Review of Palaeobotany and Palynology

Published by Elsevier
Online ISSN: 0034-6667
Publications
Article
A pollen record from Timbio, located at an elevation of 1750m on the high plain of Popayán (2 degrees 24'N, 76 degrees 36'W) is presented. This forms the basis for reconstructing the vegetation and climate history for the periods from 27000 to 9200 radiocarbon years before the present (14Cyr BP) and 2100 14Cyr BP to sub-recent. The 5m sediment core has time control based on seven AMS radiocarbon dates. Four pollen assemblage zones (TIM-1 to TIM-4) are recognized. During the period of 27200 to 26000 14Cyr BP, an Andean forest was near the site. The vegetation consisted of forest and open herb-rich vegetation, climatic conditions were moist and temperatures some 6 degrees C lower than compared to those of today. During the period of 26000 to 16000 14Cyr BP forest was less open. The observed succession from a Podocarpus-Weinmannia dominated forest to a Hedyosmum dominated forest, and finally to a forest with Ilex, Myrica and ferns indicates a progressive decrease of temperature during this period, with a maximum temperature depression of ca. 5-7.5 degrees C compared to present-day conditions. During the period of 16000 to 9200 14Cyr BP, temperature decrease is estimated at ca. 7.5 degrees C and the climate was the driest. During the period of 2100 to 600 14C2600m altitude (ca. 8 degrees C) and those at sea-level (2.5-6 degrees C) and supports the observation that glacial lapse rates were higher than in modern times.
 
Article
A floral change occurring in northern South America at the Paleocene/Eocene boundary is analysed using palynological data. The sequence studied is an outcrop from the Venezuelan Maracaibo basin, deposited in shallow marine to coastal environments without apparent stratigraphic breaks. Significant pollen and spore counts from 237 samples were studied stratigraphically and statistically in order to compare Paleocene and Eocene palaeofloras and palaeoecological trends. The Late Paleocene/Early Eocene transition is the boundary between two floras which differ both qualitatively and quantitatively. However, the change is not sudden but stepped and gradual. Paleocene taxa seem to be of pantropical distribution, whereas Eocene assemblages are more restricted to the Neotropics. The global warming well documented elsewhere is proposed as the major cause for these changes. Trends in sporomorph diversity in this record appear to track changes in temperature documented in isotopic records from temperate regions. The extinct parent plant of Echitriporites trianguliformis is tentatively proposed to be intolerant to high temperatures, because of its absence during the Early Eocene warm phase. Palaeoecologically, although marsh and back-mangrove swamps dominated both Late Paleocene and Early Eocene assemblages, their taxonomic compositions were different, especially in the inland marsh forests. Mangrove components are scarce or absent through the whole sequence studied, suggesting the absence of these communities during the time-interval analysed. A palaeoecological subdivision into assemblage zones was not possible; instead, a recurrent pattern suggesting palynological cycles was observed. However, palynocycles could not be studied in detail due to the lack of knowledge of botanical affinities for many of the taxa involved and the apparent absence of mangrove assemblages.
 
Article
A total of 23 pollen diagrams [stored in the Alpine Palynological Data-Base (ALPADABA), Geobotanical Institute, Bern] cover the last 100 to over 1000 years. The sites include 15 lakes, seven mires, and one soil profile distributed in the Jura Mts (three sites), Swiss Plateau (two sites), northern Pre-Alps and Alps (six sites), central Alps (five sites), southern Alps (three sites), and southern Pre-Alps (four sites) in the western and southern part of Switzerland or just outside the national borders. The pollen diagrams have both a high taxonomic resolution and a high temporal resolution, with sampling distances of 0.5–3 cm, equivalent to 1 to 11 years for the last 100 years and 8 to 130 years for earlier periods.
 
Article
Charcoal analysis of six shell mounds showed that no major changes of the mainland vegetation ecosystem have taken place along the southeastern Brazilian coast (22°53′–22°57′S, 42°03′–42°33′W) from 5500 to 1400 ¹⁴C yr BP. These shell mounds have been occupied by sedentary fisher–gatherer–hunters. Charcoal fragments retrieved from vertical profiles in the archaeological sites were examined; taxonomic determinations were based on a reference collection of charred woods and a program for computer-aided identification. Charcoal assemblages of all the studied sites present taxa from various restinga vegetation types, mangroves, xeromorphic coastal forest, and inland Atlantic Forest. The restinga ecosystem, characteristic of the Brazilian coast, is associated with sandy beach ridges; the restinga forest was much more abundant during the studied period than nowadays. The charcoal assemblages represent mainly the local vegetation; a regional reconstruction depends on the study of numerous sites. In the Cabo Frio region, open restinga taxa are more abundant in the Sambaqui do Forte, while forest elements are more important in the Sambaquis Salinas Peroano and Boca da Barra. The sites studied in the Arraial do Cabo (Sambaqui da Ponta da Cabeça) and in the Saquarema regions (Sambaquis da Pontinha and da Beirada) show that open restinga formations were locally predominant. A comparison of multivariate analysis applied to both charcoal assemblages and to phytosociological data of the extant vegetation showed a good correspondence between the charcoal spectra and the present vegetation. The high taxonomic diversity of archaeological charcoal samples and numerous fragments showing traces of decay before charring suggests that aleatory gathering of dead wood constituted the main source of firewood for fisher–gatherer–hunters populations. Condalia sp. was probably selected for cultural reasons.
 
Article
Morphological variations are examined in the dinoflagellate cysts Spiniferites spp., Lingulodinium polyedrum and Protoceratium reticulatum (=Operculodinium centrocarpum) from a core taken in the Bjørnsholm Bay, the Limfjord, Denmark. The fjord has a history of changing salinity, and unusual cyst morphotypes are found in the greatest numbers during periods of inferred low salinity. Variation occurs primarily in cyst process morphology, and the aberrant morphotypes have processes that are shorter, thicker and/or more membranous. The different morphotypes are described and compared with other varieties and forms of the three taxa and to other closely related taxa.
 
