- Earth Sciences,
University of Birmingham,
Edgbaston, Birmingham,
B15 2TT, UK. - +44 (0)121 4146151
- Jason's research interests focus on palaeobotany and evolutionary plant biology and related disciplines including phy... moreJason's research interests focus on palaeobotany and evolutionary plant biology and related disciplines including phylogeny, evolution and environmental change. You can find a full list of his publicatoins on researcherid.com as Researcher F-5830-2012 (http://www.researcherid.com/rid/F-5830-2012).
If you want a copy of one of my papers, e-mail me for a copy.edit
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Significance The Carnian Stage of the Triassic Period marks one of the most significant intervals of the past 250 My. Within the space of ∼2 My, the world’s biota underwent major changes with dinosaurs becoming the notable incumbents.... more
Significance The Carnian Stage of the Triassic Period marks one of the most significant intervals of the past 250 My. Within the space of ∼2 My, the world’s biota underwent major changes with dinosaurs becoming the notable incumbents. These events coincide with a remarkable interval of intense rainfall known as the Carnian Pluvial Episode (CPE). Here, we show, in a detailed record from a lake in North China, that the CPE can actually be resolved into four distinct events, each one driven by a discrete pulse of intense volcanism associated with enormous releases of carbon dioxide into the atmosphere. These triggered a major intensification of the hydrological cycle and led to lake eutrophication.
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Research Interests: Botany, Evolutionary Biology, Paleobotany, Plant Biology, Biology, and 10 moreChina, Pollen, Permian, Plant, Plant sciences, Genus, Cardiocarpus, Cordaites, Phyllotaxis, and ovule
Research Interests: Botany, Evolutionary Biology, Paleobotany, Plant Biology, Biology, and 10 moreChina, Pollen, Permian, Plant, Plant sciences, Genus, Cardiocarpus, Cordaites, Phyllotaxis, and ovule
Research Interests: Botany, Evolutionary Biology, Paleobotany, Plant Biology, Biology, and 10 moreChina, Pollen, Permian, Plant, Plant sciences, Genus, Cardiocarpus, Cordaites, Phyllotaxis, and ovule
Description of studied sections, biostratigraphy of Lopingian–Middle Triassic in North China, the results of statistical analysis, R scripts, and Supplementary Data Files: (1) Geological distributions of fossil plants, sporomorphs and... more
Description of studied sections, biostratigraphy of Lopingian–Middle Triassic in North China, the results of statistical analysis, R scripts, and Supplementary Data Files: (1) Geological distributions of fossil plants, sporomorphs and fossil woods; (2) Detailed descriptions of floras in North China; (3) Plant genera distributions and number of genera in each stratigraphic unit; (4) Plant zones, subzones and assemblages from Cisuralian to Anisian in North China; (5) Invertebrate genera distributions and number of genera in each stratigraphic unit; (6) Insect genera distributions and number of genera in each stratigraphic unit; (7) Vertebrate genera distributions and number of genera in each stratigraphic unit; (8) Global floral changes from Lopingian to Middle Triassic; (9) Hygrophyte, mesophytes and xerophyte element distributions; (10) Hygrophte and Xerophyte ratios.
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The End-Triassic Mass Extinction (ETME) saw the catastrophic loss of ca. 50% of marine genera temporally associated with emplacement of the Central Atlantic Magmatic Province (CAMP). However, the effects of the ETME on land is a... more
The End-Triassic Mass Extinction (ETME) saw the catastrophic loss of ca. 50% of marine genera temporally associated with emplacement of the Central Atlantic Magmatic Province (CAMP). However, the effects of the ETME on land is a controversial topic. Evaluation of the disparate cause(s) and effects of the extinction requires additional, detailed terrestrial records of these events. Here, we present a multidisciplinary record of volcanism and environmental change from an expanded Triassic-Jurassic (T-J) transition preserved in lacustrine sediments from the Jiyuan Basin, North China. High-resolution chemostratigraphy, palynological, kerogen, and sedimentological data reveal that terrestrial conditions responded to and were defined by large-scale volcanism. The record of sedimentary mercury reveals two discrete CAMP eruptive phases during the T-J transition. Each of these can be correlated with large, negative C isotope excursions (CIE-I of −4.7‰; CIE-II of −2.9‰), significantly reduced...
