Tracheid Pit Research Articles

First record of Brachyoxylon wood from Upper Jurassic of Sichuan Basin, Southwest China and its paleoenvironmental significance

Diverse and abundant foliage fossils are well known and well documented from the Upper Triassic to the Lower and Middle Jurassic of Sichuan Basin in Southwest China. Yet, the fossil record of Upper Jurassic plants in this region is sparse. Decades ago, hundreds of fossil wood specimens were unearthed from the Upper Jurassic in the central part of the Sichuan Basin, offering important insights into region’s past terrestrial ecosystems and paleoclimate. Despite their significance, systematic studies of these fossils have been limited. Here, we describe the anatomy of a fossil wood specimen from the Upper Jurassic Penglaizhen Formation in Shehong City, Sichuan Province. The specimen displays key Brachyoxylon features, including mixed radial tracheid pitting in conjunction with araucarioid cross-field pitting. This is the first record of the coniferous wood Brachyoxylon in the central Sichuan Basin. Paleoclimatic evidence from associated leaves, pollen, and sediments, suggests that these trees thrived under generally warm and semi-arid to arid conditions, likely in riparian and lacustrine environments with local water abundance, as indicated by the growth rings with narrow latewood bands.

What do we know about the needle xylem structure of the genus Pinus?

Summary Studies of needle xylem structure (NXS) are of importance in understanding the survival, and functioning of conifers, particularly in response to environmental stressors. Herein, I review the current state-of-the-art about the NXS of genus Pinus, focusing on the xylem, tracheid, and pit structure. Genus Pinus is one of the most important and widely distributed genera of forest trees in the Northern Hemisphere. Pine species are adapted to different soil types and extreme environments imposed by elevation and latitude. They grow successfully in the boreal forest, the Mediterranean Basin, and in mountains. The importance of NXS for long-distance water transport in trees is discussed and the relationships between xylem structure and function are highlighted. Little is known about the NXS of pines, as such information was available only for 12 pine species. Moreover, current knowledge about the NXS of pines is mostly based on Pinus sylvestris L., especially regarding the effect of environmental conditions on NXS. So far, tracheid pit structure has been investigated in only one study. Although NXS is also significantly influenced by tree age, the position of needles within the crown, as well as the location of the cross-section along the longitudinal axis of the needle, a detailed needle sampling design is often missing. Hence, it is suggested to extend future studies to other pine species to explain their resistance to drought and cold. Additionally, increasing the number of studies on adult trees and distinguishing between the different types of environmental stress that a tree can face during its life cycle would be beneficial. I strongly appeal to precise description of needle sampling, which will allow us both intraspecific and interspecific comparisons. Increasing knowledge about the NXS of pines will help to better explain their resistance to environmental stress and predict their tolerance to future climate change.

New record of Cretaceous Protocircoporoxylon wood from the Guyang Basin, northern China and its palaeoclimatic implications

Abundant and diversified Mesozoic fossil wood records have been reported in China. However, fossil woods have never been reported in the Guyang Basin, northern China. Here, a new calcified fossil wood specimen was discovered from the Lower Cretaceous Guyang Formation in the Guyang Basin. The present fossil are characterized by araucarian radial tracheid pitting and circopore cross-field pitting, typical of the genus Protocircoporoxylon. The specimen described here are mostly distinguishable from other fossil species of Protocircoporoxylon by the araucarian radial tracheid pitting and the number of pits per cross-field. Therefore, the present wood fossil is established as a new species, Protocircoporoxylon guyangensis Xu X.H. et Zhao Y.M. sp. nov. Up to now, the fossil detail records of Protocircoporoxylon have predominantly been found in the Triassic and Jurassic periods thus far. However, this discovery in Inner Mongolia, northern China indicates that the genus Protocircoporoxylon still into the Early Cretaceous period. The quantitative growth rings analysis of P. guyangensis sp. nov. indicates that it is an evergreen gymnosperm with a leaf retention time of 5–7 years. The fossil wood living in an environment with complacent water supply and weak seasonal fluctuations.