Article
The island of Rügen (NE Germany), situated close to the Trans-European Suture Zone (TESZ), in the southern Baltic Sea is underlain by sedimentary rocks of an Early Palaeozoic age, known only from boreholes. The wells, Rügen 5/66 and Binz 1/73, were investigated for their chitinozoan assemblages to improve the earlier biostratigraphic dating (graptolites and acritarchs) and to facilitate comparisons with other chitinozoan assemblages on both sides of the TESZ. In the lower part of the Rügen 5/66 core (3794.7-3615.8m), Lagenochitina destombesi Elaouad-Debbaj is indicative of an early late Tremadoc age. In the upper part of the same well (3287.3-1709.7m), the observed chitinozoan taxa suggest an age spanning the early Llanvirn to the Caradoc. The entire sampled interval of the Binz 1/73 core (5217.6-5041.8m) is interpreted as belonging to the Siphonochitina formosa Biozone (early-early late Abereiddian, corresponding to the early Llanvirn). The chitinozoan data corroborate the earlier suggested biostratigraphic ages, based on acritarchs and graptolites. The chitinozoans from the Binz 1/73 well point to a high latitude provenance of the investigated host sediments at time of deposition.
 
Article
This is the third paper of an extensive study of pollen morphology and exine structure of Acalyphoideae (Euphorbiaceae) following the most recent system of Webster. Pollen from 120 collections representing 96 species and 30 genera is described and illustrated with light microscopy, scanning and transmission electron microscopy. These taxa are from tribes Epiprineae, Adelieae, Alchorneae, and Acalypheae pro parte. Pollen of eight genera, Epiprinus, Symphyllia, Adenochlaena, Cleidiocarpon, Koilodepas, Cladogynos, Cephalocrotonopsis and Cephalocroton, of the nine assigned to Epiprinae share 3-colporate apertures, microreticulate, punctate or deeply punctate tecta, well developed or prominent columellae (Koilodepas excepted) and thin foot layers; pollen of the ninth genus, Cephalomappa, has porelike colpi, a coarsely reticulate exine, irregular columellae and an irregular foot layer. Of the five genera assigned to Adelieae, pollen of Adelia, Lasiocroton and Leucocroton is similar: 3-colp(oroid)ate with stratified opercula, crotonoid tecta and thin foot layers; grains of Enriquebeltrania and Crotonogynopsis lack opercula and the latter has a distinctive infratectum of poorly differentiated columellae. All genera examined of tribe Alchorneae, seven of the nine, have exines with unstratified opercula and elongated columellae near the endoaperture. Exines of subtribe Alchorneinae (Orfilea, Alchornea, Coelebogyne, Aparisthmium, Bocquillonia) have complex infratecta of poorly differentiated columellae, whereas pollen of Conceveiba and Gavarretia, the two genera examined of the three assigned to subtribe Conceveibinae, has a single layer of short columellae and almost identical tectal morphology. In the large tribe Acalypheae, pollen of the first six of the 11 subtribes was examined. Pollen of Ricinus (Ricininae) and Adriana (Adrianinae) share indistinguishable exine structures and tecta. Pollen of Mercurialis and Leidesia of subtribe Mercurialinae and pollen of Dysopsis of subtribe Dysopsidinae are almost identical: finely reticulate tecta, very thin apertural endexines, elongate columellae, and channeled/perforate foot layers. All three genera of subtribe Cleidiinae have grains that are 3-colporate and have complete tecta; pollen of Wetria has a tectum morphology very similar to that of Ricinus and Adriana; pollen of Cleidion is 3-brevicolporate with microrugulose or punctate tecta, and has threadlike non-apertural endexines and foot layers, and thick tecta; exines of Sampantaea have an endexine throughout the grain, thin foot layers, very short columellae and a thick continuous tectum. Pollen of Macaranga of subtribe Macaranginae is small, 3-colporate with poorly defined endoapertures, and an exine structure characterized by thin foot layers, short columellae, and thick tecta. Pollen data support: the concept of the subtribe Epiprininae, but indicate that subtribe Cephalomappinae (Cephalomappa) is not related and should be considered for separate tribal status; a close relationship among Adelia, Lasiocroton and Leucocroton, but not with the two remaining members of Adelieae, Enriquebeltrania and Crotonogynopsis, which do not appear to be closely related to each other; the present concept of Alchorneae and subtribes Alchorneinae and Conceveibinae. Within the genera examined of the first six subtribes of Acalypheae, the pollen data: support a close relationship between the monogeneric subtribes Ricininae and Adrianinae; indicate a close relationship between subtribes Mercurialinae (Mercurialis, Leidesia) and Dysopsidinae (Dysopsis); suggest that Wetria is not closely related to Cleidion or Sampantaea (Cleidiinae); tentatively support the concept of Macaranginae as comprising only Macaranga.
 
Article
The Late Jurassic to Early Cretaceous genus Tritaenia Maegdefrau et Rudolf 1969 is problematic because of: (1) missing authentic material of its type species, T. linkii (Roemer 1839) Maegdefrau et Rudolf; and (2) Watson and Harrison's (1998) synonymization of T. linkii with Pseudotorellia heterophylla Watson. This paper: (1) rectifies the status of T. linkii on the basis of newly recovered specimens carrying the original author's authentication; and (2) gives the basis for rejecting Watson and Harrison's claim that T. linkii and T. crassa (Seward) Bose et Manum 1991 represent linear leaves of the heterophyllous taxon Pseudotorellia heterophylla. The three species of Tritaenia known to date (T. crassa, T. linkii, T. scotica) are reviewed, and the genus is compared with other Mesozoic so-called 'Sciadopitys-like' hypostomatic leaves with a median stomatal zone, many of which occur in mass accumulations such as T. linkii. Deciduousness is indicated for T. linkii and T. crassa by their occurrence in mass accumulations and the possession of well-developed abscission scars. Known mass accumulations of fossil foliage are reviewed and their implications for palaeoenvironmental interpretations discussed.
 
Article
CHITINOS is a microfossil image and data acquisition system developed to support palynologists from field work to report production. The system is intended for chitinozoans, but it can also accommodate other fossil groups. Thanks to its client-server architecture, the system can be accessed by multiple users. The database can be filled with data acquired during palynological work or taken from the literature. The system allows for the easy input, update, management, analysis and retrieval of paleontological data to enable the paleontologist to elucidate paleogeographic patterns, changes in biodiversity and taxonomic differentiations. Query and plot interfaces are intended for report production. The system was designed as the basis of a knowledge expert system by providing a new perspective in the interpretation of interrelated data.
 
