Monosulcate Pollen Research Articles

Confirmation that Antevsia zeilleri microsporangiate organs associated with latest Triassic Lepidopteris ottonis (Peltaspermales) leaves produced Cycadopites-Monosulcites-Chasmatosporites- and Ricciisporites-type monosulcate pollen

In reply to the commentary by N. Zavialova (Rev. Palaeobot. Palynol. 322, 105,065), we provide additional data and illustrations reaffirming that the Triassic peltaspermalean ‘seed-fern’ Lepidopteris ottonis produced the abnormal pollen Ricciisporites tuberculatus, solving a long-standing mystery in palaeobotany. The microsporangiate organ Antevsia zeilleri linked to Lepidopteris ottonis foliage produced polymorphic pollen ranging from smooth-walled monads that would normally be attributed to Cycadopites, Monosulcites and Chasmatosporites to strongly ornamented Ricciisporites tuberculatus-type grains occurring in permanent tetrads. Multiple microscopy techniques reveal that these in situ and associated dispersed pollen are represented by a complete continuum in exine ornamentation. Moreover, scanning electron microscopy and ultrastructural analyses reveal variation in the wall architecture between these pollen types that can be explained by aberrant developmental pathways within the pollen sac. Finally, the occurrence of Ricciisporites tuberculatus in at least 15 Antevsia zeilleri sacs and their co-occurrence with smooth-walled monosulcate pollen in an additional five pollen sacs, in the absence of any other palynomorphs, plant detritus or mineral matter, demonstrates their co-production by the parent plant and excludes the possibility of taphonomic mixing.

The ‘seed-fern’ Lepidopteris mass-produced the abnormal pollen Ricciisporites during the end-Triassic biotic crisis

The end-Triassic mass extinction (ETE; ~201.6 million years ago) led to dramatic changes in terrestrial ecosystems including the extinction of several seed-plant groups. Among the most intriguing features in the vegetation signal is the dominance of the peculiar pollen, Ricciisporites tuberculatus Lundblad, across large areas of the Northern Hemisphere immediately prior to and during the ETE. The parent plant of this pollen has remained unknown for 70 years. Here, we demonstrate that the ‘seed-fern’ Lepidopteris ottonis (Göppert) Schimper (Peltaspermales) produced R. tuberculatus in permanent tetrads. We show that R. tuberculatus is a large, abnormal form of the small smooth-walled monosulcate pollen traditionally associated with L.ottonis, which disappeared at the ETE, when volcanism induced cold-spells followed by global warming. We argue that the production of aberrant R. tuberculatus resulted from ecological pressure in stressed environments that favoured asexual reproduction in peltasperms. The expansion of dry environments led to the dominance of drought-tolerant plants in the Early Jurassic of northern middle latitudes.

Palynological evidence for the Middle Jurassic environmental evolution in the eastern part of the Alborz Mountains (northern Iran)

The palynological assemblages of the Dalichai Formation were studied to reconstruct the paleoenvironmental evolution of the Middle Jurassic interval in the eastern part of the Alborz Mountains (N Iran). Dinoflagellate cyst biozones, planktonic foraminifera, and ammonites suggest a Bajocian-Callovian age for the Dalichai Formation. The palynodebris, mostly of terrestrial origin, are dominated by black opaque phytoclasts. Dinocysts, spores, pollen grains, and amorphous organic matters (AOM) are minor components in most samples. Terrestrial palynoflora are mainly represented by coastal gymnosperms (Araucariaceae, Cheirolepidiaceae), lowland simple monosulcate pollen producers (Cycadales/Bennettitales), ferns, upland seed ferns and conifers (Corystospermales and other bisaccate pollen producers). These assemblages indicate a warm climate with seasonally-dry conditions. However, an increase in Cheirolepidiaceae (Classopollis) in Bathonian assemblages reflects higher temperature during this interval. The dominance of the land-derived phytoclasts and presence of brackish water Botryococcus colonies with cells arranged irregularly suggest a proximal setting with high terrestrial and freshwater input during the Bajocian. The palynofacies analysis suggests a sea-level rise during the Bathonian, reflected by higher abundance and diversity of dinocysts as well as the presence of degraded small phytoclasts. This transgression phase is related to the increased subsidence of the Alborz region due to ongoing Neotethys subduction and creation of a large extensional back arc basin in the Eurasian margin. The syn-rift deposits are characterized by ammonitico rosso facies as well as hemipelagic carbonates containing planktonic foraminifera and pelagic bivalves.

