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The end-Triassic mass extinction is considered one of the “Big Five” extinction events in the Phanerozoic. However, whether the terrestrial ecosystem began to deteriorate or even collapse prior to the Triassic–Jurassic (Tr-J) transition remains controversial. Compared with the documented data from the western Tethyan region, evidence from the eastern Tethyan realm is limited. We undertake a fitting analysis of the sedimentary system, floral community successions and major geological events of the Xujiahe Formation as reflected by the Qilixia Section, Xuanhan area, northeast Sichuan Basin, China. Our results reveal an oscillating fluvial-lacustrine depositional system during the Late Triassic, with the dominant sedimentary processes mainly controlled by the Indosinian Movement. Beside the sedimentary influence on the Xujiahe Flora, climate changes played a more important role. Fluctuating conditions to cooler and dryer climates at this time promoted diversification of gymnosperms under an overall warm and humid climate setting in the Late Triassic in the Xuanhan area. Superimposed on this oscillating long-term climate state, ecosystem destabilization occurred over 1 million years prior to the Tr–J interval in the Xuanhan study area, possibly in response to the intensified storm and wildfire activity and the following environmental changes. Although the Xujiahe Flora always recovered from the interruption of the tectonic movement, it ultimately collapsed under extreme climatic events and ecological pressures induced by the Late Triassic Central Atlantic Magmatic Province event.

As one of the hyperthermal events in the Mesozoic, the Carnian Pluvial Episode (CPE) was a global perturbation of the C-cycle and a strong enhancement of the hydrological cycle associated with global warming resulting in significant changes in sedimentary environments from Pangaea to deep water Panthalassa. In this paper, we make research on biostratigraphy, petrology, cyclostratigraphy and geochemistry of the Shemulong Formation in the Yanyuan Basin, at the southwestern of the Yangtze Platform. This strata record the complete deposition of the Carnian stage and preserve the signal of the astronomical orbital period. It also provides good paleontological information which was identified clear biostratigraphic framework. New redox proxies and stable isotopes are analyzed and compare the δ13C data with existing data from other sections of the CPE. In this section, there are at least four terrigenous input pulses which are consisted of sandstone and mudstone, causing the abrupt shutdown of carbonate production during the CPE period. Meanwhile, biodiversity data like bivalves, conodonts and ammonoids in the study area show a major change in abundance and variability during the CPE period. These are also coincident with negative carbon isotope excursions (NCIE), proving the close correspondence between the perturbation of the carbon cycle (and related hyperthermal events occur) and the turnover of depositional systems and ecosystems. Furthermore, we found differences in the recovery of carbonate production after each terrigenous input. The degree of recovery decreases and then increases upwards (bioclastic limestones - oolitic limestones - bioclastic limestones - biostrome - reef mound). It may link to the intensity of the terrigenous input pulse. In summary, this research provides more comparative schemes in the eastern Tethys for the collaborative study of environment biological co-evolution relationship within the CPE interval and is of positive significance for the in-depth understanding of climate and biodiversity changes through hyperthermal intervals in Earth history.AcknowledgementsThis work was supported by the National Natural Science Foundation of China (No. 41972120; 42172129), by the State Key Laboratory of Palaeo-biology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, CAS) (No.173131).

The aim of this study is to evaluate the thermal maturity of Upper Badenian (Middle Miocene) petroleum source rocks of the Getic Depression, Romania, and to characterize the dispersed organic matter using organic petrography associated with Rock-Eval pyrolysis. A total of 33 core samples of Upper Badenian source rocks from the central–southern part of Getic Depression was studied. The results show that most samples with values of total organic carbon (TOC) < 1% wt.% have a limited potential of hydrocarbons (HC) generation, and 30% of samples with TOC < 1.82 wt.% and kerogen type III, presenting particularly gas generation potential. In three samples from the Bibești, Grădiște and Socu structures the kerogen type III-II was identified, indicating the capability of oil and gas generation. The Badenian source rocks are thermally immature, as few samples are in the pre-oil window, with values of vitrinite reflectance (VRo%) ranging between 0.41% and 0.55%, and the values of Tmax between 409 °C and 443 °C. Optical microscopy with reflected white light and fluorescence blue light was used for identification of terrigenous macerals (vitrinite, liptinite as, resinite, cutinite, sporinite, and inertinite) associated with marine liptinite macerals (telalginite and lamalginite) showing yellow and bright–yellow epifluorescence.