Article
A pelagic sedimentary succession, virtually complete from the Upper Hauterivian to the Upper Aptian and unconformably overlain by the Middle-Upper Albian p.p., was continuously cored in the Belluno Basin (southern Alps, NE Italy) as part of the APTICORE Program. APTICORE at Cismon Valley penetrated 131.8m of limestones, marls and black shales, with 100% recovery of good quality cored material.One hundred and forty-six samples recovered from the marl and shale beds of the Cismon core were processed and analyzed for palynomorphs. Most of them yielded relatively rich and fairly well preserved assemblages of marine and terrestrially-derived palynomorphs.The results of a qualitative study of dinoflagellate cysts and acritarchs are presented and discussed. The distributions of 150 taxa are tabulated against the chronostratigraphy independently established on the basis of original litho-, bio-, chemo-, magnetostratigraphic investigations and of correlations with extensively studied sections outcropping in the vicinity of the Cismon drill site.The acritarch Pinocchiodinium erbae gen. et sp. nov. is described. Due to its distinctive morphology and extremely constant occurrence also in the black shales of the Selli Level, it is proposed as a marker species for the Aptian sediments of the Tethys.The dinoflagellate cysts Kallosphaeridium dolomiticum sp. nov. and Nexosispinum hesperus brevispinosum subsp. nov. are described from the Upper Hauterivian. Additional taxonomic remarks are made about other dinoflagellate cyst species, including the emendations of Tanyosphaeridium magneticum Davies 1983 and Bourkidinium granulatum Morgan 1975.The biostratigraphic value of selected taxa is discussed and compared with data known both from the Tethyan and Boreal realms. In particular, the extinction of Bourkidinium granulatum emend. is proposed as the best dinoflagellate cyst event for the delimitation of the Hauterivian-Barremian boundary in the Northern Hemisphere. The first appearance datums of Prolixosphaeridium parvispinum and Odontochitina operculata, and the slightly younger last appearance datum of Nexosispinum vetusculum are confirmed as useful biohorizons for recognition of the lower part of the Upper Barremian and hence for the approximation of the Lower-Upper Barremian boundary. The last occurrences of Rhynchodiniopsis aptiana and Phoberocysta neocomica are calibrated in the basal Aptian.
 
Article
Acritarchs from the interval corresponding to the late Arenigian and early Llanvirnian in British stratigraphy have rarely been described from China, and they are documented herein for the first time. A biostratigraphic correlation of certain acritarch taxa with the Undulograptus austrodentatus graptolite Biozone, which constitutes the base of the Darriwilian Stage, is still premature for China and elsewhere. According to recent studies on different sections from South China, it appears that at least four distinctive species (Ampullula suetica, Dicrodiacrodium ancoriforme, Hoegklintia rayii nov. comb., Liliosphaeridium intermedium) may characterize an interval that corresponds to levels just below or within the Darriwilian Stage. In this context, the acritarch assemblages of the lower to upper Arenigian and of the lower Llanvirnian sequences from different localities of the Yangtze Platform are described. Four acritarch assemblages are distinguished for this time interval and their possible correlations with other areas are discussed.
 
Article
Tresarcus, a new monospecific acritarch genus, is established along with the type-species Tresarcus suecicus sp. nov. It was found in samples from the upper Arenig (Lenodus sp. A conodont Zone) of the Hagudden and Horns Udde sections, Öland, Sweden. The three-arched process tip is a peculiar characteristic of Tresarcus. This structure recalls, from a morphological point of view (though at a different dimensional scale), the four-arched termination of the epidermal hairs that ornate the adaxial (upper) surface of the assimilating leaves of Salvinia natans, Adanson, 1785 (Pteridophyta). This species has an aquatic habit and the four-arched structure as the tip of the epidermal is interpreted as a device that favours buoyancy by trapping air on the leaf surface. A similar function is hypothesized for the three-arched processes of Tresarcus.
 
Article
A restudy of the Ordovician (Arenig-Llanvirn) acritarch taxa Tranvikium polygonale Tynni, 1982, and Ampullula suetica Righi, 1991, indicates that they represent extremes in a single morphological plexus. At one extreme are forms with a polar 'excystment' aperture (closed by an operculum or two opercular pieces) and a smaller opening (plugged or open) at the opposite pole; at the other are forms lacking a polar aperture but having, at the opposite pole, a tube open distally and plugged or open basally. New morphological terms for these structures are proposed. The genera and species are treated as synonyms and an emended diagnosis is given for Tranvikium polygonale, incorporating this whole morphological plexus. The possible purposes of the structures exhibited and the likely affinity of T. polygonale to various groups of algae are discussed. The emendation of Ampullula by Brocke (1997) is rejected and the genus Stelomorpha Yin, 1994 retained, with an emended diagnosis. The new combination Stelomorpha princeps (Brocke, 1997) Uutela and Sarjeant is proposed.
 
Article
The "messaoudensis-trifidum acritarch assemblage" is currently considered to be characteristic of latest Tremadoc-earliest Arenig cold-water environments on the periphery of Gondwana, at high latitudes in the southern hemisphere. An integrated biostratigraphical study on both acritarchs and graptolites was until now only available for localities in northwest England. Reinvestigation of the "messaoudensis-trifidum acritarch assemblage" from the Barriga Formation (Sierra Morena, southwestern Spain), which contains some graptolite horizons that can be attributed to the latest Tremadoc (pre-phyllograptoides and pre-approximatus graptolite biozones), strengthens the biostratigraphical potential of the "messaoudensis-trifidum assemblage", and the importance of some of the acritarch taxa recovered from these levels. It is concluded that the acritarch genera Coryphidium Vavrdová, 1972, Peteinosphaeridium Staplin et al., 1965 emend. Playford et al., 1995, Striatotheca, Burmann, 1970, and the Veryhachium lairdii group (rectangular veryhachiids) appear in the latest Tremadoc, and should not be considered as indicators of the base of the Arenig, as previously suggested.
 