New record of conifer wood Agathoxylon from the Upper Jurassic in the Sichuan Basin, southern China, and its palaeobiodiversity and palaeoclimatic significance

ABSTRACT Although abundant and diverse foliage fossils are well recorded in the Upper Triassic and Lower–Middle Jurassic of the Sichuan Basin in South China, the Upper Jurassic plant fossils are rarely documented due to extensively developed red beds in this basin. Decades ago, abundant fossil wood specimens were discovered from the Upper Jurassic Penglaizhen Formation in the Sichuan Basin. However, detailed investigations on the systematic palaeobotany of these wood fossils are very limited, which hinders further understanding of the terrestrial ecosystem and biota. Here, we describe anatomically well-preserved fossil wood specimens from the Penglaizhen Formation at Wangjiagou Village of Shehong City in the central Sichuan Province. These wood fossils exhibit Agathoxylon anatomy with usually uniseriate contiguous radial tracheid pitting and araucarioid cross-field pitting, representing a new record of Agathoxylon in the Sichuan Basin, and contribute to further understanding of the vegetation composition of the southern phytoprovince in China during the Late Jurassic. Independent palaeoclimatic evidence from leaf, pollen and sediments indicates that the Agathoxylon trees from Shehong area have grown under generally hot and semi-arid or arid environmental conditions, probably in habitats at the banks of rivers and lakes with locally abundant water supply, as indicated by the indistinct growth rings.

New record of the conifer wood taxon Brachyoxylon from the Middle Jurassic in southwestern China, and a global survey of paleobiogeography of the Mesozoic Brachyoxylon occurrences

Fossil wood is one of the most important proxies for terrestrial vegetation composition and continental paleogeographical reconstruction in Earth's history. The conifer wood Brachyoxylon is commonly found in Mesozoic deposits in Europe, Africa, South America, and Antarctica with more than one hundred known occurrences to date. However, only few occurrences (∼5%) are so far documented in China of East Asia. Here, we describe a fossil wood specimen from the Middle Jurassic Upper Shaximiao Formation at Yongxin of Chongqing City in southeastern Sichuan Basin, China, exhibiting typical Brachyoxylon anatomy with mixed radial tracheid pitting and araucarioid cross-field pitting. According to the characters of radial tracheid pitting, cross-field pitting, and ray height, the wood is recognized as Brachyoxylon trautii (Barale) Philippe 1995. To better understand the paleobiogeography of the Mesozoic Brachyoxylon, a global survey of its occurrences is performed, which shows that Brachyoxylon was globally expanding over time with the widest geographic distribution in the Cretaceous.

A new species of Keteleeria (Pinaceae) from the Lower Cretaceous of Inner Mongolia, Northeast China, and its palaeogeographic and palaeoclimatic implications

Keteleeria Carrière (Pinaceae) is a small genus of evergreen conifer trees, with three to five extant species and six variants distributed across China, Laos, and Vietnam. A new species of conifer fossil wood, Keteleeria huolinhensis sp. nov., is described from the Lower Cretaceous Huolinhe Formation in Inner Mongolia, China. This species is characterized by a heterogeneous pith, endarch primary xylem, the presence of axial resin canals, abietinean radial tracheid pitting, mostly taxodioid and occasionally cupressoid cross-field pitting, nodular horizontal and end walls of ray parenchyma cells, and uniseriate rays of 1–15 (mainly 1–8) cell height. This newly discovered fossil wood represents the earliest record of Keteleeria wood, and sheds light on its evolutionary history and palaeogeographical distribution ranges in the geological past. Cladistic analysis based on 12 morphological characteristics supports the assignment of Protopiceoxylon as the ancestral group of Keteleerioxylon and Keteleeria, reflecting the evolution of radial tracheid pitting from the mixed to abietinean type. Quantitative analysis of the growth rings indicated that K. huolinhensis sp. nov. is an evergreen tree with a Leaf Retention Time (LRT) of 1–3 years. The growth ring patterns in the present fossil wood specimen suggest that the Huolinhe Basin experienced a temperate climate with regular seasonal fluctuations, and relatively sufficient water supply during the Early Cretaceous. Traumatic resin canals, wound scars, presumed fungal remains, and insect tracks in the stem contribute to a further understanding of the complex ecological relationships in the Early Cretaceous Huolinhe flora.