Global climate and environmental changes were the main causes of the end-Triassic mass extinction. However, direct sedimentological evidence of environmental catastrophes is rare in Triassic – Jurassic interval, especially in the eastern Tethys region. The newly discovered in-situ trunk fossils in paleosol surface and a set of unique branch-supported sandstones below may record the environmental disaster at the Triassic-Jurassic interval in the northern Sichuan Basin. Sedimentological data showed the strong storm prevalent induced the lodging direction of in-situ trunks is opposite to the direction of paleocurrent. Enhancement of large-scale runoff along with the dramatic increase of woody detrital input may indicate the deforesting at the Triassic -Jurassic boundary in eastern Tethys, Sichuan Basin.

The end-Triassic mass extinction is one of the five big extinction events in the Phanerozoic, and its impact on marine organisms has been extensively studied. However, whether the terrestrial ecosystem had begun to deteriorate or even collapsed prior to the end-Triassic mass extinction remains controversial and the related studies in Asia are very limited. In this study, we provide a comprehensive investigation of the sedimentary environments, their implications for floral changes, and the paleoecology during the Norian–Rhaetian transition in Xuanhan area, northeastern Sichuan Basin, Southwest China. The sedimentary environments and climatic conditions changed coupling the transgression and regression caused by the tectonic movements. Climatic oscillations were identified during the Norian–Rhaetian transition in the Xuanhan area, including a short-term cooling event. The diversity and composition of the plant communities changed through the Norian–Rhaetian transition in Xuanhan area, but the terrestrial ecosystem as a whole didn’t collapse or deteriorate prior to the end-Triassic mass extinction.

The end-Triassic mass extinction (ETME) is considered to be one of the five most severe extinction events in Earth history and caused the disappearance of ca. 80% of all species. The terrestrial ecosystems were also greatly affected by this extinction, but the severity of the land plant diversity loss is not well understood. Ferns are once a principal component of the terrestrial ecosystem from the late Paleozoic/early Mesozoic era and colonizers taxa commonly found in disturbed environments. In this study, we investigated the diversity and ecology of fern during the Triassic-Jurassic (Tr–J) transition in the Sichuan Basin of South China and focused for the first time on the impact of the end-Triassic mass extinction event on the fern communities. We assembled fern fossil records in 16 localities from the Rhaetian Xujiahe (XJH) Formation to the lowermost Jurassic Zhenzhuchong (ZZC) Formation. Our results indicate that no obvious mass extinctions of macro-microflora of ferns but a clear species turnover was recorded at ETME in the Sichuan Basin, reflected an appropriate response of plants in places far away from CAMP volcanism. The paleoecological analysis based on macroflora and microflora in the Sichuan Basin shows a warm and humid condition of tropical-subtropical climate during Rhaetian followed by an increase of specific dry-resistant taxa, indicating a dryer environment at the Earliest Jurassic. Additionally, multivariate statistical approaches (principal coordinates analysis, cluster analysis, network analysis) for fern macro-remains and spores data in the southeastern Sichuan Basin infer that the members of XJH and ZZC Formation cluster in three groups, corresponding to their environmental conditions, determined by humidity and temperature.