Article
The Lower Palaeozoic sequences west of the Leinster Granite and in the Slievenamon Inlier of southeast Ireland have been palynologically re-investigated. Most of the productive samples yielded sufficient identifiable acritarchs for positive stratigraphical age determinations for several of the formations. The samples also include rare cryptospores, scolecodonts and tubular structures. Previous work in the area west of the Leinster Granite proposed an unbroken succession from Early Ordovician Ribband Group turbidites and volcanics passing up conformably to Early Ordovician to Late Silurian Kilcullen Group. The new palynological data clearly show that the Kilcullen Group in this area is entirely Silurian (Llandovery-early Wenlock) in age, also results obtained from the same group at Slievenamon confirm the previously reported Silurian age. Ordovician acritarchs found in the Kilcullen Group of both study areas are reworked and range in age from late Tremadoc to Llanvirn. The new data reveal a major stratigraphic break between the Ribband Group dated as Early and Middle Ordovician and the Silurian Kilcullen Group. This major break extends some hundreds of kms southwest to the Dingle Peninsula and possibly equates with a similar discontinuity in the Isle of Man to the northeast. This break would thus appear to be a major feature within the northwestern Avalonian margin sequence.
 
Curve of the abundance of chitinozoans, acritarchs and leiospheres in the Upper Ordovician-Silurian sequence in well Nl-2. 
Diagram illustrating the variation of the vesicle length (L) with regard to the chamber diameter (Dp) for Spinachitina oulebsiri sp. nov. (43 specimens from 2656 to 2655.50 m, well Nl-2; flattening corrected with a coefficient of 0.7 for Dp). 
Article
Palynomorph assemblages, especially chitinozoans and acritarchs, from the Upper Ordovician of well Nl-2 (north-east of the Algerian Sahara) are studied in order to precisely date the ultimate effects of the Late Ordovician glaciation and to document the impact of this major climatic stress on the diversity of the palynoplankton. References are made to stable isotope excursions and to global eustatic sea level variations in order to improve the local age determination. The Hassi el Hadjar Formation, i.e. glacio-marine diamictites, is interpreted as a transgressive event resulting from the melting of the northern Gondwana ice cap. It yields poorly preserved and moderately diverse chitinozoans of late Hirnantian age. Acritarchs are more abundant in the lower part of these “microconglomeratic clays”, but display a low diversity and are badly preserved throughout the whole formation. Reworked individuals are recorded in both groups. The marine sediments of the M'Kratta Formation of latest Hirnantian age contain better preserved, more abundant and more diverse palynomorph assemblages, especially in the Upper Member. The composition of this palynoplankton indicates a fairly good faunal and phytoplankton recovery after the early Hirnantian climatic stress.
 
Article
The metasediments of the low-grade metamorphosed Baden-Baden-Gaggenau zone of the northern Schwarzwald (southwestern Germany) have been analyzed palynologically. From 133 samples representing different metasedimentary units, only three samples of the upper part of the Traischbach Serie provide extremely poorly-preserved palynomorphs. The assemblage consists of the galeate acritarch genera Caldariola, Cymatiogaleaand Stelliferidium, as well as specimens of diacromorph and polygonomorph acritarchs. Although determinations are difficult at the generic level and essentially impossible at the specific level, the assemblage can be attributed to an interval between the Late Cambrian and Early Ordovician. This is the first biostratigraphical age assignment for the metasediments of the Baden-Baden-Gaggenau zone, which can possibly be correlated with the Villé Unit of the northern Vosges Mountains (eastern France).
 
Article
Six acritarch species from the Lükati Formation were studied using a combination of techniques, including transmitted light, scanning electron (SEM) and transmission electron (TEM) microscopy. New details of wall ultrastructure, surface microsculpture and internal morphology of the vesicle and processes significantly add to the previously known morphological features and increase the understanding of the form-genera Archaeodiscina, Globosphaeridium, Comasphaeridium, Skiagia, Tasmanites and Leiosphaeridia. Examination of microfossils using TEM revealed a substantial variation in wall ultrastructure among acritarchs. The diversity includes four structural types of vesicle wall in addition to their single- and multi-layered structure and the variable thickness of the wall. These are: electron-tenuous and fibrous; electron-dense and homogeneous; electron-dense and homogeneous but perforated by radial canals; and composite laminated structure. Morphologically recognised groupings of acritarchs (acanthomorphic, disphaeromorphic, sphaeromorphic) and tasmanitid taxa appear to be characterised by particular features of the wall structure, although the wall structure in itself may not be directly indicative of systematic relationships. Structurally diverse vesicle walls are observed in Tasmanites and Leiosphaeridia, taxa that both have been interpreted, based on other lines of evidence, to be of prasinophycean (green algal) affinities. The distinct wall ultrastructure of the Leiosphaeridia studied is similar to that of extant green algal genera, which provides evidence that some Cambrian leiosphaerids were chlorophycean algae, probably related to the Order Chlorococcales. Previous research and interpretations of the wall ultrastructure are also briefly discussed.
 
Article
We sampled and analyzed surface sediments from 31 lakes along a latitudinal transect crossing the coniferous treeline on the Kola Peninsula, Russia. The major vegetation zones along the transect were tundra, birch-forest tundra, pine-forest tundra, and forest. The results indicate that the major vegetation types in our study area have distinct pollen spectra. Sum-of-squares cluster analysis and principal components analysis (PCA) groupings of pollen sites correspond to the major vegetation zones. PCA ordination of taxa indicates that the first axis separates taxa typical of the forest zone (Pinus, Picea) from taxa typical of tundra and forest-tundra zones (Polypodiaceae, Ericaceae, and Betula). The current position of the coniferous treeline, defined in our region by Pinus sylvestris, occurs roughly where Pinus pollen values reach 35% or greater. Arboreal pollen (AP)/non-arboreal pollen (NAP) ratios were calculated for each site and plotted against geographic distance along the transect. AP/NAP ratios of 7 or greater are found within pine-forest tundra and forest vegetation zones. Pinus stomates (dispersed stomatal guard cells) are absent from sites north of the coniferous treeline and all but two samples from the forested sites contain stomates. Stomate concentrations among the samples are highly variable and range from 10 to 458 per ml and positively correlate with the changing Pinus pollen values.
 
