record extending from the late Paleozoic to the present. However, patterns of arthropod herbivory on sphenophytes are poorly known because of a scattered literature, which we address in this report.Methodology. We document the 315-million-year-long record of sphenophyte-arthropod herbivory by focusing on the bookends of that record—namely, the Pennsylvanian and the present day. We add to this milieu a gall association on a newly described sphenophyte from the Upper Pennsylvanian of Portugal.Pivotal results. Earliest-known sphenophyte herbivory is Early Pennsylvanian, when virtually all interactions involved piercing-and-sucking damage by stylate insect mouthparts and lesions from cutting-and-slicing ovipositors. An exception is a newly discovered calamitalean (Annularia paisii sp. nov.) that harbored a newly discovered insect-induced gall (Paleogallus carpannularites ichnosp. nov.) that is similar to a modern fern gall. This discovery suggests that Late Pennsylvanian interactions were more diverse than previously suspected. By the end of the Pennsylvanian, the component community of one whole-plant calamitalean species had 12 damage types (DTs), only one of which was nonpuncturing damage. Shifts to external foliage feeding, mining, and galling are evident during the Late Triassic. A Middle Jurassic renewal of interactions was followed by a decrease in documented DTs present in the Cretaceous and Cenozoic. Fifteen modern species of the genus Equisetum, the sole surviving sphenophyte lineage, exhibit four herbivory patterns. First, almost all documented herbivory is confined to the seven species of Equisetum (horsetails), not subgenus Hippochaete (scouring rushes). Second, there are diversification events of four genera of herbivores—a beetle, two sawflies, and a fly—on subgenus Equisetum. Third, this arthropod herbivory is approximately evenly split among monophagy, oligophagy, and polyphagy. Fourth, the herbivore component community of Equisetum arvense L. (field horsetail) is diverse, representing 10 major feeding modes, comparable to a modern angiosperm species; there are considerably more feeding modes for E. arvense than there are for Pennsylvanian calamitaleans.Conclusions. Pennsylvanian sphenophytes supported few folivores, and there was a major shift in the modes of sphenophyte herbivory after the Paleozoic. Considerable modern herbivory is localized on E. arvense.

A macrofloral assemblage dominated by elements of the Euramerican dryland biome is described from the Brazil Formation in Clay County, Indiana (Illinois Basin). Fossils were recovered from a thin heterolithic unit between a shallow-marine bed and the paleosol beneath the Minshall Coal, a Middle Pennsylvanian succession deposited near the Atokan-Desmoinesian and Bolsovian-Asturian boundaries. Sedimentological indicators imply accumulation under a seasonal climate, including interbedded siltstone and sandstone deposited during flashfloods, intraclasts eroded from local sources, and charcoal produced by wildfires. The macrofloral assemblage is consistent with a dryland setting, being dominated by large, coriaceous gymnosperm leaves with mesic to xeric traits, including Cordaites spp. indet., Lesleya sp. indet., and Taeniopteris sp. cf. T. multinervia. Sphenopsids and ferns typical of the wetland biome are rare. In contrast, the microfloral assemblage is dominated by fern spores, with lesser lycopsid spores and cordaitalean pollen. The succession indicates that the dryland biome predominated during late regression, prior to the onset of perhumid conditions that resulted in peat accumulation at late lowstand. However, the abundance of palynomorphs from wetland vegetation implies gradual fragmentation of the prevailing dryland flora and replacement by the wetland biome in the transition to glacial maximum. The taphonomic and paleobiogeographic context confirms that floras adapted to seasonal moisture deficit periodically dispersed into tropical lowlands, rather than being transported from extrabasinal' or upland' environments. The precocious occurrence of Taeniopteris, more typical of Late Pennsylvanian and Permian floras, may be the earliest record of the fossil-genus, and exemplifies the association of derived plant taxa with dryland habitats. The predominance of broad-leaved gymnosperms with mesic to xeric characters suggests that dryland communities contained more slow-growing and long-lived plants than contemporaneous wetland floras.