International audience; Palaeobotany and palynology are the main direct sources of evidence for studying vegetation diversity dynamics through geological time. However, plant fossil diversity is affected by various factors other than vegetation diversity, which need to be taken into account in such studies. The use of fossil-taxa will potentially inflate perceived plant diversities, requiring taxonomic lists to be normalised. Autochthonous floras provide the most direct evidence of vegetation diversity but these are rare; most plant beds are allochthonous with plant remains that have been subjected to varying levels of fragmentation, transportation and time averaging. Local-scale vegetation diversity is especially difficult to determine from the fossil record, even with rigorous sampling protocols and detailed sedimentological analysis. Landscape-scale and regional-scale vegetation diversities are more reliably determined but usually at the rank of family. Macrofossil and palynological data tend to reveal evidence of different aspects of plant diversity, and the best results are obtained if the two diversity signals are integrated. Despite the inherent difficulties, the plant fossil record provides clear evidence of the dynamic history of vegetation through geological times, including the effects of major processes such as climate changes and mass extinctions

Successful evolutionary forms are characterized by their longevity in the fossil record. There are many plant groups that exhibit these traits; here we have selected the ferns as one acknowledged evolutionary model. Ferns are the most successful cryptogamic plants in geologic history and are known from nearly all fossil floras since their first appearance in the Devonian. Ferns, autotrophic organisms, have colonized nearly all types of continental environments over time [U1102]. Fern groups experienced rapid radiation at the familial level in the Carboniferous and are well documented in the fossil record thereafter. Their megaphyllous leaves are easy to recognize and have reproductive organs (sporangia filled by spores) borne on the lower side of pinnules. Although growth forms show great variability in morphology and size, all have retained this simple reproductive organization for over 400 million years from when first recognized in Devonian floras.

The aims of this study include the evaluation and interpretation of Oligocene source rocks from the Central-Western part of the Getic Depression, Romania, and the identification of their maturation and their hydrocarbon potential. 24 argillite samples belonging to the source rocks were studied using organic petrography and geochemistry methods, including Rock-Eval pyrolysis, and the following sets of results were obtained: maceral diversity, values of vitrinite reflectance, thermal alteration index, and organic geochemical values. The Oligocene disperse organic matter contains both, humic and terrestrial organic matter, as well as sapropelic, marine, algal matter, represented by telalginite and lamalginite. Several anoxic deep marine water intervals were recorded in the Getic Depression. The samples are immature, with Tmax values ranging between 415 °C and 434.5 °C, and random vitrinite reflectance of 0.32% and 0.53%. The samples yield a total organic content between 0.55% and 5.71%, with a hydrogen index between 9 and 379 mg/g, showing two types of kerogen: a. mixed type II-III kerogen, indicating a generative potential for hydrocarbon and gas, and b. type III kerogen, indicating a gas generative potential.

This paper aims to provide an up-to-date, realistic picture of the Romanian coal sector based on four interconnected perspectives: geological, economical, energy, and strategical. It reviews the latest data, evaluations, and reassessments regarding the potential of current resources and reserves, geological and petrographic aspects, current status of the coal mining industry, resource management, and analyzes the present national strategies in this field. This review provides some perspectives towards key aspects of the Romanian coal sector and builds a foundation for a more in-depth analysis and strategical development of the Romanian coal mining and management.

Determining the diversity of past floras helps with interpreting both the history and predicting the future of vegetation change. For global-scale and regional-scale diversity studies especially, secondary data are often used but local-scale studies tend to be based on survey data that require rigorous sampling. The correct sampling strategies depend on the types of fossils being investigated, including their physical size, and whether the aim is to determine taxonomic richness or relative abundance. Describing and comparing diversities can use a range of different metrics, depending on whether binary presence/absence or abundance data are available. Each metric provides a different insight into the diversities and the choice of which to use depends on the research question being investigated. Various numerical approaches are available for identifying spatial and stratigraphical diversity patterns, mainly classificatory techniques (e.g., cluster and parsimony analyses) and ordination (e.g., Detrended Correspondence Analysis, Nonmetric Dimensional Scaling). The choice of technique again depends on the research question, but often it has proved useful to run both types of analysis in tandem. This article is illustrated by past biodiversity case studies from throughout the fossil record, dealing with floras ranging in age from the Devonian to the last few centuries.