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Three-dimensional reconstruction of the structure and organization of <em>Dorsalistachya quadrisegmentorum</em> rendered with Blender. Available in .AVI (Audio Video Interleaved) and .MOV (Apple Quicktime) format.
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ABSTRACT Hydrasperman pteridosperms (seed ferns) were widespread and diverse in Carboniferous equatorial wetlands of Euramerica, and although present in Permian equatorial wetlands in Cathaysia, little is known about their ovules... more
ABSTRACT Hydrasperman pteridosperms (seed ferns) were widespread and diverse in Carboniferous equatorial wetlands of Euramerica, and although present in Permian equatorial wetlands in Cathaysia, little is known about their ovules (unfertilised seeds) from this phytogeographical realm. Hydrasperman ovules are recognisable from their distinctive pollen chamber organisation, but those previously noted from the Permian floras of Cathaysia are imperfectly characterised and require further study to confirm their affinity and identity. Here we document the hydrasperman ovule Conostoma cf. kestospermum from coal-balls in the early Permian aged Taiyuan Formation of North China for which preliminary findings were previously published in a Chinese language book on the coal-ball floras of China. We provide additional information on the organisation and structure of the ovules and for the first time consider their palaeoecological and palaeogeographical significance. We conclude that significant taxonomic filtering occurred in the migration of wetland plant species between Euramerica and Cathaysia in the late Pennsylvanian, with the majority of hydrasperman pteridosperms going extinct in Euramerica at the end of the Carboniferous as a result of habitat loss and climate change. The few hydrasperman genera and species that persisted into the Cathaysian flora were relicts and a minor component of Permian equatorial wetland floras.
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Significance There were two heterosporous lignophyte lineages of which only one, the seed plants, survived the Permian–Triassic mass extinction. Based on exceptionally complete fossil trees from a 300-My-old volcanic ash, the enigmatic... more
Significance There were two heterosporous lignophyte lineages of which only one, the seed plants, survived the Permian–Triassic mass extinction. Based on exceptionally complete fossil trees from a 300-My-old volcanic ash, the enigmatic Noeggerathiales are now recognized as belonging to the other lineage. They diversified alongside the primary seed plant radiation and constitute seed plants’ closest relatives. Noeggerathiales are reconstructed as members of a plexus of free-sporing woody plants called progymnosperms, extending their age range by 60 My. Following the origin of seed plants, progymnosperms were previously thought to have become gradually less abundant before dying out in Carboniferous. We show they diversified and evolved complex morphologies including cone-like structures from modified leaves before going extinct at the Permian–Triassic extinction.
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Noeggerathiales are an extinct group of heterosporous shrubs and trees that were widespread and diverse during the Pennsylvanian-Permian Epochs (323-252 Ma) but are of controversial taxonomic affinity. Groups proposed as close relatives... more
Noeggerathiales are an extinct group of heterosporous shrubs and trees that were widespread and diverse during the Pennsylvanian-Permian Epochs (323-252 Ma) but are of controversial taxonomic affinity. Groups proposed as close relatives include leptosporangiate ferns, sphenopsids, progymnosperms, or the extant eusporangiate fern Tmesipteris. Previously identified noeggerathialeans lacked anatomical preservation, limiting taxonomic comparisons to their external morphology and spore structure. We here document from the upper Permian of China the first anatomically preserved noeggerathialeans, which enhance the perceived distinctiveness of the group and better indicate its systematic affinity. We describe in detail the newly discovered, anatomically preserved heterosporous strobilus Dorsalistachya quadrisegmentorum, gen. et sp. nov., and redescribe its suspected foliar correlate, the pinnate leaf Plagiozamites oblongifolius. Plagiozamites possesses an omega (Ω)-shaped vascular trace an...