Age of heartwood initiation in trunks of young Pinus sylvestris L. trees in the taiga zone

Summary This work is part of a project investigating the heartwood formation process in Scots pine. Despite the economic and ecological importance of pine heartwood (HW), the process of its formation in many respects remains poorly understood. Scientists believe that HW formation in Scots pine begins at 9–20 years, however, systematic studies of HW initiation age in this species have not previously been conducted. Samples were collected from 105 P. sylvestris trees aged 10 to 25 years, growing in the middle and northern taiga subzones, as well as on the border of the northern taiga subzone with the tundra. Samples were taken at the trunk base according to a single technique and processed using two biochemical (peroxidase activity, pinosylvin presence) and two anatomical markers (presence of extractives on the tracheid pit membranes, nuclei disappearance) characterizing different events during HW formation. Biochemical markers showed an overestimation in the number of HW annual rings compared with HW determination based on anatomical criteria by 1–3 years, on average. Attempts to detect peroxidase activity showed a negative result in the inner sapwood annual ring, while detectable pinosylvin accumulation occurred in the transition zone (TZ). We have detected for the first time true HW (without living cells) in Scots pine samples with a cambial age (CA) of 15–17 years. The number of growth rings in TZ and HW in young trees depended on growth conditions. These results are important for understanding the mechanisms of HW formation and developing realistic models of this process, including changing climate conditions.

A quantitative analysis of leaf life span reveals the Mesozoic significant gymnosperm Xenoxylon as evergreen: First evidence from the Early Cretaceous Jehol Biota in northeastern China

The Early Cretaceous Jehol Biota in western Liaoning Province of China and adjacent regions, is one of the most spectacular Mesozoic terrestrial lagerstätten in East Asia. Diversified fossil wood has been reported for the last two decades for the Jehol Biota. However, little is known about the fossil wood from the Lower Cretaceous Jiufotang Formation in the Kazuo area of western Liaoning. Here, we report new fossil wood material from the Lower Cretaceous Jiufotang Formation in Kazuo County of western Liaoning Province, northeastern China with well-preserved xenoxylean radial tracheid pitting and window-like cross-field pitting. Due to a novel combination of radial tracheid pitting, cross-field pitting and ray height, a new species, Xenoxylon kazuoense Xie, Wang, Tian et D.Uhl sp. nov., is recognized here belonging to the gymnosperm. Based on the well-preserved tree growth rings, we first perform a quantitative analysis of leaf life span for the Mesozoic common gymnosperm Xenoxylon. The result shows the tree X. kazuoense sp. nov. was evergreen with a leaf retention time (LRT) of 3–15 years. The discovery of this new species leads to a further understanding of the biodiversity of fossil wood in the Early Cretaceous Jehol Biota and the leaf phenology of trees growing in this area during the Early Cretaceous.

A new extinct conifer Brachyoxylon from the Middle Jurassic in southern China: Wood anatomy, leaf phenology and paleoclimate

The Jurassic System in the Sichuan Basin of eastern Asia is represented by the extensive development of massive thick red beds, mainly composed of purplish-red sandstones and mudstones. Abundant invertebrate and vertebrate fossils have been recovered from these Jurassic red beds. However, fossil woods are much less documented. Here, we describe fossil woods from the Middle Jurassic Shaximiao Formation at Qijiang of Chongqing City in southeastern Sichuan Basin, China, obtaining typical Brachyoxylon anatomy with mixed radial tracheid pitting and araucarioid cross-field pitting. Owing to a novel combination of radial tracheid pitting, cross-field pitting and ray height, a new species, Brachyoxylon qijiangense Xie, Wang et Tian sp. nov. is recognized here. Based on the tree mean sensitivity and leaf retention time analysis, along with the comparison with other invertebrate and leaf fossils in the Shaximiao Formation, the new fossil woods bearing true growth rings with abundant, well-formed earlywood and extremely narrow latewood indicates that B. qijiangense sp. nov. was an evergreen tree growing in a warm and humid climate with mild seasonality during the Middle Jurassic in Qijiang, probably in a flooding-disturbed, streamside condition.

Spatial organization and connectivity of wood rays in Pinus massoniana xylem based on high-resolution μCT-assisted network analysis.