Vegetation and climate change at the southern margin of the Neo-Tethys during the Cenomanian (Late Cretaceous): Evidence from Egypt.

Changes in terrestrial vegetation during the mid-Cretaceous and their link to climate and environmental change are poorly understood. In this study, we use plant macrofossils and analysis of fossil pollen and spores from the Western Desert, Egypt, to assess temporal changes in plant communities during the Cenomanian. The investigated strata have relatively diverse sporomorph assemblages, which reflect the nature of parent vegetation. Specifically, the palynofloras represent ferns, conifers, monosulcate pollen producers, Gnetales, and a diverse group of angiosperms. Comparisons of both, dispersed palynoflora and plant macrofossils reveal different characteristics of the palaeoflora owing to a plethora of taphonomical and ecological biases including the depositional environment, production levels, and discrepancies between different plant organs. A combination of detailed records of sporomorphs, leaves, and charcoal from the studied successions provide new understandings of the palaeoclimate and palaeogeography during the Cenomanian and Albian-Cenomanian transition in Egypt. The mixed composition of the palynofloral assemblages reflects the presence of different depositional situations with a weak marine influence, as evidenced by a minor dinoflagellate cysts component. The local vegetation comprised various categories including herbaceous groups including ferns and eudicots, fluvial, open environments, and xeric arboreal communities dominated by Cheirolepidiaceae and perhaps including drought- and/or salt-tolerating ferns (Anemiaceae) and other gymnosperms (Araucariaceae, Ginkgoales, Cycadales, and Gnetales) as well as angiosperms. The presence of riparian and freshwater wetland communities favouring aquatic and/or hygrophilous ferns (of Salviniaceae and Marsileaceae), is noted. The wide variation of depositional settings derived from the palynological data may be attributed to a prevalent occurrence of producers in local vegetation during the early Cenomanian of Egypt. For the purpose of this work on the studied Bahariya Formation and its equivalent rock units, where iconic dinosaurs and other fossil fauna roamed, we attempt to improve the understanding of Egypt's Cenomanian climate, which is reconstructed as generally warm and humid punctuated by phases of considerably drier conditions of varying duration.

On the exine ultrastructure of fossil ginkgoaleans: In situ pollen of Sorosaccus Harris

The morphology and exine ultrastructure have been studied of pollen grains from pollen cones of Sorosaccus sibiricus Prynada from the Ust’-Baley (Aalenian, Siberia), Sorosaccus sp. from the Vladimirovka (Aalenian-Bajocian, Siberia), and S. ex gr. sibiricus Prynada from the Tyrma (Tithonian–Berriasian, Russian Far East) localities. The pollen grains are boat-shaped and monosulcate. A finely granulate pattern is discernible under high magnification of light microscope in pollen grains from Vladimirovka and Tyrma; SEM shows that this pattern is formed by flat verrucae. TEM shows that sculptural elements are present on the surface of pollen grains from Ust’-Baley, although it is not evident in LM and SEM. By previous data on modern and fossil members, we believed that ginkgoalean pollen grains can be differentiated from similar boat-shaped monosulcate pollen of other affinities by a ratio of ectexinal sublayers (a thick homogeneous tectum, a thin infratectum of one row of structural elements, and a thin foot layer) in combination with an ectexine that is greatly reduced in the aperture region. Freshly obtained data have revealed another set of characters, with a less prominent tectum by comparison to underlying sublayers, an infratectum with small granules within the alveoli, and a prominent verrucate surface pattern that is distinguishable even in transmitted light. Ginkgoaleans are characterized by more than one set of ultrastructural characters of the exine.

Multivariate analysis of Lower Cretaceous monosulcate pollen from central-western Argentina

Monosulcate pollen grains are an important component of the Mesozoic palynofloras around the world. These type of grains are produced by several groups of plants and because of the morphological similarities among them, their taxonomic determination is difficult. Currently, there is scarce information about morphological differences of monosulcate pollen grains and this makes their botanical affinity in fossil specimens challenging. In this work, we analyzed statistically the morphological features of monosulcate fossil pollen grains recovered from six palynological assemblages from the Lower Cretaceous Lagarcito Formation of central-western Argentina. We used our own fossil dataset and data from the description of monosulcate pollen grains published from Cretaceous cycadalean in situ male cones from Patagonia. Furthermore, morphological variables from selected living species were added to support the analysis. According to our results, two main groups with clear morphological features were characterized among fossils. The use of an extant dataset allowed us to support the exine sculpture as an important variable when characterizing fossil pollen grains. Finally, our fossil dataset showed similarities with the in-situ pollen grains from the cycadalean cone species Androstrobus munku and Androstrobus patagonicus. This work is the first attempt to identify different morphological types among fossil monosulcate pollen grains recovered from the Lagarcito Formation of central-western Argentina. Our results will contribute to elucidate morphological variations in fossil pollen grains and may improve future taxonomic studies.