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Research Interests: Botany, Evolutionary Biology, Geography, Biology, Ecology, and 15 moreDiatoms, Morphogenesis, Medicine, Palaeobotany, Fossils, North Carolina, Middle Jurassic, Biological evolution, British Columbia, Fossil conifers, Cupressaceae, Evolution of Conifers, MADS Box Genes, Palaeoclimates, and coniferales
ABSTRACT A new species of permineralised marattialean fern trunk is described from Lopingian (late Permian) aged volcaniclastic tuffs from Panxian County, western Guizhou Province, China and named Psaronius xuii sp. nov. The stem has... more
ABSTRACT A new species of permineralised marattialean fern trunk is described from Lopingian (late Permian) aged volcaniclastic tuffs from Panxian County, western Guizhou Province, China and named Psaronius xuii sp. nov. The stem has vascular bundles that are encircled by a bi-layered sheath and has a ground tissue consisting of thicker-walled and thinner-walled parenchymatous cells and dispersed nests of sclerenchymatous cells. Two sclerenchymatous strands occur between neighboring stelar cycles, with this species lacking a peripheral sclerenchyma sheath and possessing a &amp;quot;chrysanthemum&amp;quot;-shaped sclerenchyma strands in the adaxial bay of the peripheral vascular bundles. Although distinct from other species, comparisons demonstrate a consistent organisation amongst contemporaneous species from South Cathaysia that have sclerenchymatous strands in the adaxial bay of the peripheral vascular bundles, vascular bundles and leaf traces surrounded by a vascular bundle sheath, and the middle part of the leaf trace is depressed inward after departing from the peripheral vascular bundle. These features are used to define the Panxianensis Group named after the most comprehensively known species, P. panxianensis. Species within the Panxianensis Group differ from other species from the Carboniferous and Permian floras of Euramerica, Gondwana and North Cathaysia that we place in the Blicklei Group that lack sclerenchymatous strands in the adaxial bay of the peripheral vascular bundles, lack vascular bundle sheaths, and the middle part of the leaf trace is arched outwards when they depart from the peripheral vascular bundles. Members of the Panxianensis Group appear to represent a relatively derived group that appears to be endemic to South Cathaysia, with these presumably evolving from members of the Blicklei Group in the Cisuralian or Guadalupian.
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ABSTRACT A new species of Medullosan ovule from the Mazon Creek Carboniferous lagerstätte is documented using a novel combination of non-invasive X-Ray Micro-Tomography (XMT) and orientated precision sectioning based on the XMT results.... more
ABSTRACT A new species of Medullosan ovule from the Mazon Creek Carboniferous lagerstätte is documented using a novel combination of non-invasive X-Ray Micro-Tomography (XMT) and orientated precision sectioning based on the XMT results. 3-D reconstruction of the ovule has correlated geometries of different layers with tissue characteristics gathered from wafered sections, with the methodological combination presenting a virtual reconstruction of the specimen and also enabling positioning of serial sections of the holotype in pre-determined positions. Stephanospermum braidwoodensis sp. nov. has four longitudinally orientated sarcotestal wings, two to each side of the major plane that demonstrate 180° rotational (bilateral) symmetry, while the sclerotesta has three prominent longitudinal commissural ribs and the pollen chamber has three small ribs and triangular nucellar beak, both demonstrating radial (threefold) symmetry. This demonstration of both radial and bilateral symmetries in different tissues emphasises the complexities of inferring systematic affinities of fossil seeds from symmetry alone. We consider S. braidwoodensis to be closely related to the co-occurring S. konopeonus Drinnan et al., and postulate that it was born on a fertile truss similar to that of the latter species. Finally implications of our findings for the utility of these methods in identifying additional species from the Mazon Creek biota are discussed, and the advantages and disadvantages of different methods of nodule preparation are considered. We conclude that additional species are likely to be recognised from the Mazon Creek flora by application of the same methodologies used in this investigation.