Anthrophyopsis Nathorst 1878 is a representative Late Triassic foliar genus with uncertain systematic affinities and poorly understood morphology and anatomy. Since its earliest report by Nathorst in 1878, 16 species have been documented worldwide. However, the taxonomic statuses of some taxa remain questionable. Out of 16 reported species, only three of them, including Anthrophyopsis crassinervis, A. tuberculata and A. venulosa can be retained as valid. Besides, four species, such as Anthrophyopsis brancai, A. miassica, A. narulensis and A. vachrameevii need further revision and investigation. Furthermore, nine species are invalid, including Anthrophyopsis decurrens, A. grandis, A. leeiana, A. multinervis, A. nilssoni, A. obovata, A. pilophorus, A. ripples and A. tenuinervis. The morphological diagnosis characters for genus Anthrophyopsis are detailed and updated, based on the new and well-preserved specimens from the Sichuan Basin, South China. A revision of historical collections and reported occurrences of this genus around the world was undertaken. Reviewing the valid species of Anthrophyopsis based on abundant Chinese material supports the emendation of the genus Anthrophyopsis and of its species. Stratigraphically, the occurrences of Anthrophyopsis are almost confined to the Upper Triassic, with only two questionable reports extending to the Lower Jurassic. The limited occurrences of valid Anthrophyopsis species in the Southern Floristic Province of China during the Late Triassic indicate that this genus represents a sensitive stratigraphic and palaeoclimatic marker.

The Haţeg and Rusca Montana basins (South Carpathians, Romania) yield a rich Late Cretaceous (Maastrichtian) compressive megafloral assemblage represented by ferns, conifers, monocotyledons and dicotyledons. This paper focuses on the dicotyledons of these basins, based on recently collected material as well as on historical collections of the University of Bucharest, including the Dinca and Raileanu collections, and of the Babes-Bolyai University of Cluj-Napoca, with the Petrescu and Dusa collection. The dicotyledonate association is represented by Araliaephyllum sp., Credneria denticulata , Ettingshausenia onomasta , Ettingshausenia sp., and five other dicotyledon types, a taxonomically much less diverse assemblage than previously published. Differences with regard to the previous taxa lists of the Haţeg and Rusca Montana basins are due to the reinterpretation of the fossil material in the light of recent advances in the field, especially when considering a higher variation of the leaf material, its preservation and its taphonomy.

The Lower Jurassic (Hettangian–Sinemurian) continental deposits of the Mehadia area (Caras–Severin County) belong to the Presacina Basin, Upper Danubian Units of the South Carpathians, Romania. This un-named succession is exposed along large areas within the Greaţca Quarry where deposits of a complex braided river system can be seen. Nine clastic facies are identified within the Mehadia section and grouped into two facies associations reflecting two main sub-environments. (A) a fine-grained association, up to 6.5 m thick, composed of greyish black and dark grey massive and horizontally laminated mudstones interbedded with fine- to medium-grained sandstones showing ripple lamination, tabular low-angle large-scale cross-bedding and in some places massive sandstones. Within this association coarsening and fining-upward sequences are visible, while subordinate pensymmetrical-like sequences were observed. The sediments of the fine-grained association are interpreted as having been deposited along an alluvial plain from flood waters. The sandstone interbeds are interpreted as crevasse channel-fills and the thinner sandstone bodies as proximal crevasse splays. (B) a coarse-grained facies association represented by sandstones and conglomerates, both clast- and matrix-supported, from granule to pebble clast sizes. Almost all basal members of this association are underlain by erosional surfaces, while internal erosional surfaces occur at some levels. The coarse-grained facies association is interpreted as having been deposited within active river channels of a sandy braided river system. The occurrence of numerous erosional surfaces, the recurrence of the facies within this association (channel bodies), as well as the abundant mudstone and sandstone intraclasts all point to frequent conditions of erosion (including redeposition) of previously deposited sediments. The relatively low fine-grained sediment content (

Two Early Jurassic localities, the Mecsek Mts in Hungary and Anina in Romania, are similarly significant and both floras are of autochthonous/paraautochthonous origin. In the Early Jurassic the Hungarian locality was a delta plain; the Romanian locality was an intramontane depression filled predominantly by a braided river system. The floristic composition of the two localities (52 genera, 120 species), although superficially similar (25 common genera), differs at species level (only 9 common species) as well as in the proportions of taxa in major plant groups. These differences can be explained by differences in environmental conditions resulting from palaeogeographic and topographic factors. Based on previous and recent studies, alpha diversity as well as statistically (DCA, PCA) differentiated ecogroups are compared and discussed. For common species, the GLM method was used to classify them to particular environmental response types. Their environmental requirements in both ecosystems are evaluated. Some of the shared species showed different preferences at the localities, explainable by their broad ecological tolerance.