Article
The importance of adaptation in determining patterns of evolution has become an important focus of debate in evolutionary biology. As it pertains to paleobotany, the issue is whether or not adaptive evolution mediated by natural selection is sufficient to explain the stratigraphic distributions of taxa and character states observed in the plant fossil record. One means of addressing this question is the functional evaluation of stratigraphic series of plant organs set in the context of paleoenvironmental change and temporal patterns of floral composition within environments. For certain organ systems, quantitative estimates of biophysical performance can be made on the basis of structures preserved in the fossil record. Performance estimates for plants separated in time or space can be compared directly. Implicit in different hypotheses of the forces that shape the evolutionary record (e.g. adaptation, mass extinction, rapid environmental change, chance) are predictions about stratigraphic and paleoenvironmental trends in the efficacy of functional performance. Existing data suggest that following the evolution of a significant structural innovation, adaptation for improved functional performance can be a major determinant of evolutionary changes in plants; however, there are structural and development limits to functional improvement, and once these are reached, the structure in question may no longer figure strongly in selection until and unless a new innovation evolves. The Silurian-Devonian paleobotanical record is consistent with the hypothesis that the succession of lowland floodplain dominants preserved in the fossil record of this interval was determined principally by the repeated evolution of new taxa that rose to ecological importance because of competitive advantages conferred by improved biophysical performance. This does not seem to be equally true for Carboniferous-Jurassic dominants of swamp and lowland floodplain environments. In these cases, environmental disruption appears to have been a major factor in shaping the fossil record. This does not mean that continuing adaptation was not important during this interval, but it may indicate that adaptive evolution was strongest in environments other than those best represented in the paleobotanical record.
 
Article
Tricolpites trioblatus Mildenhall and Pocknall was described from Upper Miocene-Pliocene sediments of New Zealand and attributed to the Hebe complex (Scrophulariaceae), which is common in the New Zealand vegetation, especially in montane and subalpine habitats. Pollen in Miocene-Pliocene sediments in central Australia is identified with T. trioblatus, and the depositional situations included shallow lakes, with fresh or brackish waters, sometimes becoming saline. The affinities of T. trioblatus are re-examined in the light of these disparate environments in Australia and New Zealand. It has been found that all the fossil grains examined are more comparable to pollen of Wilsonia, and perhaps Cressa (Convolvulaceae), than to those of the Hebe complex. Wilsonia and Cressa are found in salt marshes, hence affinities with them are ecologically more credible for central Australia. T. trioblatus is found in late Eocene sediments deposited under episodic marine transgressions; an environment likely to stimulate the evolution of new species tolerant to saline conditions.
 
Article
Ten megaspore species isolated from Moscow Basin lignites of Lower Carboniferous (Viséan) age have been studied by scanning and transmission electron microscopy (SEM and TEM). These species belong to seven megaspore genera: Lagenicula, Sublagenicula, Crassilagenicula, Setosisporites, Zonalesporites, Caudatosporites, and Cystosporites. Megaspores of the genus Caudatosporites have only been described previously from the Duckmantian (Westphalian B); a new species is duly erected. The ultrastructure of megaspore walls from the genera Crassilagenicula and Zonalesporites has not been previously described. This study also places them in context with other contemporaneous megaspores. The study shows that during the Viséan, in the Moscow Basin, megaspores expressed a similar wall ultrastructure despite large differences in external appearance. The genus Crassilagenicula may represent a group of megaspores from plants that had evolved from those bearing gulate megaspores here typified by Lagenicula acuminata, Setosisporites brevispinosus, and Sublagenicula hirsutoida. Zonalesporites brasserti also appears to show affinities to this group, and may be representative of a plant species in a transitional state between the Lagenicula bearing lycopsids and those more isoetalean in nature.
 
Article
Modern soil samples from South Congo were analyzed for pollen content and compared to forest inventories to define modern pollen-vegetation relationships. A correspondence analysis (CA) was applied independently to botanical and pollen data and a hierarchical cluster analysis to pollen data only. Subsequently, a CA using a presence-absence approach has been made to directly compare the two types of data. Results show that the pollen rain and floristic composition of the sampled sites are not directly linked to altitudinal or precipitation gradients, but clear evidence of variation in relation to hygromorphy and soil type is detected. The forests occurring in swampy environments are well differentiated from the forests developed on well-drained soils by pollen and floristic data. Among forests on well-drained soils, a good distinction can be made between those growing on sandy soils and those growing on ferralitic soils. The comparison between pollen spectra and vegetation shows site-to-site variations in pollen assemblages in relation to the floristic heterogeneity of forests, and it appears that few taxa show a good correlation between plant cover and pollen abundance.
 
Article
The conifer, Frenelopsis alata (K. Feistmantel) E. Knobloch (Cheirolepidiaceae), occurring mostly in the Cenomanian of Europe, is revised on the basis of the type material. Its comparison with relevant species of Frenelopsis is discussed.The ovuliferous cone associated with the genus Frenelopsis is recorded for the first time. For the associated ovuliferous cones of Frenelopsis, a new genus, Alvinia, is introduced in a new combination for the type: Alvinia bohemica (Velenovský) comb. n. Its association with Frenelopsis alata is based on the presence of Classopollis pollen adhering to ovuliferous cone scales, and the same type of pollen found in the microsporangiate cone of F. alata, the same cuticle pattern present on ovuliferous cones, sterile twigs and microsporangiate cones of F. alata, and also the co-occurrence of ovuliferous cones or their scales and sterile twigs of F. alata.Large ovuliferous cones of Alvinia bohemica are formed by helically arranged ovuliferous scales subtended by bracts. Each ovuliferous cone scale displays one or two seeds covered by a covering flap, and three appendages, which form distally a funnel-like structure lined in its inner part by long trichomes. Numerous pollen grains of Classopollis adhere to the trichomes, and the structure is considered to function as a protostigmatic area.The ovuliferous cones of Alvinia differ from similar cones of the Cheirolepidiaceae, Hirmeriella and Tomaxellia, mainly in a high state of unification of the ovuliferous cone scale, reduction of appendages and in a presence of the protostigmatic funnel-like structure.The ovuliferous cones, Alvinia bohemica, rarely occur intact, so it is assumed that they disintegrate when mature. It seems likely that they were not woody. This assumption is supported by the flattened appearance of cones and their cone scales in the sediment, their flexibility and the absence of massive coaly matter known from cones of the Taxodiaceae and Cupressaceae. It is proposed that this type of ovuliferous cone scale indicates a specialized type of pollination. In addition, it is suggested that cone scales enclosing seeds play an important role in propagation.
 