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ABSTRACT Reinvestigation of the anatomically preserved stem Palaeosmunda plenasioides from the Lopingian (Late Permian) of China has led to the establishment of Zhongmingella gen. nov. within the extinct family Guaireaceae (Osmundales).... more
ABSTRACT Reinvestigation of the anatomically preserved stem Palaeosmunda plenasioides from the Lopingian (Late Permian) of China has led to the establishment of Zhongmingella gen. nov. within the extinct family Guaireaceae (Osmundales). Zhongmingella has a rhizomatous stem with heterogeneous pith and cortex comprising parenchyma and uniformly distributed secretory cells, and is dictyostelic. In order to evaluate the systematic and phylogenetic position of Zhongmingella within Guaireaceae, and Guaireaceae within Osmundales, we conducted a preliminary cladistic analysis of a broad range of Osmundales and related taxa based on 18 extinct and six extant genera and subgenera. Results do not support the traditionally defined family Thamnopteroideae (Bathypteris, Chasmatopteris, Iegosigopteris, Thamnopteris, Zalesskya) and demonstrate that Thamnopteroideae is not a subfamily of Osmundaceae as previously thought. Guaireaceae is monophyletic but in addition to its traditionally defined members (Guairea, Lunea, Donwellicaulis, Itopsidema, Shuichengella, Zhongmingella) includes the stratigraphically younger genus Osmundacaulis previously placed in Osmundaceae. Guaireaceae is sister to Osmundaceae, Millerocaulis, Ashicaulis, Palaeosmunda and Aurealcaulis in the strict consensus, but in the majority-rule consensus Palaeosmunda, Aurealcaulis, Ashicaulis and Millerocaulis form the Osmundaceae stem group, with (Aurealcaulis, (Ashicaulis + Palaeosmunda)) sister to the extant genera. Stratigraphical analysis of the selected most parsimonious tree demonstrates that Osmundales underwent primary radiation during the Pennsylvanian and Permian, terminating abruptly around the time of the end-Permian mass extinction. Radiation within Osmundaceae occurred in the Triassic–Cretaceous and stratigraphically overlaps staggered extinctions in Guaireaceae and Osmundaceae from the Late Jurassic to mid-Cretaceous alongside the earliest angiosperm radiation. Our results identify the Osmundaceae stem and sister groups for the first time, and represent an important step in unravelling the evolutionary history of Osmundales. However, reconstructed whole-plant species are imperative to improve understanding of the relationships within the clade in deep time.
Research Interests: Evolutionary Biology, Geology, Paleontology, Biology, Ecology, and 4 moreEvolution, Palaeozoic, Permian, and Monophyly
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Summary The strong positive relationship evident between cell and genome size in both animals and plants forms the basis of using the size of stomatal guard cells as a proxy to track changes in plant genome size through geological time.... more
Summary The strong positive relationship evident between cell and genome size in both animals and plants forms the basis of using the size of stomatal guard cells as a proxy to track changes in plant genome size through geological time. We report for the first time a taxonomic fine‐scale investigation into changes in stomatal guard‐cell length and use these data to infer changes in genome size through the evolutionary history of land plants. Our data suggest that many of the earliest land plants had exceptionally large genome sizes and that a predicted overall trend of increasing genome size within individual lineages through geological time is not supported. However, maximum genome size steadily increases from the Mississippian (c. 360 million yr ago (Ma)) to the present. We hypothesise that the functional relationship between stomatal size, genome size and atmospheric CO2 may contribute to the dichotomy reported between preferential extinction of neopolyploids and the prevalence o...