Taxonomic analysis is provided for a Middle Pennsylvanian macrofloral assemblage collected from clastic wetland deposits in Clay County, Indiana, on the eastern margin of the Illinois Basin. Adpressed plant fossils were recovered from four distinct beds in the lowermost Staunton Formation, positioned above the Minshall Coal (uppermost Brazil Formation), part of a succession deposited near the Atokan-Desmoinesian boundary. The assemblage of 22 fossil-taxa is dominated by pteridosperms (including Neuropteris flexuosa, Macroneuropteris scheuchzeri, Alethopteris densinervosa, Neuropteris ovata, Eusphenopteris neuropteroides, and Neuropteris missouriensis) with lesser cordaitaleans (Cordaites spp. indet.) and sphenopsids (particularly Sphenophyllum cuneifolium). Lycopsids are uncommon, and ferns are rare. In contrast, the microfloral assemblage from the Minshall Coal and overlying clastic units is dominated by lycopsid and tree fern spores. Comparisons with established biozonation schemes yield different ages depending on the regional biostratigraphic framework used: (1) latest Bolsovian (Radiizonates difformis Biozone, American microfloras); (2) latest Bolsovian or earliest Asturian ('Neuropteris' rarinervis Biozone, Appalachian Basin macrofloras); or (3) earliest Asturian (Linopteris obliqua Biozone, European macrofloras). The placement and correlation of the Bolsovian-Asturian and Atokan-Desmoinesian boundaries, which have traditionally been equated by palynology, are evaluated in the context of this discordance. Several revised stratigraphic scenarios are proposed for this interval in the Illinois Basin, which is being increasingly recognized as a time of significant environmental change throughout Euramerica. Homotaxial comparisons with European macrofloral assemblages indicate that, of the 18 biological taxa recorded, between 14 and 17 (78-94%) also are common in coeval wetland deposits in Europe. The similarities exemplify the spatial conservatism and low diversity of wetland plant communities over vast areas of tropical Euramerica, a manifestation of the intrinsically stressful conditions that characterize such habitats, and indicates that neither the Laurentian Shield nor the Appalachian-Variscan Mountains were an insurmountable barrier to plant dispersal during the Middle Pennsylvanian.

A taxonomic, quantitative, and biostratigraphic analysis is presented for a macrofloral assemblage collected from below the Rock Island (No. 1) Coal Member at the historical Friendship Farm locality in Rock Island County, on the northwestern margin of the Illinois Basin. The Middle Pennsylvanian (middle Moscovian) fossiliferous strata involve the middle Tradewater Formation, and are situated a short distance below the Atokan–Desmoinesian Stage boundary as defined by marine microfossils and palynology. The assemblage of 14 fossil-taxa is overwhelmingly dominated by pteridosperms, including Laveineopteris rarinervis, Neuropteris flexuosa, Alethopteris serlii, Macroneuropteris scheuchzeri, and Mariopteris nervosa, whereas lycopsids, sphenopsids, and ferns are comparatively rare. Homotaxial comparison with the macrofloral biozonation scheme established in Europe indicates an Asturian age for the assemblage, in all likelihood early Asturian (Linopteris obliqua Biozone). Similar comparisons with range limits documented in the Appalachian Basin yield a more ambiguous age, but an early Asturian age is equally probable. These findings indicate that the Bolsovian–Asturian Substage boundary of western Europe lies below the Atokan–Desmoinesian Stage boundary in the Illinois Basin, boundaries that have traditionally been correlated by palynology. The Middle Pennsylvanian interval near these boundaries is being increasingly recognized as one of significant environmental change, reflected in marked lithological and biological modifications throughout tropical Euramerica. However, the fact that the Bolsovian–Asturian and Atokan–Desmoinesian boundaries are not synchronous, albeit being broadly equivalent, suggests that the environmental perturbation was a protracted event that may have had global consequences.

We document the occurrence of a marine bed, and its associated biota, in the Lower Pennsylvanian (Langsettian) Tynemouth Creek Formation of New Brunswick, and discuss its implications for paleogeography, stratigraphy, and paleoecology. This is only the second marine interval found in the entire Pennsylvanian fill of the Maritimes Basin of Canada, the other being recently found in the broadly same-age Joggins Formation of Nova Scotia. Evidence for the new marine transgression comprises an echinoderm-rich limestone that infills irregularities on a vertic paleosol surface within the distal facies of a syntectonic fluvial megafan formed under a seasonally dry tropical climate. Gray, platy ostracod-rich shales and wave-rippled sandstone beds that directly overlie the marine limestone contain trace fossils characteristic of the Mermia Ichnofacies, upright woody trees, and adpressed megafloras. This association represents bay-fills fringed by freshwater coastal forests dominated by pteridosperms, cordaites, and other enigmatic plants traditionally attributed to dryland/upland habitats. The fossil site demonstrates that marine transgressions extended farther into the interior of Pangea than has previously been documented, and may allow correlation of the Tynemouth Creek and Joggins Formations with broadly coeval European successions near the level of the Gastrioceras subcrenatum and G. listeri marine bands. It also helps explain the close similarity of faunas between the Maritimes Basin and other paleotropical basins, if transgressions facilitated migration of marine taxa into the continental interior.