Spatial organization and connectivity of wood rays in Pinus massoniana was comprehensively viewed and regarded as anatomical adaptions to ensure the properties of rays in xylem. Spatial organization and connectivity of wood rays are essential for understanding the wood hierarchical architecture, but the spatial information is ambiguous due to small cell size. Herein, 3D visualization of rays in Pinus massoniana was performed using high-resolution μCT. We found brick-shaped rays were 6.5% in volume fractions, nearly twice the area fractions estimated by 2D levels. Uniseriate rays became taller and wider during the transition from earlywood to latewood, which was mainly contributed from the height increment of ray tracheids and widened ray parenchyma cells. Furthermore, both volume and surface area of ray parenchyma cells were larger than ray tracheids, so ray parenchyma took a higher proportion in rays. Moreover, three different types of pits for connectivity were segmented and revealed. Pits in both axial tracheids and ray tracheids were bordered, but the pit volume and pit aperture of earlywood axial tracheids were almost tenfold and over fourfold larger than ray tracheids. Contrarily, cross-field pits between ray parenchyma and axial tracheids were window-like with the principal axis of 31.0μm, but its pit volume was approximately one-third of axial tracheids. Additionally, spatial organization of rays and axial resin canal was analyzed by a curved surface reformation tool, providing the first evidence of rays close to epithelial cells inward through the resin canal. Epithelial cells had various morphologies and large variations in cell size. Our results give new insights into the organization of radial system of xylem, especially the connectivity of rays with adjacent cells.

A new conifer stem, Ductoagathoxylon tsaaganensis, from the Upper Permian of the South Gobi Basin, Mongolia and its palaeoclimatic and palaeoecological implications

Permineralised stems of Ductoagathoxylon tsaaganensis Cai, Zhang et Feng sp. nov. are described from the Upper Permian strata of the Tsaagan Tolgoy section, South Gobi Basin, Mongolia. The stems were preserved with pith and primary and secondary xylems. The pith is solid, heterocellular, and characterised by regularly arranged clusters of secretory cells at the periphery. The primary xylem is the endarch and mesarch. The tracheid walls exhibited annular, helical, and scalariform thickening from the protoxylem to metaxylem. The secondary xylem is of the Agathoxylon-type and is composed of tracheids and parenchymatous rays. The growth rings of the stems were distinct, with broad earlywood and narrow latewood. Radial tracheid pits in the secondary xylem are contiguous and alternately arranged, uni- or biseriate in the latewood, and bi- to tetraseriate in the earlywood. Rays are uniseriate and 1–7 (mostly 2–4) cells high. Each cross-field possessed 1–19 (mostly 3–9) cupressoid pits. Quantitative analysis of the growth rings indicated that the plant was likely a deciduous conifer that lived in a seasonal, temperate, and wet climate. However, a growth interruption with inflated cells was present in the secondary xylem, indicating that the tree had survived climatic damage, probably an early spring cooling event. Fungal remains, including hyphae and spores, and evident white-rot patterns in the stems revealed a common occurrence of fungal infections in the ecosystem. Our study sheds new light on the plant diversity and climatic and ecological features of the Angara flora during the Late Permian in the South Gobi Basin.

A more southerly occurrence of Xenoxylon in North America: X. utahense Xie et Gee sp. nov. from the Upper Jurassic Morrison Formation in Utah, USA, and its paleobiogeographic and paleoclimatic significance

Although Xenoxylon is a global genus of Mesozoic wood in the Northern Hemisphere, it is striking that the valid records in North America occur only in the northernmost parts of the continent. Decades ago, two species of Xenoxylon were described from the Upper Jurassic Morrison Formation in Utah, USA. However, a recent review of all North American reports of Xenoxylon excluded both species from the genus based on their anatomy, rendering all records of this genus south of Montana invalid in 2019. Here we describe a fossil log from the Morrison Formation near Vernal, northeastern Utah, USA, with true Xenoxylon anatomy with locally xenoxylean radial tracheid pitting and fenestriform crossfield pitting. Due to a novel combination of radial tracheid pitting, crossfield pitting and ray height, a new species, Xenoxylon utahense Xie et Gee sp. nov., is recognized here. Located at the southernmost occurrence of Xenoxylon in North America during the Mesozoic, this new species confirms that Xenoxylon trees were not only restricted to a circumpolar zone, but also grew in more southerly areas. In comparison with other fossil plants in the Morrison Formation of Utah, along with growth ring characteristics and climatic preferences of living conifers, the new fossil log with true growth rings with abundant, well-formed earlywood and extremely little latewood argues for a warm and humid climate with very mild seasonality for the Late Jurassic in this region, which is inconsistent with previous interpretations of Xenoxylon as a reliable indicator of cool climates.

Morphological, microscopic, and physicochemical studies of Diospyros montana.

