Megaspores

Quantitative plant assemblage data from coal balls, miospores, megaspores, and compression floras from the Calhoun coal bed (Missotirian) of the Illinois Basin (USA) are used to interpret spatial and temporal changes in plant commtinities in the paleo-peat swamp. Coal-ball and miospore floras from the Calhoun coal bed are dominated strongly by tree ferns, and pteridosperms and sigillarian lycopsids are subdominant, depending on geographic location within the coal bed. Although the overall composition of Calhotin peat-swamp assemblages is consistent both temporally and spatially, site-to-site differences and short-term shifts in species dominance indicate local topographic and hydrologic control on species composition within the broader context of the swamp. Statistical comparison of the Calhoun miospore assemblages with those from other Late Pennsylvanian coal beds suggests that the same basic species pool was represented in each peat-swamp landscape and that the relative patterns of dominance and diversity were persistent from site to site. Therefore, it appears that the relative patterns of proportional dominance stayed roughly the same from one coal bed to the next during Late Pennsylvanian glacially-driven climatic oscillations. Published by Elsevier B.V.

Fossil assemblages are described from the Tyers River Subgroup (late Berriasian to Hauterivian), Gippsland Basin, Victoria. The assemblages include plant macrofossils referable to 33 form-species including five new species (Isoetites abundans Tosolini & McLoughlin, Coniopteris victoriensis Nagalingum & McLoughlin, Otozamites douglasii Drinnan, Brachyphyllum tyersensis Tosolini & Nagalingum, Otwayia hermata Tosolini & McLoughlin) and three new combinations [Medwellia lacerata (Douglas) Nagalingum & McLoughlin, Rintoulia variabilis (Douglas) McLoughlin & Nagalingum, Pachydermophyllum austropapillosum (Douglas 1969) McLoughlin & Nagalingum]. Macrofossil assemblages include representatives of the Hepaticales, Isoetales, Equisetales, Filicopsida, seed-ferns, Coniferales and unionid bivalves. Co-preserved mesofossil suites include dispersed cuticle fragments, seed coats, seed megaspore membranes, microspore clusters, fern leptosporangia, charcoalified wood, resin blebs, epiphyllous fungal shields, clitellate annelid cocoons, insect exoskeleton fragments and coprolites. Sixteen lycophytic megaspore taxa were identified from the succession including six newly described species (Erlansonisporites confertus Tosolini, Favososporites brevis Tosolini, Hughesisporites australis Tosolini, Paxillitriletes rintoulensis Tosolini, Striatriletes imperfectus Tosolini, Trikonia locmaniensis Tosolini). These represent the first Neocomian megaspores formally described from Australia and their diversity and abundance indicates that lycophytes represented a significant component of the Early Cretaceous vegetation. The Tyers River Subgroup shares some taxa with the well-studied Koonwarra Fossil Bed (Aptian) flora of the Gippsland Basin but lacks several key elements (Ginkgoales, angiosperms and large-leafed araucarian conifers) and is more closely comparable to Jurassic floras of eastern Australia in its strong representation of bennettitalean, pentoxylalean and other seed-fern remains. The Tyers River Subgroup flora differs from coeval northwestern Australian floras by possession of smaller-leafed bennettites, Komlopteris and Pachydermophyllum species and by the lack of dipteridacean and gleicheniacean/lophosoriacean fern macrofossils. This intra-Australian provincialism is interpreted to be largely a function of palaeolatitude-induced climatic differences. Six major biofacies (one divisible into four sub-facies) are recognized in the Tyers River Subgroup and are attributable to three broad environmental settings within fluvial depositional tracts. Channel deposits host principally detrital plant remains derived from a broad range of riparian, upland, and reworked floodbasin communities. Silty floodbasin deposits typically host a mixture of pteridosperm-, fern- and lycophyte-dominated assemblages derived from a mosaic of herb-, shrub- and small tree-dominated communities developed mainly in perennially or seasonally wet environments. Better-drained, intervening levee, crevasse splay and neighbouring upland environments are interpreted to have hosted a conifer-dominated flora contributing to conifer-, root/rhizome-, megaspore-and clitellate-rich fossil associations. The floristic diversity, foliar morphology of selected species, strong representation of deciduous taxa and sedimentological data collectively suggest that seasonally cold conditions prevailed during the Neocomian-Aptian compared to the Albian in southeastern Australia.