We report Skolithos, Scoyenia and Mermia Ichnofacies from sub-humid tropical fluvial megafan deposits in the Lower Pennsylvanian Tynemouth Creek Formation of New Brunswick, Canada, and discuss their evolutionary and palaeoecological implications, especially regarding the colonization of continental freshwater/terrestrial environments. The Skolithos Ichnofacies comprises annelid/arthropod spreite in the upper storey of a fluvial channel. The Scoyenia Ichnofacies comprises tetrapod tracks, arthropleurid trackways, and shallow annelid/arthropod burrows in active/abandoned fluvial channels and rapidly aggrading levees/splays in proximal interfluve areas. The Mermia Ichnofacies comprises abundant xiphosuran trackways, along with diverse traces of other arthropods, annelids, mollusks, and fish, in shallow freshwater lakes, ponds, and coastal bays in slowly aggrading distal interfluve areas. Transitional Mermia/Scoyenia Ichnofacies comprise tetrapod, mollusk and annelid/arthropod traces in coastal bay deposits on the distal edge of the megafan. These trace fossil suites (1) provide the clearest documentation yet of the mid-Carboniferous diversification event, when tropical continental environments became more densely populated; (2) suggest that euryhaline visitors (xiphosurans, microconchids, and other taxa) from open marine settings played a key role in this episode of freshwater colonization; and (3) provide empirical support for the "Déjà vu Effect", the evolutionary concept that new or empty ecospace, recurrent in spatially and temporally variable environments, is colonized by simple ichnocoenoses.

Riparian vegetation profoundly influences modern fluvial channels in a variety of ways, depending on the life-history strategies of different plant types, disturbance frequency, and drainage conditions of available habitats. Direct evidence for these dynamic relationships is usually cryptic in ancient deposits. We report evidence for interactions between rivers and in situ vegetation for selected sites in the lower Pennsylvanian Joggins Formation of Atlantic Canada, encompassing fixed, meandering, and distributary channels originally up to 6 m deep. Channel bodies are associated with a suite of fossilized plant remains, specifically lycopsids that preferred stable wetland settings, disturbance-tolerant calamitaleans, and slow-growing, long-lived cordaitaleans.Vegetation was effective in stabilizing banks and bars and promoting aggradation. Lycopsids and calamitalean groves colonized the channel bed during periods of reduced flow, drawing on the groundwater table, and mounds around upright trunks indicate that they formed bar nuclei after flow resumed. Bank-attached bars with lateral-accretion sets contain upright trees, which may have stabilized inclined sediment surfaces, and trees present between small distributary channels may have formed vegetated islands. Erect lycopsids rooted below the channel base project up into the channel fill, where they formed obstacles and nucleated sediment mounds in active channels. On channel cutbanks, upright lycopsids are tilted towards the channel, and early formed rhizoconcretions are associated with deep cordaitalean root systems in the tops of channel fills. These features imply that vegetation contributed to stabilization of sediment surfaces. The predominance of in situ over transported plant remains suggests that these low-flow-strength rivers had limited ability to erode and entrain large woody debris, especially for small channels with strengthened banks.We infer that patterns of interaction between vegetation and rivers with a range of fluvial style broadly resembled those of today. By the early Pennsylvanian, rivers had moved from a geomorphic and biogeomorphic mode of operation into a fully ecological mode with prominent feedback loops between vegetation and fluvial processes. Vegetation is commonly poorly preserved in fluvial systems but should be incorporated into facies models for Pennsylvanian and younger strata, possibly also for some Devonian and Mississippian formations.

The 1125-m-thick type section of the Pennsylvanian Boss Point Formation is well exposed along the shore of the Bay of Fundy in Nova Scotia. We provide the first comprehensive account of the entirety of this formation, which comprises nearly one-third of the stratigraphic thickness of the Joggins Fossil Cliffs UNESCO World Heritage Site. The basal Chignecto Bay Member (0–91.5 m) is composed of redbeds, single-storey channel bodies with northerly paleoflow, and thin palustrine limestones. The middle Ward Point Member (91.5–951.7 m) contains up to 16 megacycles composed of alternations between thick packages of braided fluvial sandstone and fine-grained deposits. Although regional studies of the Boss Point Formation suggest that the fine-grained deposits are largely composed of lacustrine sediments, these intervals consist largely of poorly drained and well-drained floodplain deposits in the type section. The facies variations and southeast-directed paleoflow in the Ward Point Member record modest uplift associated with the growth of the salt-cored Minudie Anticline. The North Reef Member (951.7–1125 m) is composed of redbeds and two distinctive multistorey channel bodies. This uppermost member records a shift to more arid, oxidizing conditions, was the precursor to a major phase of salt withdrawal, and represents a transition to the overlying Little River Formation. The sedimentological framework, revised stratigraphy, and detailed measured section and map will provide a foundation for future study of this remarkable Pennsylvanian exposure.