The Jurassic floras of Europe show considerable diversity. To examine the extent of this diversity and its possible causes we used multivariate statistical methods (cluster analysis, PCA, NMDS) to compare all significant Jurassic floras in Europe. Data were based on 770 taxa from 46 fossiliferous occurrences (25 units) from France, Germany, Greenland, Hungary, Italy, Norway, Poland, Romania, Scotland, Serbia, Sweden, Switzerland, and the United Kingdom. Statistical analyses were applied at species level and genus level, and also performed for the major plant groups. The genus cladograms show affinities between different localities based on environmental factors, while the cladograms based on species affinities indicate only taxonomical correlations. The study shows that locality age does not seem to be of paramount importance for floral composition.

The Carboniferous Cucuiova Formation of the Sirinia Basin, Danubian Units, in Almăj Mountains, South Carpathians, yields a highly diverse yet rare compressive flora representing significant heritage values of the “Iron Gates” Natural Park. This flora includes pteridophytes (lycopsids, sphenopsids, filicopsids) and gymnosperms (pteridosperms and conifers), some of these representatives being important coal generators during the Late Carboniferous times. The facies features, distribution and paleofloral features of the Cucuiova Formation are discussed in the framework of the Sirinia Basin. The lycopsid Lepidophloios acerosus Lindley and Hutton 1831 is reported for the first time in Romania from the Cucuiova Formation in Dragosela Valley, in the central part of the “Iron Gates” Natural Park.

The Romanian Early Jurassic (Hettangian–Sinemurian) floras represent a key element of the Eurosinian Province in which the Williamsoniaceae (Bennettitales) are well represented by vegetative remains (leaves, stems, roots) and reproductive structures. Up to the present, Early Jurassic bennettitalean reproductive structures have been found at only two localities in Romania: Anina and Doman. These localities belong to the Resiţa Basin, Getic Nappe, South Carpathians, Romania, with Anina considered to be the best Romanian Early Jurassic locality in terms of diversity and preservation of fossil plants and animals, i.e. a fossil Lagerstatte. This paper deals with all bennettitalean reproductive structures identified to date. These belong to the Steierdorf Formation, Valea Tereziei Member, and are Sinemurian in age. In total, 32 rare hand specimens (compressions and casts) have been studied and the following taxa identified: Williamsonia banatica Krasser, W. latecostata Semaka, Bennetticarpus sp. A and sp. B, Cycadolepis sp., Weltrichia alfredii Krasser, Weltrichia givulescui Popa, 2001, Weltrichia johannae sp. nov., Weltrichia antonii sp. nov., Weltrichia steierdorfensis sp. nov., Weltrichia sp. A and Weltrichia sp. B. The systematic affinities of these taxa are discussed, as well as aspects related to their stratigraphy and palaeocology.

Very large, sparsely distributed, sinuous, gently dipping and occasionally branching tunnels with subordinate swells, as well as possible chambers and scratches, are described from the Hettangian Dealul Budinic Member of the Lower Jurassic continental Steierdorf Formation at Anina in the South Carpathians, Romania, and are interpreted as tetrapod burrows. No bone remains have been found in association with these structures. The morphology and large dimensions of the burrows suggest that the trace-makers were sauropsid amniotes, most probably either crocodyliforms or small-sized basal neornithischian dinosaurs, although their therapsid affinities, despite being less likely, cannot be discarded either. The age, large size and probable origin of these burrows add important information to a poorly documented period of the evolution of tetrapod fossoriality. It may be suggested that within a relatively short time interval following the Triassic-Jurassic extinction event, when environmental conditions were still marked by strongly seasonal climate with prolonged droughts as well as extreme moisture and temperature fluctuations, fossorial habit probably became yet again an endurance strategy for burrow makers.