Adulteration is the root cause of producing not only a chemically and pharmacologically inferior but also in some instances hazardous or poisonous drug. Despite availability of several techniques, microscopy and physicochemical analyses are the most practical approaches for crude drug authentication. Hence, the present study aimed to evaluate morphological, microscopic, and physicochemical properties of root, bark, leaf, and fruit of Diospyros montana Morphological properties were determined by sensory organs, whereas microscopic features of cross-sections and powders were determined by light and scanning electron microscopy. The proximate and fluorescence analyses were performed using the standard guidelines. The physical examination of fresh, shade-dried, and powdered material showed no significant change in color. The identifying cellular structures included cuboidal cork, pitted tracheids, scalariform, reticulate and spiral xylary vessels, and rosettes, raphide, and cuboidal calcium oxalate crystals. The stomatal number, stomatal index, vein-islet and vein-termination number, and palisade ratio in the leaf were found to be 293.91 ± 32.68 mm-2 , 64.18 ± 3.42%, 22.00 ± 3.81 mm-2 and 38.40 ± 5.81 mm-2 , and 3.85 ± 0.60, respectively. Total ash, acid insoluble ash, water soluble ash and sulfated ash of leaf (9.00 ± 0.50%, 1.67 ± 0.23%, 2.00 ± 0.22% and 14.50 ± 0.99%, respectively), foaming index of bark and root (111.11 ± 2.11), and swelling index of fruit (19.00 ± 3.45) were higher than the other parts. The powder of different parts showed characteristic colors in the daylight and UV light upon treatment with various regents. The plant was found to be rich in saponins, fibers, and flavonoids. The results of the present study may serve as identifiers of different parts of Diospyros montana.

Dispersed plant mesofossils from the Permian of Wuda, Inner Mongolia, Taiyuan Formation, China

A coal sample from the Lower Permian Taiyuan Formation (Wuda locality, Inner Mongolia, China) was macerated. It yielded two cuticle fragments and many fragments of conducting tissue. One cuticle fragment shows strongly corroded polygonal cells belonging either to a pteridosperm or a cycad. The second fragment is an abaxial cordaitalean cuticle with papillate tetragonal cells and can be compared to Cordaites neimengensis LIU et al. 1998. The conducting tissue are represented by biseriate to quadriseriate tracheid pitting that is typical for cordaitaleans.

Development and Standardization of Narayana Churna—A Polyherbal Ayurvedic Formulation

Aim: The present study aims to develop pharmacognostical standards, standard operating procedure (SOP), and analytical profiling including physicochemical analysis of Narayana Churna, a polyherbal Ayurvedic formulation. Materials and methods: The pharmacognostical (macroscopy, microscopy and powder drug analysis), thin layer chromatography (TLC), and quantitative physicochemical analysis including loss on drying, alcohol and water-soluble extractive values, total and acid-insoluble ash, and pH value were performed as per the standard procedures described in the Ayurvedic Pharmacopoeia of India (API). The microbial limit, aflatoxins, heavy metals and pesticide residues were also analyzed. Results and discussion: Narayana Churna is of grayish-brown color with a slightly pungent taste. The powder microscopy revealed the presence of pentagonal/hexagonal/polygonal cork cells, polygonal pale green endosperm, oval/polygonal/irregular shaped stone cells, elongated and flat-shaped bordered pitted vessels, pitted tracheids, annular vessels, unicellular covering trichomes, prismatic crystals of calcium oxalate, starch grains and oil globules. The TLC fingerprint was developed using toluene:ethyl acetate:formic acid (6:4:1) as the solvent system. The standardized limits of the physicochemical parameters, microbial count, aflatoxins, heavy metals and pesticide residues were also laid down. Conclusion: This is the first ever attempt made in order to develop the SOP and standardized parameters of Narayana Churna. Thus, the present study would be useful as the standardized reference protocol for the identification and standardization of this formulation.

Systematics and taphonomy of fossil woods from a new locality in the Upper Triassic Carrizal Formation of the El Gigantillo area (Marayes-El Carrizal Basin), San Juan, Argentina