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Research Interests: Paleontology, Biology, Palaeoecology, Diatoms, Medicine, and 14 morePalaeontology, Synchrotron Radiation, Palaeobotany, United Kingdom, Gondwana, Three dimensional modeling and simulation, Tithonian, Gymnosperm, Silicification, Late Jurrasic, Laurasia, Palaeoclimates, diamond light source, and ovule
Three-dimensional reconstruction model of <em>Dorsalistachya quadrisegmentorum</em> in SPIERSView and VAXML format. Notes: SPIERSView file (.SPV) models can conveniently be viewed using the SPIERSView software, freely... more
Three-dimensional reconstruction model of <em>Dorsalistachya quadrisegmentorum</em> in SPIERSView and VAXML format. Notes: SPIERSView file (.SPV) models can conveniently be viewed using the SPIERSView software, freely available in both Windows and Mac versions from http://www.spiers‐software.org. However, note that low-performance computers may not possess a sufficiently powerful graphics card to render and rotate the model. VAXML file format models are saved as a ZIP-compressed VAXML datasets. VAXML uses one or more .STL files to define the geometry of objects that comprise the dataset, together with one .VAXML file that provides metadata on the dataset as a whole, and specifies how the .STL files should be put together. We recommend using the free SPIERS software to view this model format (http://spiers-software.org/). However, .STL files can be opened independently in several freely available software programs (e.g. MeshLab, Blender). Additional information on the VAX...
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Most knowledge concerning Mesozoic Era floras has come from compression fossils. This has been augmented in the last 20 years by rarer permineralized material showing cellular preservation. Here, we describe a new genus of anatomically... more
Most knowledge concerning Mesozoic Era floras has come from compression fossils. This has been augmented in the last 20 years by rarer permineralized material showing cellular preservation. Here, we describe a new genus of anatomically preserved gymnosperm seed from the Callovian–Oxfordian (Jurassic) Oxford Clay Formation (UK), using a combination of traditional sectioning and synchrotron radiation X-ray micro-tomography (SRXMT). Oxfordiana motturii gen. et sp. nov. is large and bilaterally symmetrical. It has prominent external ribs, and has a three-layered integument comprising: a narrow outer layer of thick walled cells; a thick middle parenchymatous layer; and innermost a thin fleshy layer. The integument has a longitudinal interior groove and micropyle, enveloping a nucellus with a small pollen chamber. The large size, bilateral symmetry and integumentary groove demonstrate an affinity for the new species within the cycads. Moreover, the internal groove in extant taxa is an aut...
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PREMISE OF THE STUDY: Noeggerathiales are an extinct group of heterosporous shrubs and trees that were widespread and diverse during the Pennsylvanian– Permian Epochs (323–252 Ma) but are of controversial taxonomic affi nity. Groups... more
PREMISE OF THE STUDY: Noeggerathiales are an extinct group of heterosporous shrubs and trees that were widespread and diverse during the Pennsylvanian– Permian Epochs (323–252 Ma) but are of controversial taxonomic affi nity. Groups proposed as close relatives include leptosporangiate ferns, sphenopsids, progymnosperms, or the extant eusporangiate fern Tmesipteris. Previously identifi ed noeggerathialeans lacked anatomical preservation, limiting taxo-nomic comparisons to their external morphology and spore structure. We here document from the upper Permian of China the fi rst anatomically preserved noeggerathialeans, which enhance the perceived distinctiveness of the group and better indicate its systematic affi nity. METHODS: We describe in detail the newly discovered, anatomically preserved heterosporous strobilus Dorsalistachya quadrisegmentorum , gen. et sp. nov., and redescribe its suspected foliar correlate, the pinnate leaf Plagiozamites oblongifolius. KEY RESULTS: Plagiozami...