Community level ecology is considered to support significantly the recognition of the ecological status of plant taxa and the identification of plant ecogroups, thus it generally provides extended data sets on the spatial and temporal changes of ecological factors. Since research based exclusively on plant structure and their supposed adaptation to the environment is now considered inadequate, statistical methods can be used. Assuming that co-occurrence of plant fossils on a single hand specimen in the case of autochthonous or parautochthonous floras is the result of their growth in the same phytocenosis, quantitative ecological analysis on Mesozoic materials would yield significant insights. In this paper, statistical and multivariate quantitative analyses of Early Jurassic plant fossil records from the Steierdorf Formation in Anina (South Carpathians, Romania) are presented. Four palaeoecological groups of taxa were distinguished by principal component analysis (PCA) and interpreted as plant assemblages of various palaeobiotopes associated with the sedimentary facies of the enclosing formation. A group of samples was analysed using the principal coordinate (PCO) method and the statistical significance (p {less than or equal to} 0.05) (p ≤ 0.05) of individual binary responses of taxa along the first two PCO ordination axes was tested by general linear model (GLM). They revealed putative palaeoecological gradients: axis 1 – disturbance caused by water level fluctuations, axis 2 – temperature, corresponding with the already assumed environmental and climatic change at the Hettangian/Sinemurian boundary. Multivariate analyses enabled the identification of palaeoecological groups and thus inferring palaeogeographical conditions based on Mesozoic materials.

Bennettites are an abundant and frequently well-preserved component of many Mesozoic fossil floras, often playing an important ecological role in flood plain vegetation communities. During a recent ...

Newly collected Rhaetian plant compressions of the seed fern Ptilozamites nilssonii Nathorst 1878 from Jameson Land, Eastern Greenland, revealed both simple and forked, unipinnate and bipinnate morphologies, indicating a closer relationship between the genera Ptilozamites Nathorst 1878 and Ctenozamites Nathorst 1886 than previously documented. Cuticle analysis revealed micromorphological traits typical of simply pinnate P. nilssonii on bipinnate leaf forms, yet up until the discovery of this material Ptilozamites has never been considered bipinnate. In 1886, the genus Ctenozamites was erected for species similar in epidermal characters to Ptilozamites, but presenting a typical bipinnate character, rarely or never unipinnate. As the new Greenland material collected from South Tancrediakloft and Astartekloft have shown, both genera are now very strongly related anatomically, and therefore identical from a systematic point of view. We therefore propose the use of the genus Ptilozamites as Ctenozamites Nathorst 1886 is a synonym of Ptilozamites Nathorst 1878.

The Lower Jurassic (Sinemurian) deposits of Cristian (Brasov County, Romania) contain a well-preserved land flora. Pachypteris gradinarui n.sp., a new species of seed fern foliage belonging to the Corystospermales, is described, figured and analysed. The species has a bipinnate, petioled frond; secondary rachises inserted on the upper side of the primary rachis; rounded, occasionally lobed pinnules without marked abaxial thickening or folding. The material is compared with other Pachypteris species, and with Cycadopteris, a related genus characterised by marginal (cuticular) thickening and folding, as it presents transitional characters between the two genera.

A new fern genus belonging to the Matoniaceae (Order Filicales) is described under the name of Aninopteris Givulescu et Popa, gen. nov. , with the type species A. formosa Givulescu et Popa, sp. nov . The fossil material is early Liassic in age (late Hettangian–Sinemurian) and comes from Anina, the Steierdorf Formation, Caras-Severin County, Romania. The new genus and species are compared to species of the genus Phlebopteris , from a macro- and microscopical (in situ spores) point of view. The preservation of the fossil material is very good. This permitted the extraction of the spores from the fertile material of the fern and examination under light microscopy.