Article
Coniferous foliage from the Albian of Alexander Island, Antarctica, is assigned to the Araucariaceae, Podocarpaceae, and Taxodiaceae based on attached or associated fertile remains. Araucarian foliage represented by Araucaria alexandrensis sp. nov. and A. chambersii sp. nov. is associated with ovulate cone scales described as Araucarites wollemiaformis sp. nov. and A. citadelbastionensis sp. nov., respectively. The Podocarpaceae is represented by Bellingshausium willeyii sp. nov. and the Taxodiaceae by Athrotaxites ungeri, both with attached cones. Sterile foliage is widespread belonging to the form genera Podozamites, Elatocladus, Brachyphyllum and Pagiophyllum. The conifers in this Albian southern high-latitude flora make up ca. 15% of the species diversity. Evidence from leaf litter distribution on palaeosols and leaf morphology suggest that the majority of conifers were large canopy-forming trees, although a few were probably small understorey shrubs.
 
Article
Silicified conifer woods are very common in the mid-Cretaceous (Late Albian, 100Ma) Triton Point Member of the Neptune Glacier Formation (Fossil Bluff Group), SE Alexander Island, Antarctica. These occur as up to 7m high in situ tree trunks and stumps rooted in carbonaceous palaeosols and as allochthonous logs and wood fragments in fluvial channel and sheet sandstone facies. Sixty-eight wood samples were examined in this study and were classified in terms of five form taxa using a quantitative approach. Araucarioxylon (1.5% of specimens) is characterised by dominantly multiseriate, alternately arranged bordered pitting on radial tracheid walls and by 1-4 araucarioid cross-field pitting. Araucariopitys (11.8% of specimens) is characterised by dominantly uniseriate tracheid pitting with subordinate biseriate, alternate tracheid pitting and by 1-4 araucarioid cross-field pitting. Podocarpoxylon sp. 1 (63.1% of specimens) is characterised by contiguous, uniseriate tracheid pitting and 1-2 podocarpoid cross-field pits. Podocarpoxylon sp. 2 (22.1% of specimens) is similar to P. sp. 1, differing only in that ray height is lower, tracheid pits are dominantly spaced more than one pit diameter apart and abundant axial parenchyma is present. These first four taxa all possess growth rings with subtle boundaries. Taxodioxylon (1.5% of specimens) is characterised by 1-2 seriate, oppositely arranged, bordered tracheid pitting, 1-2 taxodioid cross-field pitting and very marked ring boundaries. These woods were derived from large trees with basal stump diameters of up to 0.5m and probable heights of up to 29m. Data from leaf traces suggest that Araucariopitys and Podocarpoxylon sp. 1 and sp. 2 (97% of specimens) were evergreen with leaf retention times of >5years. These predominantly evergreen conifer forests grew in a mild, high latitude (75 degrees S) environment during the mid-Cretaceous greenhouse climate phase.
 
Article
The altitudinal vegetation distribution in the northern Andes during glacial time differed from the present-day conditions as a result of temperature and precipitation change. New evidence indicate that as a response to a reduced atmospheric partial CO(2) pressure (pCO(2)), the competitive balance between C(3) and C(4) plants have changed. Effects may have remained virtually undetected in pollen records, but can be observed using a stable carbon isotope analysis. Vegetation dominated by C(4) taxa, belonging to the families Cyperaceae (e.g. Bulbostylis and Cyperus) and Poaceae (e.g. Muhlenbergia, Paspalum and Sporobolus), may have been able to replace for a significant part the modern type C(3) taxa (e.g. species belonging to Carex, Rhynchospora, Aciachne, Agrostis, Calamagrostis, and Chusquea). Impact of reduced glacial atmospheric pCO(2) levels and lower glacial temperatures on the composition and the elevational distribution of the vegetation types is discussed. The present high Andean vegetation communities may differ from the glacial equivalents (non-modern analogue situation). We identified dry Sporobolus lasiophyllus tussock grassland and Arcytophyllum nitidum dwarfshrub paramo as the possible relict communities from glacial time. The effect on previous estimates of paleo-temperatures is estimated to be small.
 
Article
This paper documents the first record of silicified fossil wood from a previously undescribed wood-rich horizon in the Sitakund Anticline, Eastern Bangladesh. The outcrop is composed of cross-stratified, fine-medium grained sandstones with bidirectional cross stratification indicative of a tidal environment, deposited ca. 5-5.2 million years before present (Miocene/Pliocene). The wood is characterised by large solitary vessels with alternate intervascular pits, banded parenchyma, uniseriate rays, and multiseriate rays with one radial canal per ray. This character combination closely resembles the wood of extant Gluta L. of the Anacardiaceae. This specimen has been assigned to the organ genus Glutoxylon Chowdhury erected for fossil woods with anatomical similarity to Gluta (including Melanorrhoea Wall.). The excellent preservation of this mature wood specimen illustrates the potential for using fossil wood from the Sitakund locality for palaeoecological studies in terms of biodiversity and adaptational response to climate change. Moreover such investigations of fossil woods from Bangladesh will compliment studies undertaken on fossil plants in other parts of Central and Southeastern Asia which will further the understanding of plant migration routes between India and Southeast Asia during the Tertiary.
 
Article
A palynological investigation of samples from various boreholes in the Maghrabi Formation (Kharga Oasis, southern Egypt) resulted in the recovery of pollen and spore assemblages associated with rare marine palynofossils (dinoflagellates, foraminiferal linings) and freshwater algae (e.g. Botryococcus, Ovoidites parvus, Pediastrum, Scenedesmus). The general composition of the assemblages is largely consistent with the estuarine and tidal flat conditions characteristic of the Maghrabi Formation.The formal descriptions of the following new taxa are given: Cicatricosisporites kedvesii Schrank, sp. nov., Equisetosporites lawalii Schrank, sp. nov., Dettmannaepollenites clavatus Schrank, sp. nov., and Integritetradites porosus Schrank and Mahmoud, gen. nov. and sp. nov. Combined scanning electron microscopic and light microscopic techniques have been applied to hand-picked grains to illustrate the new taxa. The palynological ages assigned to the Maghrabi samples are mainly based on angiosperm pollen and range from undifferentiated Cenomanian for an Integritetradites porosus assemblage without triporates to Late Cenomanian-Early Turonian for another assemblage which has I. porosus associated with rare triporate pollen grains (Proteacidites/'Triorites' spp.).
 