Palynological diversity of highly medicinal rare, endangered, and threatened plants from Western Himalaya, India

The present study investigated the palynological diversity of highly medicinal Rare, Endangered, and Threatened (RET) plant species dwelling in higher altitudes of Western Himalaya, India. The pollen morphology of 32 plant species covering 29 genera, 23 families, and 18 orders of Angiosperms was analyzed by Light Microscopy (LM) and Scanning Electron Microscopy (SEM). The families of the studied plant species have been arranged and discussed following the evolutionary sequence as per the updated version of Angiosperm Phylogeny Group ІV. The studied pollen characters were found to be helpful in the delimitation of taxa at the species level. In the studied monocots, the species belonging to order Zingiberales, Asparagales, and Liliales followed the general trend of having primitive inaperturate to advance monosulcate pollen except for Alismatales which had inaperturate pollen and placed after the orders mentioned above in the APG ІV classification system. The pollen aperture of the eudicot group in the present study followed the evolutionary pattern from tricolpate to tricolporate and triporate, which corroborated previous reports. All the investigated species of both monocot and eudicot groups had monad pollen units suggesting their primitiveness on the evolutionary scale except for the Rhododendron companulatum (Ericales), having evolutionarily advanced tetrad arrangement. The current study found primitive exine ornamentation in Ranunculales to advance in Asterales, Lamiales, Gentianales, and Boraginales and confirms the results of the previous studies. The data on the pollen morphological features of the studied species generated in the present study will help understand these important high-altitude plant species' reproductive biology and conservation aspects.

A palynological study of Dioscorea (Dioscoreaceae) in Korea

A palynological study of genus Dioscorea L. in Korea was conducted to evaluate the taxonomic implications. As a result of confirming the palynological characteristics of seven taxa of Dioscorea L., including six that are distributed in Korea and D. tokoro found in Japan, sections or species were classified according to the characteristics, such as the number of apertures, the polar end shape, and exine sculpturing. Specifically, the exine sculptures of D. coreana and D. tokoro, erroneously known to be distributed in Korea, are distinguished. The change in the number of apertures is closely associated with microsporogenesis, and it can be presumed that disulcate pollen might have been derived from monosulcate pollen in Dioscorea.

<p><strong>Pollen morphology of Indian <em>Aponogeton</em> (Aponogetonaceae, Alismatales) and the problem of recognizing palynotypes in a taxonomically diverse and ancient genus</strong></p>

Monogeneric Aponogetonaceae is sister to the rest of tepaloid core Alismatales and its members are characterized by a number of plesiomorphic features including monosulcate pollen. A recent study documented the earliest fossil pollen records of Aponogeton in late Cretaceous and early Cenozoic as well as recognized six pollen types in the genus. However, there are remaining gaps in palynological investivation of Aponogeton species. We present data on eight Indian species of the genus. Pollen of Aponogeton appendiculatus, A. crispus, A. bruggenii, A. microphyllus, A. natans, A. nateshii and A. wolfgangianus is reticulate with quite small lumina of irregular shape with short, convex and wide muri bearing small (up to 0.5 μm) echini. Pollen of Aponogeton satarensis clearly differs from that of the rest of examined species in larger lumina and muri bearing large (0.8–1 μm) and wide conical echini. These palynological differences fit well with molecular phylogenetic data and earlier ideas based on gross morphology. Our data suggest that although exine sculpturing is taxonomically significant in Aponogeton, the use of size of echini as a character distinguishing some palynotypes is problematic. Quantitative characters such as equatorial diameter and polar axis length showed no clear differences between examined species, but differences were found between analyzed samples (more precise, individuals) of the same species. Our new data support the earlier conclusion on the homoplastic nature of pollen evolution in Aponogeton.