Vegetation is a major driver of fluvial dynamics in modern rivers, but few facies models incorporate its influence. This article partially fills that gap by documenting the stratigraphy, architecture and palaeobotany of the Lower Pennsylvanian Boss Point Formation of Atlantic Canada, which contains some of the Earth's earliest accumulations of large woody debris. Braided‐fluvial systems occupied channel belts of varied scale within valleys several tens of metres deep and more than 12 km wide, and their deposits predominantly consist of sandy and gravelly bedforms with subordinate accretionary macroforms, high flow‐strength sand sheets and rippled abandonment facies. Discrete accumulations of clastic detritus and woody debris are up to 6 m thick and constitute at least 18% of the in‐channel deposits; they represent lags at the base of large and small channels, fills of minor channels and sandy macroforms that developed in central positions in the upper parts of channel fills. Sandstones with roots and other remnants of in situ vegetation demonstrate that vegetated islands were present, and the abundance of discrete channel fills suggests that the formation represents an anabranching, island‐braided sandbed river, the earliest example documented to date. Although some sphenopsid and lycopsid remains are present, most woody fragments are derived from cordaitalean trees, and the evolution of this group late in the Mississippian is inferred to have exerted a significant influence on fluvial morphodynamic patterns. The formation records a landscape in which active channel belts alternated with well‐drained floodplains colonized by dense, mature forests and local patches of pioneering, disturbance‐tolerant vegetation. Lakes and poorly drained floodplains dominated by carbonate and organic deposition, respectively, were also present. A large supply of woody debris triggered channel blockage and avulsion, and active channel margins and islands within the channel belts were initially colonized by pioneer vegetation and subsequently stabilized by large trees. A similar alternation of stable and unstable conditions is observed in modern braided rivers actively influenced by vegetation.

The distribution and community ecology of Early Pennsylvanian (middle Bashkirian, Langsettian) vegetation on a seasonally dry fluvial megafan is reconstructed from plant assemblages in the Tynemouth Creek Formation of New Brunswick, Canada. The principal motif of the redbed-dominated succession consists of degraded interfluve surfaces overlain by coarsening-upward aggradational sequences, a pattern that expresses the approach of an active channel system over a part of the megafan where landscape stasis prevailed. Accrual under a (dry) subhumid tropical climate, typified by a protracted dry season and a short wet season with torrential rainfall, resulted in Vertisol-like paleosols, episodic discharge and sedimentation, shallow channels incised into partially indurated interfluve strata, and scattered ‘waterhole’ deposits. Plant fossils, including many upright stumps, are preferentially preserved above paleosol-mantled interfluve surfaces, recording the inundation of a vegetated landscape. Quantitative analysis of 41 census-sampled megafloral assemblages collected in facies context indicates that a cordaitalean-rich flora dominated the dryland ecosystem. Less common was a wetland flora typical of tropical lowlands at coeval localities, comprising medullosalean pteridosperms and calamitaleans with rare ferns and lycopsids. ‘Enigmatic dryland’ plants, taxa of ambiguous affinity including Megalopteris, Pseudadiantites, and Palaeopteridium, were rare but surprisingly diverse. The taphonomic and sedimentologic context of fossiliferous horizons indicates that low-diversity, old-growth stands of gigantic cordaitaleans blanketed distal interfluves and inactive parts of the megafan, environs marked by limited deposition and extended paleosol development. Small patches of the pteridosperm-dominated wetland flora were interspersed within the dense cordaitalean forest, restricted to landforms that acted as waterholes during the dry season, such as perennial lakes, stagnant ponds, and seasonally active interfluve channels. In contrast, cordaitaleans and wetland plants formed mixed communities in disturbance-prone proximal interfluves and fluvial tracts, where more flooding and sedimentation resulted in less moisture-stressed conditions and a wider range of habitable landforms. Dense calamitalean groves persisted alongside fluvial channels, and an array of wetland plants occupied seasonally active abandoned channels that retained water throughout the year (waterholes). Rare ‘enigmatic dryland’ species were more prevalent in flood-prone fluvial tracts, and were dispersed within cordaitalean-dominated and wetland communities rather than forming discrete, compositionally unique patches. Although frequently characterized as ‘extrabasinal’ or ‘upland’ elements, this study confirms that these unusual plants occupied Pennsylvanian tropical lowlands during episodes of climatic drying.

As vegetation evolved during the Palaeozoic Era, terrestrial landscapes were substantially transformed, especially during the ∼120 million year interval from the Devonian through the Carboniferous. Early Palaeozoic river systems were of sheet-braided style – broad, shallow, sandbed rivers with non-cohesive and readily eroded banks. Under the influence of evolving roots and trees that stabilised banks and added large woody debris to channels, a range of new fluvial planform and architectural styles came to prominence, including channelled- and island-braided systems, meandering and anabranching systems, and stable muddy floodplains. River systems co-evolved with plants and animals, generating new ecospace that we infer would have promoted biological evolution. By the end of the Carboniferous, most landforms characteristic of modern fluvial systems were in existence.