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Background and Aims.The largely Mississippian strata of the Kilpatrick Hills, located at the western end of the Scottish Midland Valley, enclose several macrofossil floras that together containca21 organ-species of permineralised plants... more
Background and Aims.The largely Mississippian strata of the Kilpatrick Hills, located at the western end of the Scottish Midland Valley, enclose several macrofossil floras that together containca21 organ-species of permineralised plants andca44 organ-species of compressed plants, here estimated to represent 25 whole-plant species (Glenarbuck = nine, Loch Humphrey Burn Lower = 11, Upper = seven). The most significant locality is the internationally important volcanigenic sequence that is reputedly intercalated within the Clyde Plateau Lava Formation at Loch Humphrey Burn, whereca30 m of reworked tuffs and other clastic sediments enclose one of the world’s most important terrestrial lagerstätten of this period. We here explore the palaeoecology and palaeoenvironments of the locality, and elucidate its controversial age.Methods.Repeated re-excavation of key exposures allowed recognition of five main depositional units, differing in thickness from 4 m to 12 m. It also permitted detailed...
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Información del artículo Erratum to ¿Foliar physiognomy in Cathaysian gigantopterids and the potential to track Palaeozoic climates using an extinct plant group¿ [Palaeogeogr. Palaeoclimato 1. Palaeoecol. 205/1-2 (2004) 69-110].
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GFF volume 133 (2011), pp. 57–75. Lundadagarna i Historisk Geologi och Paleonotologi XII 17–18th of March, 2011 Organised by KRISTINA MEHLQVIST and ELISABETH EINARSSON Meeting proceedings Downloaded by [University of Stockholm] at 10: 35... more
GFF volume 133 (2011), pp. 57–75. Lundadagarna i Historisk Geologi och Paleonotologi XII 17–18th of March, 2011 Organised by KRISTINA MEHLQVIST and ELISABETH EINARSSON Meeting proceedings Downloaded by [University of Stockholm] at 10: 35 14 September 2011 Lundadagarna i Historisk Geologi och Paleontologi is a conference held every second year at the Department of Earth and Ecosystem Sciences, Division of Geology, Lund University. Since the start in 1989, Lundadagarna has been an important opportunity ...
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Evidence for invertebrate feeding on glossopterid gymnosperms is documented from Middle Permian silicified peats of the Prince Charles Mountains, Antarctica, in the form of coprolites occurring both free in the peat matrix and clustered... more
Evidence for invertebrate feeding on glossopterid gymnosperms is documented from Middle Permian silicified peats of the Prince Charles Mountains, Antarctica, in the form of coprolites occurring both free in the peat matrix and clustered within excavations in roots, aerial wood and leaves. Observations of coprolites in thin-sections of the peats and from scanning electron microscopy of examples extracted via bulk maceration reveal nine morphotypes distinguished by size, shape, surface texture and contents. These include ...
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Research Interests: Geology and Earth Science
The Shangwang Basin is a small Cenozoic sedimentary basin located in Linqu county, Shangdong Province. The Shangwang Formation, especially the diatomaceous shale member, contains diverse and finely preserved flora and fauna fossils.... more
The Shangwang Basin is a small Cenozoic sedimentary basin located in Linqu county, Shangdong Province. The Shangwang Formation, especially the diatomaceous shale member, contains diverse and finely preserved flora and fauna fossils. Previous paleontological study and radiometric dating show it was formed in the Miocene. However, on the precise age of the formation, there are such different opinions as late Miocene, middle Miocene, or early stage of the Middle Miocene.
We have refined the age of the Shangwang Formation by means of geomagnetic polarity data combined with the latest results of radiometric dating as well as palynological analysis.
We have refined the age of the Shangwang Formation by means of geomagnetic polarity data combined with the latest results of radiometric dating as well as palynological analysis.