Article
Lower Old Red Sandstone deposits penetrated by a series of cored boreholes near Newport (South Wales) have been sedimentologically logged, and recovered plant assemblages (microfossil and megafossil) investigated. Sedimentological logging indicates that the deposits are typical of the extensive terrestrial-fluviatile floodplain deposits of the Anglo-Welsh Basin. Palynomorph assemblages have been recovered from a number of horizons and comprise entirely terrestrial forms (spores and phytodebris). They essentially represent a single assemblage, belonging to the middle subzone of the micrornatus-newportensis sporomorph assemblage biozone, and indicate an Early Devonian (mid-Lochkovian) age. The new biostratigraphical data enables correlation with other Lower Old Red Sandstone deposits of the Anglo-Welsh Basin, and the deposits are assigned to the lower part of the St. Maughan's Group. A plant megafossil/mesofossil assemblage recovered from one of the spore-bearing horizons includes a zosterophyll assigned to Zosterophyllum cf. fertile. This is the earliest reported zosterophyll from the Anglo-Welsh Basin. The new palynological/palaeobotanical data provide important information on the palaeoecology and palaeobiogeography of the vegetation of the southeastern margin of the Old Red Sandstone continent during Lochkovian times. Palaeogeographical variation in the distribution of plant microfossils and megafossils is interpreted as reflecting differences between the flora of the lowland floodplain and inland intermontaine basins, although this is to a certain extent overprinted by variation due to localized differences in environmental conditions.
 
Article
Permineralized cones found organically attached to Spaciinodum collinsonii stems are described from the early Middle Triassic silicified flora from the Fremouw Formation of Antarctica, and the species diagnosis is emended to include the reproductive specimens. The apical cones are organized into internodal and leaf-bearing nodal regions. Nodal septations span the central pith and cortex, and thin fimbrils subdivide the internodal areas into smaller chambers. The vascular system consists of 31-33 continuous bundles that do not alternate in position between successive nodes and internodes. Simple sporangia are associated with the cortical chambers and occur in one whorl on the axis. Spores are small, lack elaters, and have no discernible ultrastructure preserved, and they are interpreted to be immature. The Antarctic cones are different in structure from typical cones of modern and fossil members of Equisetales; however, they share similarities with some morphologically aberrant cones of extant Equisetum and several Late Paleozoic and Mesozoic compression-impression fossils. Spaciinodum is now the most complete anatomically described Mesozoic sphenophyte.
 
Article
A reappraisal of chitinozoan distribution across the Ordovician-Silurian boundary on the Island of Anticosti has led to the recognition of a new zone, the Ancyrochitina ellisbayensis biozone, in the uppermost part of the Ellis Bay Formation. This biozone lies between the well defined Upper Ordovician Spinachitina taugourdeaui biozone and the lowest Silurian (Rhuddanian) Plectochitina nodifera biozone of the Becscie Formation. The occurrence of such diagnostic species as P. nodifera, Belonechitina postrobusta, Conochitina electa and Ancyrochitina ramosaspina in the Lower Silurian of Anticosti points to a close similarity to faunas in Estonia and north Latvia and indicates an age ranging from the Parakidograptus acuminatus to the Coronograptus cyphus in terms of graptolite zones. The chitinozoan biozonation harmonizes with that based on conodonts and, to a lesser extent, with the known graptolite faunal succession. Five new species: Ancyrochitina ellisbayensis sp. nov., Clathrochitina postconcinna sp. nov., Conochitina gunriveris sp. nov., Clathrochitina perexilis sp. nov., Bursachitina basiconcava sp. nov. and three species in open nomenclature are described.
 
Article
Deviant forms of polycolpate pollen, differing from the typical pattern in the number and arrangement of apertures, are found to be similar in distantly related dicotyledon taxa. The range of variation of common and deviant aperture patterns may be arranged as a continuous series, which may be described as a gradual and geometrically regular transformation of the deviant form with a meridional circular colpus to one of the common polycolpate conditions. Similar series have been observed in the taxa with colporate and pseudocolpate pollen. All possible spatial isomers and their mirror symmetrical variants of the deviant polycolpate and polypseudocolpate pollen have been predicted in terms of the suggested regularities of aperture multiplication. Some of them have been identified in the samples studied.
 
Article
A late Carboniferous arborescent sphenopsid has been modelled for the first time with the AMAP 1 system. The natural entity consisting of the three form species 'Calamites multiramis/Annularia stellata/Calamostachys tuberculata' (respectively the trunk/branches and foliage/cones) representing the aerial part of this plant is reconstructed and its architecture modelled. The different growth stages are extrapolated, generating a dynamic view that did not exist until now. The model is based on the hypothesis that the modelled part is not preformed but results from the successive production and elongation of internodes. This growth led to old ontogenetic stages of the plant in agreement with Remy and Remy's reconstruction (Remy, W., Remy, R., 1977. Die Floren des Erdaltertums. Verlag Glückauf, Essen, 468 pp.). With its verticillate sterile organs and cone-shaped fructifications similar to the extant herbaceous relative Equisetum, this calamite is distinguished from the latter taxon by having possible 'throw-away' phyllomorphic branches. We assumed the presence of a restricted zone of branches located in the apical part of the trunk. Moreover, the production of reproductive organs that succeeds the vegetative stage implies a major photosynthetic phase associated with a monocarpical form of development of the fossil plant.
 
Article
New fertile specimens of Archaeopteris roemeriana from Upper (but not uppermost) Famennian strata of Belgium have been studied. Crowded sporangia are borne on non-laminate, three times bifurcate fertile leaves helically arranged around the fertile ultimate axes. Vegetative leaves occur both proximal and distal to the fertile leaves. Heterospory is demonstrated with miospores belonging to the Geminospora-Aneurospora complex and macrospores most probably to Contagisporites genus. The established morphological traits allow us to substantiate a synonymy between A. roemeriana and A. halliana. The apparent dominance of A. halliana on the eastern side of the Acadian mountains during Late Famennian times is discussed.
 