A new monosulcate pollen from the Early Cretaceous of central-western Argentina

A new monosulcate species, Shanbeipollenites lagarcitensis sp. nov. is described from the Lower Cretaceous Lagarcito Formation, Sierras de Guayaguas (north-western San Luis Basin), Argentina. Shanbeipollenites lagarcitensis shares with other species of this genus a broadly ellipsoidal outline and a diagonally disposed distal sulcus. However, the new species differs from the psilate type species Shanbeipollenites quadrangulatus and from S. quadratus by the presence of sculptural elements distributed at the equatorial region, close to the opposite ends of the sulcus. The thicker wall, exine separation, much more strongly diagonal offset of the sulcus and the rugulate-verrucate sculpture with an equatorial distribution close to the opposite ends of the sulcus, distinguish this new species and expands the concept of the genus Shanbeipollenites. The presence of two separate exine layers supports its gymnosperm affinity. Furthermore, the occurrence of Shanbeipollenites lagarcitensis in the Albian Lagarcito Formation from mid–latitudes, central–western Argentina constitutes the youngest record of the genus worldwide. This new record expands the biostratigraphical range of the taxon into the Albian.

Среднеюрские растения-углеобразователи Улуг-Хемского бассейна (Республика Тыва, Россия)

Dispersed cuticles of plants from coals of the Middle Jurassic Ulugkhem Formation (locality 229 near Mount Begreda, Ulug-Khem Basin, Republic of Tyva) were studied. As a result of the study of mesofossils using light and scanning electron microscopes, it was found that the coals are composed mainly of the remains of ginkgophytes. They are represented by the leaves of Pseudotorellia cf. angustifolia Doludenko, the female reproductive organs of this plant Umaltolepis sp., as well as the leaves of Eretmophyllum neimengguensis Li, Sun, Wang, Dilcher, Tan, Li, Na. The conifers played subordinate role. The palynospectrum of the coal seam is dominated by the spores of ferns; bisaccate and monosulcate pollen are next in importance. Thus, ginkgophytes and ferns predominated in the Middle Jurassic swamp communities in the Ulugh-Khem Basin. For the first time, the coal-forming role of the genus Eretmophyllum was revealed. The Middle Jurassic flora of Tyva is similar to the floras of the Kansk-Achinsk and Irkutsk basins of Eastern Siberia, Angren Basin of Uzbekistan, and the Ordos Basin of Inner Mongolia, China by predominance of Pseudotorellia. The vegetation was clearly differentiated into the lowland and the slope one. In the latter the leptostrobaleans, ginkgoaleans, and conifers were represented. Pseudotorellia is one of the main components of swamp plant communities in the more northern regions: in the Ulug-Khem and Irkutsk basins, and in the Aban and Pereyaslovka coal fields of the Kansk-Achinsk Basin. This genus disappears in the Nazarovo coal field of the Kansk-Achinsk Basin, being replaced by the leptostrobaleans. Here the compositions of swamp and slope communities practically do not differ. The Late Mesozoic swamp plant communities were characterized by conservatism, as well as by extreme sensitivity to environmental changes, which apparently developed because of their existence in the same conditions of high humidity. Degradation of the swamps led to the disappearance of swamp plant communities.

Dinosaur-plant interactions within a Middle Jurassic ecosystem\u2014palynology of the Burniston Bay dinosaur footprint locality, Yorkshire, UK

Dinosaur footprints are abundant in the Middle Jurassic Ravenscar Group of North Yorkshire, UK. Footprints are particularly common within the Bathonian Long Nab Member of the Scalby Formation and more so within the so-called ‘Burniston footprint bed’ at Burniston Bay. The Yorkshire Jurassic is also famous for its exceptional plant macrofossil and spore-pollen assemblages. Here we investigate the spore-pollen record from the dinosaur footprint-bearing successions in order to reconstruct the vegetation and assess possible dinosaur-plant interactions. We also compare the spore-pollen assemblages with the macroflora of the Scalby Ness Plant Bed, which occurs within the same geological member as the Burniston succession. The spore-pollen assemblages are dominated by Deltoidospora spp., the majority of which were probably produced by Coniopteris. Lycophyte spores (including megaspores) are common in the Yorkshire Jurassic, but lycophyte parent plants are extremely poorly represented in the macroflora. Seed ferns, represented by Alisporites spp., are moderately abundant. Conifer pollen assemblages are dominated by Araucariacites australis (probably produced by Brachyphyllum mamillare), Perinopollenites elatoides and Classopollis spp., with additional bisaccate pollen taxa. Abundant Ginkgo huttonii in the macroflora suggests that much of the monosulcate pollen was produced by ginkgoes. The diverse vegetation of the Cleveland Basin presumably represented an attractive food source for herbivorous dinosaurs. The dinosaurs probably gathered at the flood plains for fresh-water and also used the non-vegetated plains and coastline as pathways. Although assigning specific makers to footprints is difficult, it is clear that a range of theropod, ornithopod and sauropod dinosaurs inhabited the area.