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Most knowledge concerning Mesozoic Era floras has come from compression fossils. This has been augmented in the last 20 years by rarer permineralized material showing cellular preservation. Here, we describe a new genus of anatomically... more
Most knowledge concerning Mesozoic Era floras has come from compression fossils. This has been augmented in the last 20 years by rarer permineralized material showing cellular preservation. Here, we describe a new genus of anatomically preserved gymnosperm seed from the Callovian–Oxfordian (Jurassic) Oxford Clay Formation (UK), using a combination of traditional sectioning and synchrotron radiation X-ray micro-tomography (SRXMT). Oxfordiana motturii gen. et sp. nov. is large and bilaterally symmetrical. It has prominent external ribs, and has a three-layered integument comprising: a narrow outer layer of thick walled cells; a thick middle parenchymatous layer; and innermost a thin fleshy layer. The integument has a longitudinal interior groove and micropyle, enveloping a nucellus with a small pollen chamber. The large size, bilateral symmetry and integumentary groove demonstrate an affinity for the new species within the cycads. Moreover, the internal groove in extant taxa is an autapomorphy of the genus Cycas, where it facilitates seed germination. Based upon the unique seed germination mechanism shared with living species of the Cycadaceae, we conclude that O. motturii is a member of the stem-group lineage leading to Cycas after the Jurassic divergence of the Cycadaceae from other extant cycads. SRXMT—for the first time successfully applied to fossils already prepared as slides—reveals the distribution of different mineral phases within the fossil, and allows us to evaluate the taphonomy of Oxfordiana. An early pyrite phase replicates the external surfaces of individual cells, a later carbonate component infilling void spaces. The resulting taphonomic model suggests that the relatively small size of the fossils was key to their exceptional preservation, concentrating sulfate-reducing bacteria in a locally closed microenvironment and thus facilitating soft-tissue permineralization.
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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with... more
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright a b s t r a c t The Lopingian coal measures of southwestern China were deposited within a range of facies associations spanning a spectrum of settings from fluvial to marine carbonate platform. The transitional to terrestrial coal measures are dominated by siliciclastics, but they also contain fifteen laterally extensive marine bands (limestone beds and mudstone). These bands act as marker horizons that enable correlation between fully marine and terrestrial facies. Examination of this range of facies and their sedimentology has enabled the development of a high-resolution sequence stratigraphic framework. Set against the established backdrop of second-order Lopingian transgression, sixteen fourth-order sequences and three composite sequences (third-order) are recognized. Results show that, in the composite sequences, peat accumulation in the seaward parts of the study area predominantly correlates with early transgressive sequence sets (TSS), while in more landward areas it correlates with the middle TSS to late highstand sequence sets (HSS). Differences in peat-accumulation regimes within the sequence stratigraphic framework are attributed to variations in subsidence and background siliciclastic input rates in different depositional settings, with these combining to produce differences in the rate of accommodation change. The preservation of coal resources in the middle to late HSS in this area was most likely related to the rise of the regional base level throughout the Lopingian.
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We document a new species of ovulate cone (Pararaucaria collinsonae) on the basis of silicified fossils from the Late Jurassic Purbeck Limestone Group of southern England (Tithonian Stage: ca. 145 million years). Our description... more
We document a new species of ovulate cone (Pararaucaria collinsonae) on the basis of silicified fossils from the Late Jurassic Purbeck Limestone Group of southern England (Tithonian Stage: ca. 145 million years). Our description principally relies on the anatomy of the ovuliferous scales, revealed through X-ray synchrotron microtomography (SRXMT) performed at the Diamond Light Source (UK). This study represents the first application of SRXMT to macro-scale silicified plant fossils, and demonstrates the significant advantages of this approach, which can resolve cellular structure over lab-based X-ray computed microtomography (XMT). The method enabled us to characterize tissues and precisely demarcate their boundaries, elucidating organ shape, and thus allowing an accurate assessment of affinities. The cones are broadly spherical (ca. 1.3 cm diameter), and are structured around a central axis with helically arranged bract/scale complexes, each of which bares a single ovule. A three-lobed ovuliferous scale and ovules enclosed within pocket-forming tissue, demonstrate an affinity with Cheirolepidiaceae. Details of vascular sclerenchyma bundles, integument structure, and the number and attachment of the ovules indicate greatest similarity to P. patagonica and P. carrii. This fossil develops our understanding of the dominant tree element of the Purbeck Fossil Forest, providing the first evidence for ovulate cheirolepidiaceous cones in Europe. Alongside recent discoveries in North America, this significantly extends the known palaeogeographic range of Pararaucaria, supporting a mid-palaeolatitudinal distribution in both Gondwana and Laurasia during the Late Jurassic. Palaeoclimatic interpretations derived from contemporaneous floras, climate sensitive sediments, and general circulation climate models indicate that Pararaucaria was a constituent of low diversity floras in semi-arid Mediterranean-type environments.
