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Premise of research. Cheirostrobus pettycurensis Scott is an early Carboniferous sphenophyte known only from its anatomically preserved strobili, which bear highly dissected "sporophylls" comprising a lower vegetative part and an upper fertile part bearing inwardly facing sporangia. Since Scott's pioneering work over 100 years ago, the genus has not been reinvestigated such that it remains poorly characterized and its systematic position enigmatic. We reinvestigate Cheirostrobus , providing new insights into its structure, anatomy, and in situ spores and thereby addressing long-standing questions concerning its considerable systematic and evolutionary importance. Methodology. Historically prepared slides of Cheirostrobus from museum collections were examined using transmitted light microscopy to facilitate a detailed description using modern terminology, allowing for more effective comparisons and interpretations. Pivotal results. The strobilus axis comprises a stellate protostele with 9–13 protoxylem poles showing exarch maturation. The protoxylem has circular and metaxylem scalariform pitting. The main vascular bundles depart from the stele in superposed whorls and divide vertically close to the cortex, from which the lower (abaxial) daughter bundle supplies two or three bracts and the upper (adaxial) daughter bundle supplies two or three sporangiophores, with each bract subtending one sporangiophore. Individual sporangiophores have a foliar apex and typically bear four inwardly facing, longitudinally elongated sporangia disposed in two vertical rows. In situ spores are homosporous and trilete, have a prominent margo with leavigate exine, and range from 48 to 77 μm in diameter. Spores conform to the sporae dispersae Retusotriletes incohatus Sullivan 1964. Conclusions. Cheirostrobus has an organization similar to members of the Sphenophyllales and the Calamitales; it is interpreted as a member of the Sphenophyllales that is on the evolutionary stem lineage leading to the stratigraphically younger Calamitaceae. Retusotriletes -type spores are reported in situ for the first time within sphenophytes, having previously been found within rhyniophytes, zosterophylls, trimerophytes, and algae, further emphasizing the polyphletic nature of the genus and convergent spore evolution across multiple lineages. Retusotriletes incohatus in the dispersed record ranges from the late Famennian (Devonian) to the late Viséan (Carboniferous) and is common in basal Carboniferous deposits, suggesting that Cheirostrobus (or closely related plants producing the same kind of spores) had a longer stratigraphic range than was previously recognized and an earliest Carboniferous acme. [ABSTRACT FROM AUTHOR]

Continuing palaeofloristic studies in the Northern Tocantins Fossil Forest, we describe two new calamitalean species from the Permian of the Parnaíba Basin (central-north Brazil). The fossils comprise axes of various sizes, preserved anatomically as siliceous petrifactions, and found in highly mature sandy fluvial deposits of the Motuca Formation. Based on anatomical and morphological characteristics, Arthropitys tocantinensis sp. nov. and Arthropitys barthelii sp. nov. are described. They share a small central pith cavity (extremely reduced in the latter), scalariform tracheid pitting, and prominent pitting of the ray parenchyma. However, they differ markedly in their branching system: the former having 3–12 branches per node either with or lacking secondary growth, the latter showing 2–17 branches without any secondary growth. However, in A . tocantinensis sp. nov., the presence of large woody branches supports a more complex architecture with at least three successive orders of branches. The extensive secondary tissue in both species is homogeneous; clear segmentation is only visible in the proximal wood of A . tocantinensis sp. nov., but completely absent in A . barthelii sp. nov. The growth architecture of these upright growing, self-supporting trunks are reconstructed based on sizable transverse and longitudinal preparations. Our results confirm that thick woody calamitaleans were elements of disturbed riparian vegetation and much more diverse in terms of anatomy and branching patterns than previously thought. They were well adapted to seasonally dry conditions and formed major plant constituents of Permian low-latitude Southern Hemisphere communities. Additionally, we report the first evidence of colonisation on arborescent calamitaleans by herbaceous sphenophyte axes from the Permian. One of the Arthropitys stems hosts at least 30 Sphenophyllum shoots of various ontogenetic stages, growing inside the destroyed pith, which was previously excavated by arthropod boring. Based on the distribution of key genera within late Paleozoic floras of Euramerica, Gondwana and Cathaysia floral realms cluster analysis and Jaccard Coefficient highlight the distribution of a “Mid-North Brazilian” phytogeographic Region during the early Permian. [ABSTRACT FROM AUTHOR]

New sphenophyte stems from the Permian of the Parnaíba Basin (central-north Brazil) are described in detail and assigned to Arthropitys , a genus that was recognised from the Euramerican and Cathaysian floristic provinces. The fossil material is reported from the Permian Motuca Formation in northern Tocantins and was discovered in fluvial deposits, which originated under seasonal conditions in a widely distributed alluvial plain environment. The silica-petrified specimens are three-dimensionally preserved and provide considerable information on histological and developmental details not previously observed in the genus. The stems show very regular branch traces, attached branches or basal branching stumps. Based on their anatomical and morphological characteristics two new species are described: Arthropitys isoramis sp. nov. and Arthropitys iannuzzii sp. nov. One specimen of A. isoramis sp. nov. shows several woody roots attached to the basal region of the stem. This record differs radically from traditional and largely generalised reconstructions of calamitaleans, which are largely understood as rhizomatous trees based on inferences with extant Equisetum. The new sizable finds underline the high potential of northern Tocantins as a widely extended fossil lagerstätte that significantly enlarges our understanding of extinct low-latitude Southern Hemisphere floral communities. [ABSTRACT FROM AUTHOR]