Pseudoasterophyllites cretaceusfrom the Cenomanian (Cretaceous) of the Czech Republic: A possible link between Chloranthaceae andCeratophyllum

AbstractPseudoasterophyllites cretaceus from the Cenomanian of Bohemia was recently recognized as an angiosperm by association with stamens containing monosulcate pollen of the Tucanopollis type. New material indicates that the stamens were borne in short spikes, with each stamen subtended by a bract, whereas the carpels were solitary and contained a single pendent, orthotropous ovule. We have investigated the phylogenetic position of Pseudoasterophyllites by including it in a morphological analysis of extant angiosperms using backbone constraint trees that represent the current range of hypotheses on relationships of the five mesangiosperm clades. With a backbone tree in which Chloranthaceae are linked with magnoliids and Ceratophyllum with eudicots, the most parsimonious position of Pseudoasterophyllites is sister to Chloranthaceae, but a sister‐group relationship to Ceratophyllum is only one step less parsimonious. With a backbone tree in which Chloranthaceae and Ceratophyllum form a clade, Pseudoasterophyllites is sister to Ceratophyllum, based on derived features shared with both Chloranthaceae and Ceratophyllum plus solitary female flowers (as in Ceratophyllum). Similar results are obtained when Pseudoasterophyllites is added to the analysis with other fossils inferred to be related to Chloranthaceae and/or Ceratophyllum. If the plants that produced Tucanopollis pollen in the Barremian‐Aptian of Africa–South America are related to Pseudoasterophyllites, these results suggest that Chloranthaceae and Ceratophyllum are relicts of one of the most important early radiations of angiosperms, which included not only colonizers of disturbed terrestrial habitats but also halophytes and aquatics.

Ultrastructural aspects of pollen ontogeny in an endangered plant species, Pancratium maritimum L. (Amaryllidaceae).

Pollen ontogeny in Pancratium maritimum L. was studied from the sporogenous cell to mature pollen grain stages using transmission electron, scanning electron, and light microscopy to determine whether the pollen development in P. maritimum follows the basic scheme in angiosperms or not. In the course of microsporogenesis and microgametogenesis, special attention was given to the considerable ultrastructural changes that are observed in the cytoplasm of microsporocytes, microspores, and mature pollen grains throughout the successive stages of pollen development. Microsporocyte differentiation concerning number and ultrastructure of organelles facilitates the transition of microsporocytes from the sporophytic phase to the gametophytic phase. However, cytoplasmic differentiation of generative and vegetative cells supports their functional distinctness and pollen maturation. Although microsporogenesis and microgametogenesis in P. maritimum generally follow the usual angiosperm pattern, abnormalities such as formation of unreduced gametes were observed. During normal microsporogenesis, meiocytes undergo meiosis and successive cytokinesis, resulting in the formation of isobilateral, decussate, and linear tetrads. Subsequent to the development of free and vacuolated microspores, the first mitotic division occurs and bicellular monosulcate pollen grains are produced. Pollen grains are shed from the anther at binucleate stage. During pollen ontogeny, three periods of vacuolization were observed: in meiocytes, in mononucleate free microspores, and in the generative cell.

Middle Jurassic vegetation dynamics based on quantitative analysis of spore/pollen assemblages from the Ravenscar Group, North Yorkshire, UK