We present a new locality with fossil woods in the southern outcrops of the Rickard Member, Carrizal Formation (Upper Triassic) of the El Gigantillo area in San Juan Province, Argentina. We analyzed the anatomical characters, systematic affinity and taphonomic conditions of permineralized trunks. A total of 58 trunks were found, although only two samples of the silicified trunks preserved anatomy details, and were characterized by a pycnoxylic homoxylic secondary wood with distinct growth rings, latewood 2–4 cells wide, tracheid pitting in radial walls of mixed type, cross-fields of cupressoid type with 1–4 oculipores, and homocellular and mainly uniseriate rays 1–19 cells high with smooth ray cell walls. The taphocenosis of the logs were preserved by carbonatic and siliceous permineralization, which are located in floodplains and channel deposits and constitute an allochthonous and parautochthonous taphocoenosis. The silicified wood presented high organic perturbation probably related to fungal activity, as well as several cylindrical and tubular galleries and pellets, which probably represented the activity of arthropods. The studied specimens were assigned to the new species Protocupressinoxylon carrizalense sp. nov. and constitute the first cite of the genus Protocupressinoxylon from the Triassic of Argentina. They thus represent the arboreal paleocommunities that grew in the top of the bars within the channels and riparian areas.

Fossil Conifer Woods from Cerro Piche Graben (Triassic–Jurassic?), North Patagonian Massif, Río Negro Province, Argentina

Fossil conifer woods are described for the first time in sedimentary rocks from Cerro Piche Graben, North Patagonian Massif, Argentina. The permineralized axes are chacaracterized by a pith constituted by parenchyma cells and a few sclerenchyma cells; secondary xylem homoxylic and pycnoxylic, without distinct growth rings; tracheid pits uniseriate and mainly spaced; cross fields cupressoid, with 3 to 8 pits; and rays homocellular, uniseriate and low. Based on these characteristics, the woods are assigned to Cupressinoxylon. Until now, the only fossil plants known from Cerro Piche were two specimens of Pleuromeia sp., which are reinterpreted also as conifer fossil remains.

Cenozoic conifer wood from the Gore Lignite Measures, Southland, New Zealand

ABSTRACTWell preserved fossil wood in the form of tree stumps, logs, branches, roots and occasionally bark is common throughout the Gore Lignite Measures, southern New Zealand. The main objective of the present study is to identify the range of forest trees present using anatomical features such as: distinct growth rings; presence or absence of axial parenchyma; uniseriate to triseriate, opposite to alternate, separate or contiguous tracheid pitting; and taxodioid, cupressoid and araucarioid cross-field pitting. Specimens of silicified and lignified wood are described and illustrated from four localities within the Late Oligocene–Early Miocene Gore Lignite Measures, Southland: Newvale Coal Mine; Mataura Coal Mine; Cosy Dell Coal Pit; and Bennett’s Pit. The fossil wood specimens include examples of Araucariaceae, Cupressaceae and Podocarpaceae. Three specimens from Newvale Mine resemble Araucariaceae, while one is assigned to Cupressaceae. Cosy Dell Coal Pit preserved branches of Podocarpaceae. Large stumps and branches preserved at the Mataura Coal Mine are identified as Cupressaceae and Podocarpaceae. Wood recovered from Bennett’s Pit resembles either Cupressaceae or Podocarpaceae. Araucariaceae, in the form of Agathis Salisb. trees are today restricted to the northern North Island. Cupressaceae and Podocarpaceae are still extant in modern forests throughout New Zealand. So far, no angiosperm wood has been recognised from the lignite deposits. The forests in which these trees lived were in or near oligotrophic swamps on a deltaic plain. Identification of samples of fossil wood provides new data that can be used to reconstruct the forest vegetation of the Gore Lignite Measures.

Yangquanoxylon miscellum gen. nov. et sp. nov., a gymnospermous wood from the Upper Pennsylvanian–lower Permian Taiyuan Formation of Yangquan City, Shanxi Province, with reference to the palaeoclimate in North China

A silicified gymnospermous wood, Yangquanoxylon miscellum gen. nov. et sp. nov., is described from the Upper Pennsylvanian-lower Permian Taiyuan Formation, Yangquan City, Shanxi Province, North China. The pycnoxylic wood is composed of thick-walled tracheids and thin-walled rays. It is characterized by mixed radial tracheid pits, uniseriate and homogeneous rays, occurrence of scalariform radial pitting, and various types of cross-field pitting. There are four types of cross-field pitting in Y. miscellum gen. nov. et sp. nov., including simple, taxodioid, phyllocladoid, and araucarioid. The absence of growth rings within fossil woods described here and reported previously from North China suggests a humid climate with minimal precipitation variations during the Late Pennsylvanian-early Permian.

New petrified calamitaleans from the Permian of the Parnaíba Basin, central-north Brazil, part II, and phytogeographic implications for late Paleozoic floras

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.