The Permian-Triassic boundary within the Amery Group of the Lambert Graben is placed at the contact between the Bainmedart Coal Measures and overlying Flagstone Bench Formation, based on the first regular Occurrence of Lunatisporites pellucidus and the first appearance of Aratrisporites and Lepidopteris species. The Permian-Triassic boundary is marked by the extinction of glossopterid and cordaitalean gymnosperms, and by the disappearance or extreme decline of a range of gymnospermous and pteridophytic palynomorph groups. Earliest Triassic macrofloras and palynofloras of the Flagstone Bench Formation are dominated by peltasperms and lycophytes; corystosperms, conifers, and ferns become increasingly common elements of assemblages through the Lower Triassic part of the formation and dominate floras of the Upper Triassic strata. The sedimentary transition across this boundary is conformable but marked by a termination of coal deposits; overlying lowermost Triassic sediments contain only carbonaceous siltstones. Typical redbed facies are not developed until at least 100 m above the base of the Flagstone Bench Formation, in strata containing ?Middle Triassic palynofloras. Across Gondwana the diachronous disappearance of coal deposits and appearance of red-beds is suggestive of a response to shifting climatic belts, resulting in progressively drier seasonal conditions at successively higher palaeolatitudes during the Late Permian to Middle Triassic. The abrupt and approximately synchronous replacement of plant groups at the Permian-Triassic boundary suggests that factors independent of, or additional to, climate change were responsible for the turnover in terrestrial floras.

As part of an on-going multidisciplinary investigation of the Bristol Coalfield we present a detailed account of assemblages of megaspores and large pollen grains from the mid-Bolsovian to late Asturian Warwickshire Group (Winterbourne, Pennant Sandstone and Grovesend formations). The megaspore assemblages show certain similarities to those from the well documented, and partly coeval, sequence in the nearby Forest of Dean Coalfield. However, the Bristol Coalfield megaspore assemblages are generally less diverse. We consider the palaeoecological implications of the megaspore assemblages and conclude that differing depositional settings had different vegetational successions (including differences in the composition and diversity of megaspore-producing plants). A consideration of megaspore biostratigraphy suggests that the uppermost Pennant Sandstone Formation may be of early Asturian age, suggesting that the postulated gap between the Pennant Sandstone Formation and overlying Grovesend Formation is smaller than previously suggested. We also report the first European occurrence of the large enigmatic pteridosperm pollen grain Parasporites maccabei.

The Permian-Triassic boundary within the Amery Group of the Lambert Graben is placed at the contact between the Bainmedart Coal Measures and overlying Flagstone Bench Formation, based on the first regular Occurrence of Lunatisporites pellucidus and the first appearance of Aratrisporites and Lepidopteris species. The Permian-Triassic boundary is marked by the extinction of glossopterid and cordaitalean gymnosperms, and by the disappearance or extreme decline of a range of gymnospermous and pteridophytic palynomorph groups. Earliest Triassic macrofloras and palynofloras of the Flagstone Bench Formation are dominated by peltasperms and lycophytes; corystosperms, conifers, and ferns become increasingly common elements of assemblages through the Lower Triassic part of the formation and dominate floras of the Upper Triassic strata. The sedimentary transition across this boundary is conformable but marked by a termination of coal deposits; overlying lowermost Triassic sediments contain only carbonaceous siltstones. Typical redbed facies are not developed until at least 100 m above the base of the Flagstone Bench Formation, in strata containing ?Middle Triassic palynofloras. Across Gondwana the diachronous disappearance of coal deposits and appearance of red-beds is suggestive of a response to shifting climatic belts, resulting in progressively drier seasonal conditions at successively higher palaeolatitudes during the Late Permian to Middle Triassic. The abrupt and approximately synchronous replacement of plant groups at the Permian-Triassic boundary suggests that factors independent of, or additional to, climate change were responsible for the turnover in terrestrial floras.

the morphology and structure of megaspores assigned to Lagenoisporites magnus from the toregua Formation, retama Group, mid-upper tournaisian of Bolivia were studied. the analysis was performed with light, fluorescence and scanning electron microscopy. Megaspores were laterally compressed and presented a spherical body with a proximal gula, of the hologula type. Gula had verrucae ornamentation and the spore body presented complex processes consisting of a bulbous base and an internally partitioned projection with sharp apex. In addition to this main ornamentation, perforations were present throughout the spore surface. Megaspores showed well marked curvaturae perfectae due to the abrupt transition existing between the gula ornamentation and the spore body processes. these megaspores were assigned to heterosporous arborescent lycopsids of the Lepidocarpaceae family, as in section view, exospore structure presented a three-dimensional network of fused elements. Likewise, due to a similarity found between sporoderm and Isoetes L. structure, it is evident that megaspores structure has remained intact inside the heterosporous lycopsids. therefore; the L. magnus structure not only would confirm its affinity with the Lycophyta fossils but also with the living ones.