AbstractQuantitative analysis of the distribution of dispersed spores and pollen (sporomorphs) has been used to assess temporal floral variation through the Middle Jurassic Ravenscar Group (Aalenian–Bathonian), North Yorkshire, UK. Aalenian, Bajocian and Bathonian strata possess relatively distinct sporomorph and palynofacies assemblages, which potentially reflect a dynamic history regarding the nature of parent vegetation. Specifically, Aalenian palynofloras are composed of a heterogeneous mixture of conifers, ferns, simple monosulcate pollen producers, sphenophytes and Caytoniales; Bajocian palynofloras are codominated by conifers and ferns; and Bathonian palynofloras are highly rich and contain assemblages of abundant ferns, conifers, lycophytes, pteridosperms/conifers and Caytoniales. Individual‐ and sample‐based rarefaction demonstrates that Bathonian samples are richer than Aalenian and Bajocian samples. Temporal variations in assemblages are a result of long‐term depositional and possible climatic fluctuations through the Middle Jurassic. Ordinations of sporomorph data using non‐metric multidimensional scaling (NMDS) demonstrate that short‐term variations between samples are largely governed by taphonomic biases as a result of slight changes in depositional processes, which give rise to highly variable catchment areas that supply deposits with sporomorphs. Long‐term compositional changes are apparent in sporomorph assemblages regardless of lithology/local depositional environments, suggesting that long‐term variations are more substantial than short‐term variations and potentially include genuine regional temporal changes in parent vegetation. Relating sporomorph assemblages with their respective depositional environments and relative catchment area sizes using lithological and palynofacies information suggests that the basin interior was occupied by mostly low‐standing species and extrabasinal vegetation was dominated by coniferous taxa. Comparisons of the dispersed sporomorph and plant megafossil records indicate that both fossil assemblages reflect different aspects of the palaeoflora due to a multitude of taphonomic and ecological biases. Such biases include variation in sporomorph production levels, depositional environment and differential sporomorph and parent plant durability.

Pollen morphology of some Brazilian Xyris Gronov. ex L. (Xyridaceae) species

Although the pollen morphology of Xyridaceae shows standard patterns that distinguish five genera, specific data of each genus are scarce or incompletely known. The pollen morphology of 17 Brazilian species of Xyris (Nematopus Section) based upon 47 specimens from Goias and Minas Gerais States, Brazil, is presented. Micrographs of pollen grain structures were obtained using light and scanning electron microscopy. Pollen grains are characterized as monads, medium to large sized, ellipsoidal in polar view, flattened/convex in equatorial view and monosulcates. The sulci are pontoperculate and covered with an insulae type membrane. The sexine presents either a microreticulum or rugulae with perforations, and is thicker than the nexine. Although Xyris is a stenopalynous genus, characterized by monosulcate pollen grains, two groups of species were recognized based upon pollen size as well as pollen wall ornamentation features. Therefore, pollen data are of taxonomic value and useful to clarify the delimitation of the studied species.

Comparative pollen morphology and viability among endangered species of Butia (Arecaceae) and its implications for species delimitation and conservation

The present study reports the results of pollen analyses on four species of Butia (Arecaceae), Butia odorata, B. yatay, B. paraguayensis and B. lallemantii. Pollen grains were described using light microscopy (LM) and scanning electron microscopy (SEM), and pollen viability was determined by the fluorochromatic reaction (FCR) test. All species of Butia studied produce monosulcate pollen grains with a tectate perforate exine. Additionally, B. odorata and B. paraguayensis produce two pollen grain types, mono- and also trichotomosulcate, which has been considered a derived state of the character. Regarding pollen grain size and shape, there are significant differences in long and short axis lengths, and their ratio. Despite serious regeneration problems which jeopardise population survival in the short-term future, results showed that pollen viability of all species of Butia analysed was high enough to ensure good pollination. Therefore, pollen viability is not the limiting factor for population continuity. This is the first study dealing both with pollen morphology and assessment of pollen viability with the aim of species delimitation within this genus. Additionally, this is the first study providing new information regarding the status of the current Butia populations of southern South America from a palynological point of view.

The Middle Jurassic palynology of the Daohugou area, Inner Mongolia, China, and its implications for palaeobiology and palaeogeography