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The medullosan pteridosperm ovule Stephanospermum Brongniart is a well-known component of Carboniferous aged coal-ball and siderite nodule floras from North America and Europe but also occurs in the Permian floras of Cathaysia where it is... more
The medullosan pteridosperm ovule Stephanospermum Brongniart is a well-known component of Carboniferous aged coal-ball and siderite nodule floras from North America and Europe but also occurs in the Permian floras of Cathaysia where it is represented by the Lopingian (late Permian) aged species Stephanospermum trunctatum (Li) Wang et al. (2009) from coal-balls in the Wangjiazhai Formation in Southern China. We provide a detailed emendation of S. trunctatum and illustrate it comprehensively for the first time, and document an additional specimen from the Wangjiazhai Formation coal-ball assemblage that we assign to Stephanospermum shuichengensis sp. nov. S. shuichengensis is distinguished from S. trunctatum by the absence of apical teeth in the sclerotesta and non-obovate base. The two species of Stephanospermum from the Wangjiazhai Formation are important as they extend the stratigraphic and geographical range of the genus from the Pennsylvanian of Euramerica into the Lopingian of Southern China, and demonstrate that the genus persisted in wetland, peat forming environments in the run up to the end-Permian mass extinction event. The 44 MY stratigraphic discontinuity between the Euramerican and the Cathaysian species, here named the Stephanospermum gap, leads us to infer that the genus was likely to have occurred in the Pennsylvanian–Permian successions of southern Russia and northern China that are geographically and stratigraphically intermediate to the known occurrences but from which the genus has yet to be discovered. Medullosan pteridosperms appear to have become extinct at or immediately prior to the Permian–Triassic boundary that coincides with the Permo–Trias mass extinction event; although the exact causes of this loss in plant diversity remains unknown, a response to regional climatic drying is likely to have been a contributing factor.
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A new species of Medullosan ovule from the Mazon Creek Carboniferous lagerstätte is documented using a novel combination of non-invasive X-Ray Micro-Tomography (XMT) and orientated precision sectioning based on the XMT results. 3-D... more
A new species of Medullosan ovule from the Mazon Creek Carboniferous lagerstätte is documented using a novel combination of non-invasive X-Ray Micro-Tomography (XMT) and orientated precision sectioning based on the XMT results. 3-D reconstruction of the ovule has correlated geometries of different layers with tissue characteristics gathered from wafered sections, with the methodological combination presenting a virtual reconstruction of the specimen and also enabling positioning of serial sections of the holotype in pre-determined positions. Stephanospermum braidwoodensis sp. nov. has four longitudinally orientated sarcotestal wings, two to each side of the major plane that demonstrate 180° rotational (bilateral) symmetry, while the sclerotesta has three prominent longitudinal commissural ribs and the pollen chamber has three small ribs and triangular nucellar beak, both demonstrating radial (threefold) symmetry. This demonstration of both radial and bilateral symmetries in different tissues emphasises the complexities of inferring systematic affinities of fossil seeds from symmetry alone. We consider S. braidwoodensis to be closely related to the co-occurring S. konopeonus Drinnan et al., and postulate that it was born on a fertile truss similar to that of the latter species. Finally implications of our findings for the utility of these methods in identifying additional species from the Mazon Creek biota are discussed, and the advantages and disadvantages of different methods of nodule preparation are considered. We conclude that additional species are likely to be recognised from the Mazon Creek flora by application of the same methodologies used in this investigation.