This study describes the megaspore assemblages from the Ryabinsk Member of the Vokhma Formation of the Moscow Syneclise. The genus Otynisporites is emended, three new species, Maexisporites meditectatus, M. rugulaeferus and Otynisporites maculosus, are erected, and one new combination, Maexisporites grosstriletus, is proposed. Megaspore descriptions relate the gross morphology and fine structure of the exine surface of thirteen taxa. From the appearance of the exine surface and ornamentation processes, it appears that some forms currently included in certain genera according to their morphological features do not belong to them. The assemblage from Sholga is evidently of low diversity at the generic level, possibly reflecting the end-Permian biotic crisis. The composition of the megaspore assemblages indicates their Induan age.

lN Nlo" rotatos 01' rll/~'I'l\Nt\NÁ IJ/\SIN, Sil O I'l'lUI.o STi\ lE, IJNA Z/ L Th ix rcsc urch pres em lhe rcsults 0 1' dc tailc d sy stcu uuic stud y ubo ur the mcg usporc s found in thc scdim cnt ary rocks of Itararé S ubg roup (U ppcr C urboniferuus) toca tcd ut thc north c astcrn ponion of Paran á Haxin (São Paulo State), Br azil. The st ud ied outcmp was dcpositcd by subaquosos fans loc ntcd at lhe lo wc r portion of ltamré S ubgroup with glacial influencc during the Westaphlian lim es. Pour spccics o f mcgaspores are here dcscribed and illustratcd: SlIlJfagcllimla brosilicnsís, S. .\' illllll(ll. Tritcitvs tenuis and Caknnospora sp. Th c spccies o f thc genusSublagcllin da are dominam. Are hcre discussed lhe rc iationship prc sents nmon g othcr species of mega spores 100. and tem poral und spac ia l distribution o f that four spccics for Paraná n us!n and Go ndwana.

Steemans et al., Libyan megaspores page 2 A restudy of Devonian palynological assemblages of samples from the A1-69 borehole, drilled in the Ghadamis Basin, western Libya, North Africa has led to the discovery of numerous well-preserved megaspores amongst abundant miospores, rare acritarchs and rare chitinozoans. Thirteen samples from base to top, 1496 ft (456 m) up to 965 ft (294 m), contain the richest Devonian megaspore assemblages from northwestern Gondwana. The section is dated by a rich diverse miospore assemblage indicating the presence of the upper part of the AD pre-Lem Biozone up to the lower part of the TCo Oppel Zone, ranging from a latest Eifelian or earliest Givetian age up to a latest Givetian or an earliest Frasnian age. Sixteen megaspore taxa have been identified. Among them, two new species (Biharisporites lugardonii and Lagenicula milleri) and four new varieties (Corystisporites acutispinosus var. acutispinosus and var. bullatus, Heliotriletes longispinosus var. longispinosus and var.

Deux nouvelles espèces de mégaspores, Biharisporites jubahensis et Verrucisporites yabrinensis, découvertes dans la partie méridionale du centre de l'Arabie Saoudite sont décrites dans la Formation Jubah, d'âge Dévonien moyen. D'après la biostratigraphie des ...