Although abundant palaeontological discoveries have been documented in the Daohugou area in Chifeng City, Inner Mongolia, China, no record of the palynoflora has been reported previously. We collected palynological samples from the same level as megafossil plants, and conducted a detailed taxonomic analysis of the pollen and spores in order to augment the megafossil record, to extend documentation of the Middle Jurassic palynoflora, and to examine implications for palaeogeography, palaeoecology and palaeoclimate in north China during the Jurassic. Forty-four genera and 87 species of palynomorphs were identified. Pollen of gymnosperms dominates numerically, followed by spores of pteridophytes. Most taxa, including bisaccate pollen of conifers, monosulcate pollen of Cycadales, Bennettitales or Ginkgoales, along with Cyathidites, Deltoidospora, Granulatisporites, Osmundacidites and Classopollis, are common elements known elsewhere during the Jurassic. Based on comparisons with similar palyno-assemblages in the Jurassic of China, the age of the Daohugou locality is interpreted to be late Middle Jurassic. According to the palaeobotanical and palaeopalynological information, the Daohugou flora is attributed to the warm-temperate to medium temperate zone with seasonal change. By studying the ecological and climatic preferences of the main plant groups, five types of palaeolandscape in the Jurassic of Daohugou are proposed: (1) mesic upland (Pinaceae, Podocarpaceae, Czekanowskiales and Bennettitales), (2) mesic lowland (Pinaceae, Podocarpaceae, Ginkgoales, Czekanowskiales and Cycadales, together with some hygrophilous bryophytes, lycophytes and ferns), (3) dry upland (Czekanowskiales), (4) dry lowland (Czekanowskiales and Cheirolepidiaceae) and (5) waterside (plants growing along streams or near lakes, including bryophytes, lycophytes, ferns and probably some pteridosperms). According to the plant assemblage, the Daohugou flora corresponds to that of the Middle Jurassic Northern Floristic Province of China, which experienced a transition from a humid, warm climate to a hotter climate with seasonal drought.

Permian palynostratigraphy of the Claromecó Basin, Argentina

The first palynozonation for Permian strata of the Claromecó Basin (Argentina) is formally proposed, based on palynological assemblages recovered from the UTAL.CMM1 La Estrella.x-1 and UTAL.CMM1 Cruz de Sur.x-1 boreholes, drilled on the Argentinian Continental Platform and correlation with established zones from neighbouring basins. Fifty-five samples were analyzed and 131 species identified from two biozones. The lower Converrucosisporites confluens–Vittatina vittifera (CV) Zone occurs in the Piedra Azul and Bonete formations of both boreholes. This zone can be assigned a Cisuralian–Guadalupian age. The upper Tornopollenites toreutos–Reduviasporonites chalastus (TC) Zone registered in the Tunas Formation can be assigned a Guadalupian–Lopingian age. The CV Zone is dominated by diverse non-taeniate bisaccate, plicate and taeniate pollen. Monosaccate and monosulcate pollen, algae and acritarchs are poorly represented in both biozones. The composition of the TC Zone is broadly similar to the CV Zone, but bisaccate pollen grains are markedly more diverse and abundant in the former.

Pollen cones and associated leaves from the Lower Cretaceous of China and a re-evaluation of Mesozoic male cycad cones

Male cones of Ixostrobus hailarensis from Lower Cretaceous strata of the Hailar region of north-east China were re-examined for features of their cuticle and in situ pollen. The cones are loosely aggregated and possess helically arranged peltate microsporophylls containing resin bodies. Microsporophyll cuticle is thick, papillate and has elliptical stomata with 6–9 subsidiary and ∼10 encircling cells. Adaxial sporangia contain monosulcate pollen assignable to the dispersed taxon Cycadopites minimus. Both the cuticle and pollen are distinct from Ixostrobus but are consistent with the cycad genera Androstrobus, Aegianthus, Loricanthus and the putative angiosperm Solaranthus. Reanalysis of the type species of Androstrobus, A. zamioides, provides new information on its structure and allows an accurate delimitation of the genus and improved comparison with other genera. A new genus, Schimperstrobus, is erected for species now excluded from Androstrobus. Comparisons indicate that Solaranthus represents a male cycad cone and that Aegianthus, Loricanthus and Solaranthus are synonyms; Aegianthus has nomenclatural priority. We emend the combined generic and specific diagnoses for Aegianthus sibiricus to allow additional species to be placed in the genus, and erect the new combinations Aegianthus resinifera for specimens previously assigned to Loricanthus, and Aegianthus daohugouensis for specimens previously placed within Solaranthus. The Hailar cone conforms to the generic circumscription of Aegianthus and represents a new species that we name A. hailarensis comb. nov. Androstrobus phialophora also conforms with Aegianthus and is transferred to Aegianthus phialophora comb. nov. Co-occurring with A. hailarensis are cuticles of the ginkgophyte leaf Sphenobaiera longifolia that are similar to microsporophyll cuticles of A. hailarensis. However, we discount that they belong to a single plant species and conclude that the cuticles of some Mesozoic ginkgoalean and cycadalean taxa may be virtually indistinguishable. We consider that Aegianthus was widespread across China, Mongolia and southern Russia during the Upper Jurassic to Lower Cretaceous.