A new petrified calamitalean is described from the Permian Motuca Formation, Parnaíba Basin, central-north Brazil. In contrast to all other three-dimensionally preserved Brazilian species, it represents a semi-self-supporting woody plant characterized by a distinctive branch system and cellular anatomy. Arthropitys buritiranensis sp. nov. is proposed to accommodate the new material. The branch architecture is composed of at least three types of branches: (i) principal woody side branches, (ii) up to three secondary woody branches per node, scattered along the stem or the principal side branches, and (iii) 8–11 leafy twigs per whorl, at every third, rarely the second node, without secondary growth. The wood is segmented into fascicular wedges and interfascicular rays, clearly visible only within the inner wood of the stem and woody branches. The tracheid walls of the secondary xylem have exclusively scalariform pits. Ray parenchyma cells have pitted horizontal walls. The new calamitalean was part of the riparian vegetation of tree ferns, calamitaleans and gymnosperms recorded in a distal fluvial plain setting. The wood shows irregular growth interruptions and, therefore, points to a seasonally dry climate that shaped even low latitude paleofloras of tropical Pangaea. • A new calamitalean stem is described from the Parnaíba Basin/Brazil. • Based on the anatomy and branching architecture Arthropitys buritiranenis sp. nov. is introduced. • A revised chart describing anatomically preserved calamitaleans is presented. [ABSTRACT FROM AUTHOR]

Continuing the study of petrified gymnosperm trunks recovered from the Pedra de Fogo Formation, we identify here two new taxa from the Permian deposits of the Parnaíba Basin, northeastern Brazil. One taxon is an endemic form named Ductolobatopitys mussae Conceição, Neregato et Iannuzzi, nov. gen., nov. sp., characterized by solenoid, lobed and non-septate heterocellular pith, cauline bundles with endarch maturation, and secondary xylem with araucarian radial pitting on the tracheid walls. The other form is assigned to the genus Kaokoxylon , which has been recorded from most of Gondwana, including the Parnaíba Basin, but is recorded for the first time from the Pedra de Fogo Formation with the new species Kaokoxylon brasiliensis. It is characterized by solid, non-septate heterocellular pith with sclerenchyma cells, endarch cauline bundles, and uni-to triseriate radial pitting on the walls of the tracheids. The sedimentological interpretations of the outcrops where the fossils were collected indicate that these plants lived on the shores of large continental lakes, with relatively high humidity but possibly periods of drought. These inferences are supported by growth interruptions in the secondary xylem, the presence of calamitalean and tree-fern stems, and microbialites that crop in the same area. These new finds not only increase the known diversity of the flora in the Pedra de Fogo Formation, but also provide more accurate information for understanding the floristic elements that formed the subtropical flora during the Cisuralian in this basin in Western Gondwana. [ABSTRACT FROM AUTHOR]

Tonsteins are layers generated from volcanic ash fall and constitute an important chronostratigraphic marker that allows the correlation between layers in and out of the sedimentary basin, as well as the calibration of biostratigraphic frameworks. In this contribution a new occurrence of tonstein is reported associated with the coal seams in Paraná state, in the Paraná Basin, and it was used as a tie point in local and intra-Gondwanan palynostratigraphy. First, the volcanic origin of the layer was attested by using methods as petrography, SEM and XRD. Then, the layer was dated by U-Pb zircon with LA-ICP-MS method, obtaining an age of 286 ± 3 Ma which corresponds to the Artinskian (middle Cisuralian), thus the layers are correlated with the coal seam from Faxinal coalfield. However, the palynostratigraphic position for the studied interval was at the Protohaploxypinus goraiensis Subzone (lower Vittatina costabilis Zone), due to the presence of Protohaploxypinus goraiensis , Illinites unicus , Vittatina , and Converrucosisporites confluens while palynostratigraphy of Faxinal places it at the Hamiapollenites karooensis Subzone (upper Vittatina costabilis Zone). Therefore, one possible explanation is that the boundary between the subzones of Vittatina costabilis Zone is younger on the studied site than in the rest of the basin. • A new U-Pb LA-ICP-MS dating is provided for western Gondwana and the Paraná Basin. • This is the first register of tonstein further north in the basin. • Radiometric dating demonstrates that the tonstein layer is Artinskian in age. [ABSTRACT FROM AUTHOR]

Anatomically preserved gymnosperm stems are relatively abundant in the Permian outcrops of the Parnaíba Basin, but their anatomy has rarely been studied in detail. Here we describe two new fossil gymnosperm trunks from the Lower Permian (Cisuralian) strata of the Pedra de Fogo Formation in the municipality of Nova Iorque, southern Maranhão State, northeastern Brazil. Two new genera et species are described, Novaiorquepitys maranhensis and Yvyrapitys novaiorquensis. These taxa have a broad, non-septate pith containing sclerenchyma and secretory cells, a parenchyma sheath, and a system of lacunae. Pycnoxylic secondary xylem with growth interruptions and the radial bordered pits on the tracheid walls are araucarian and mixed types. The recognition of two endemic forms indicates both a high degree of endemism for the flora of the Pedra de Fogo Formation and a higher taxonomic diversity of gymnosperm woods than hitherto noted. In addition, the anatomical characters of these taxa, together with sedimentological data and the presence in the same area of plants that live on the banks of water bodies or in wetlands (e.g., tree ferns and tree-calamitaleans), indicate that these woody plants lived near the shores of large lakes. These findings show that studies of Paleozoic woods in this region are potentially valuable. • There were identified two new genera and species based on pith and wood anatomy. • The new taxa are named as Novaiorquepitys maranhensis and Yvyrapitys novaiorquensis. • These woods significantly increase the taxonomic diversity of Permian gymnosperms in the Parnaíba Basin. • It was concluded that tree-dominated communities lived along the lake shores on mild climate conditions. [ABSTRACT FROM AUTHOR]