Recent Arctic drilling has revealed that the freshwater surface-floating heterosporous fern Azolla arctica Collinson et al. (Azollaceae, Salviniales) bloomed and reproduced in the Arctic Ocean on a massive scale during the early Middle Eocene. These blooms have been suggested to have been capable of significant drawdown of atmospheric CO 2 paving the way to Cenozoic climatic cooling. Sites of similar age across the Arctic and Nordic Seas also contain Azolla fossils suggestive of an area much larger than the Arctic Ocean being affected by Azolla blooms, as far south as Denmark. Here we investigate the Danish occurrences known from the Lillebaelt Clay Formation, transitional Ypresian/Lutetian in age (latest Early Eocene to earliest Middle Eocene). The Lillebaelt Clay is a marine deposit rich in diverse organic-walled dinoflagellate cysts yet conspicuously characterized by abundant co-occurring and interconnected fully mature Azolla megaspores and microspore massulae. Perhaps surprisingly, we find that multiple morphological and ultrastructural characters distinguish the Danish Azolla species from Azolla arctica and it is here described as Azolla jutlandica sp. nov. Therefore, contrary to expectations given the overlapping age of these assemblages, it appears that not a single Azolla species has spread from the Arctic to the Southern North Sea either through freshwater spills from the Arctic Ocean or as a result of rapid spread due to highly invasive biology. Apparently Northern Hemisphere middle and high latitude conditions near the termination of a period known as the Early Eocene Climatic Optimum (EECO) were suitable for proliferation of two different Azolla species, one in the Arctic Ocean and one in the southern North Sea.

1 Laboratoire de Paleobotanique, Paleopalynologie et Micropaleontologie, Universite de Liege, Allee du 6 aout, B18, Sart-Tilman, 4000 Liege (Belgium) [email protected] 2 Laboratoire de Paleobotanique, Paleopalynologie et Micropaleontologie, Universite de Liege, Allee du 6 aout, B18, Sart-Tilman, 4000 Liege (Belgium) [email protected] 3 NFSR Research associate; Laboratoire de Paleobotanique, Paleopalynologie et Micropaleontologie, Universite de Liege, Allee du 6 aout, B18, Sart-Tilman, 4000 Liege (Belgium) [email protected] 4 Laboratoire de Paleobotanique, Paleopalynologie et Micropaleontologie, Universite de Liege, Allee du 6 aout, B18, Sart-Tilman, 4000 Liege (Belgium) [email protected] 5 Laboratoire de Paleobotanique, Paleopalynologie et Micropaleontologie, Universite de Liege, Allee du 6 aout, B18, Sart-Tilman, 4000 Liege (Belgium) [email protected] 6 Laboratoire de Paleobotanique, Paleopalynologie et Micropaleontologie, Universite de Liege, Allee du ...

Transactions of the Royal Society of Edinburgh: Eanh Sciences, 76, 13-20, 1985 Plants from the Dinantian of Foulden, Berwickshire, Scotland Andrew C. Scott and Brigitte Meyer-Berthaud ABSTRACT: Anatomically preserved plants are recorded from calcareous nodules and ...

Transactions of the Royal Society of Edinburgh: Eanh Sciences, 76, 13-20, 1985 Plants from the Dinantian of Foulden, Berwickshire, Scotland Andrew C. Scott and Brigitte Meyer-Berthaud ABSTRACT: Anatomically preserved plants are recorded from calcareous nodules and ...

The morphology and ultrastructure of megaspores, microspores, and massulae of Salvinia Séguier 1785 species from Argentina, Bolivia, southern Brazil, Chile, Paraguay, and Uruguay have been analyzed. The analyses were performed using light microscopy, stereo microscopy, scanning electron microscopy, and transmission electron microscopy. The taxa studied were Salvinia auriculata Aublet 1775, Salvinia biloba Raddi 1825, and Salvinia minima Baker 1886. The spores of Salvinia biloba are described and illustrated here for the first time. The spores of Salvinia adnata Desvaux 1827were not described here because all the specimens analyzed had megasporangia and microsporangia which had not developed, or were aborted. The megaspores in all the species analyzed are trilete, 224-402 µm in polar diameter and 179-378 µm in equatorial diameter, with a circular outline, an irregular margin in polar view, and are ovoid in equatorial view. The surface is ridged and perforated and the sporoderm in cross section comprises a compact, two-layered exospore and a thick lacunose epispore which is projected proximally. The apertural area has unique characteristics in each species. The microspores are enclosed in spheroidal to elliptical massulae 145-240 µm in diameter. The individual microspores are trilete, rugulate, 15-36 µm in diameter, and spheroidal. In cross section, the exospore is two-layered. Both types of spores produced by the species analyzed exhibit little interspecific and intraspecific variability. Differences in general shape and proximal characteristics were found in megaspores at the species level. According to these, and previous, results Salvinia is a genus with stable palynological characteristics, all of them related to its adaptation to the aquatic environment.