The magnitude and pace of terrestrial plant extinction and macroecological change associated with the Triassic/Jurassic (Tr/J) mass extinction boundary have not been quantified using paleoecological data. However, tracking the diversity and ecology of primary producers provides an ideal surrogate with which to explore patterns of ecosystem stability, collapse, and recovery and to explicitly test for gradual versus catastrophic causal mechanisms of extinction. We present an analysis of the vegetation dynamics in the Jameson Land Basin, East Greenland, spanning the Tr/J extinction event, from a census collected paleoecological data set of 4303 fossil leaf specimens, in an attempt to better constrain our understanding of the causes and consequences of the fourth greatest extinction event in earth history. Our analyses reveal (1) regional turnover of ecological dominants between Triassic and Jurassic plant communities, (2) marked structural changes in the vegetation as reflected by potential loss of a mid-canopy habit, and (3) decline in generic-level richness and evenness and change in ecological composition prior to the Tr/J boundary; all of these findings argue against a single catastrophic causal mechanism, such as a meteorite impact for Tr/J extinctions. We identify various key ecological and biological traits that increased extinction risk at the Tr/J boundary and corroborate predictions of meta-population theory or plant ecophysiological models. These include ecological rarity, complex reproductive biology, and large leaf size. Recovery in terms of generic-level richness was quite rapid following Tr/ J extinctions; however, species-level turnover in earliest Jurassic plant communities remained an order of magnitude higher than observed for the Triassic. We hypothesize, on the basis of evidence for geographically extensive macrofossil and palynological turnover across the entire Jameson Land Basin, that the nature and magnitude of paleoecological changes recorded in this study reflect wider vegetation change across the whole region. How exactly these changes in dominance patterns of plant primary production affected the entire ecosystem remains an important avenue of future research. © 2007 The Paleontological Society. All rights reserved.

International audience; Palaeobiogeography plays an important role in the evolution of continental plants. This has been demonstrated mainly for modern biota and for past biota on a very large scale only. During the Jurassic–Early CretaceousMid-Eastern Europe was an archipelago, thus a particularly suitable area for a more detailed study. We investigated the area's plant palaeobiogeography, using fossil wood, with information from both a literature survey and investigation of new samples. There is a clear north–south differentiation of wood floras. The northern part of the archipelago, which was connected by a shallow sea, has a homogenous flora. A small terrane in the south, separated by true oceanic crust, seems to have had a peculiar flora, lacking widely distributed elements but displaying an endemic taxon with Gondwanan affinities. Compared toWestern Europe,Mid-Eastern Europe has a Jurassic–Early Cretaceous wood flora with similar diversity, except for the Late Jurassic, when it was limited to a single taxon, the widespread Agathoxylon Hartig. The wood flora of northern Gondwana is less diverse across the time interval under consideration, except for the Late Jurassic again. Taphonomic bias cannot be ruled out, but this low diversity during the Late Jurassic suggests stressful climatic conditions for Mid-Eastern Europe.

Exceptional preservation of extinct Pachypteris extra-epidermal cuticle enabled the first detailed statistical measurements of its ultrastructure using transmission electron microscopy. Pachypteris is a leaf genus of the Mesozoic belonging to seed fern foliage of the order Corystospermales. The species studied in this paper is Pachypteris gradinarui Popa [Rev. Palaeobot. Palynol. 111 (2000) 31], based on fossils which are Early Jurassic in age (Hettangian-Sinemurian, approximately 205-190 million years old). Both the upper and the lower cuticles were thoroughly examined, including the detail of the stomatal complexes and epidermal cells. The data obtained from our TEM analysis, together with the confidence intervals, were very useful to give precise description of the cuticles as they distinguished between upper and lower epidermal and stomatal cell types. Moreover a combination of characters was used to develop the first dichotomous key based on ultrastructural characters, i.e. not only the total thickness of the cuticle but also details and proportions of A cuticle proper and B cuticular layer. Comparisons with ultrastructures known from other Pachypteris species show that the influence of space and time, diagenetic processes, and/or processes related to technical procedures, seem to be minimal within this genus. Detailed studies of this type may be very useful for further comparisons among other species and at higher taxonomical ranks.