Article
The modelling system AMAP 1 provides morphological models that reproduce the series of shapes developed in a plant structure during its growth. It is applicable to plants that have architectural features consistent with the principles introduced by Hallé et al. (Hallé, F., Oldeman, R.A.A., Tomlinson, P.B., 1978. Tropical Trees and Forest. Springer, Berlin, 441 pp.). We present the main principles of the methodology including the use of an architectural template and the statistical processing of the data collected on sample plants and a description of its components and parameters. We use models of Equisetum telmateia aerial shoots as examples of adaptations of this methodology to plants represented by a limited number of specimens. The main features of this approach that make it especially relevant for modelling incomplete and fragmented fossil plants include the use of architectural templates constructed by adding discrete morphological entities limited to a number of axial components as follows: as many branch orders as are identified in the sample plants, a single extension unit per branch order, and its internodes. This approach is viewed as a means to provide visual representations of plants at different ontogenetical stages, expressing our current knowledge of their growth and branching strategies, and of the parameters that control their geometries.
 
Article
Late Ordovician and Early Silurian chitinozoans from the uppermost Vinini Formation, and the Hanson Creek Formation in central Nevada and the lower Cape Phillips Formation, Cape Manning section, in Arctic Canada have been re-investigated and a new chitinozoan biozonation is proposed. The Upper Ordovician of central Nevada can easily be correlated to that of Arctic Canada through the common occurrence of the Ordochitina nevadensis biozone in both regions. No such correlation, however, is possible with the Late Ordovician of Anticosti Island in eastern Canada because of the absence of the index Upper Ordovician chitinozoan zonal species of central Nevada such as Belonechitina tenuispinata sp. nov, Ordochitina nevadensis sp. nov. and Nevadachitina vininica gen. nov., sp. nov. in the former area.One new genus, Nevadachitina, and nine new species, Eisenackitina ripae, Belonechitina martinica, Nevadachitina vininica, Nevadachitina praevininica, Ordochitina nevadensis, Belonechitina tenuispinata, Belonechitina parvispinata, Tanuchitina laurentiana, Angochitina hansonica are described and illustrated in this paper and four species are left in open nomenclature.
 
Article
A palynomorph with an unequivocal relationship to the eight-grain polyads of the mimosoid genus Calliandra Benth., is described from the Miocene sediments of San Juan Province, Argentina. Comparison of the fossil palynomorph with polyads of the extant Calliandra species shows a resemblance to those which have one, highly specialized, appendiculate monad. The new palynomorph has a rudimentary appendix, apparently transitional in the path leading to the more highly developed appendiculate forms in the extant Calliandra group. This specialized polyad type is considered to be one of the most highly evolved forms in subfamily Mimosoideae. The closest affinity of the new fossil polyad is with the eight-grain calymmate polyads of Calliandra chilensis Benth., a species which has developed in the extra-tropical, xerophilous shrub, habitat of north-central Chile. The disappearance of Calliandra species in San Juan Province is thought to be related to the culmination of the Andean rising, and the consequent interruption to the Pacific Ocean climatic influence. This new discovery is the first fossil record of Calliandra for Argentina, as well as being the most southerly and the oldest. It reinforces the hypothesis of an early origin and diversification for the Leguminosae in Tropical America.
 
Article
A small but diverse fossil flora is described from the Early Permian Taiyuan Formation occurring at the Yangshuling mine in Pingquan district of Hebei Province, northern China. Fossils occur as compression/impressions within mudrocks and fine-grained sandstones and also as carbonate permineralizations within volcaniclastic tuffs. All are fragmentary and contain lycopsids, sphenopsids, ferns and seed plants, and include several new species. In the compression assemblage sphenopsid and pteridosperm foliage accounts for the majority of the fossils recognised with only a few other kinds of plant organs present. In contrast, the permineralized assemblage is dominated by cordaitaleans with a composition similar to that occurring in coal-ball assemblages elsewhere in the Taiyuan Formation. From the taxonomic synthesis presented it is apparent that the Yangshuling permineralized assemblage contains many of the plant taxa diagnostic of the northern realm of the Early Permian Cathaysian flora, and preserves a representative sample of the wetland coal-swamp vegetation of this time. The permineralized assemblage at Yangshuling represents the first example of anatomically preserved plants from volcaniclastic lithologies from the Palaeozoic of China, raising the possibility of similarly preserved plant-fossil assemblages elsewhere in the Cathaysian realm.
 
Article
Analysis of 170 pollen assemblages from surface samples in eight vegetation types in the Florida Everglades indicates that these wetland sub-environments are distinguishable from the pollen record and that they are useful proxies for hydrologic and edaphic parameters. Vegetation types sampled include sawgrass marshes, cattail marshes, sloughs with floating aquatics, wet prairies, brackish marshes, tree islands, cypress swamps, and mangrove forests. The distribution of these vegetation types is controlled by specific environmental parameters, such as hydrologic regime, nutrient availability, disturbance level, substrate type, and salinity; ecotones between vegetation types may be sharp. Using R-mode cluster analysis of pollen data, we identified diagnostic species groupings; Q-mode cluster analysis was used to differentiate pollen signatures of each vegetation type. Cluster analysis and the modern analog technique were applied to interpret vegetational and environmental trends over the last two millennia at a site in Water Conservation Area 3A. The results show that close modern analogs exist for assemblages in the core and indicate past hydrologic changes at the site, correlated with both climatic and land-use changes. The ability to differentiate marshes with different hydrologic and edaphic requirements using the pollen record facilitates assessment of relative impacts of climatic and anthropogenic changes on this wetland ecosystem on smaller spatial and temporal scales than previously were possible.
 
Article
The results of a palynological analysis of the sedimentary sequence of Borehole RCH-151, Chuperbhita Coalfield, Rajmahal Basin, Bihar are presented here. The borehole penetrated the Rajmahal Formation (comprising two traps sandwiching an intertrappean bed), the thinly represented Dubrajpur Formation and in its lower part, the Coal Measures. The coal-bearing interval is associated with Scheuringipollenites barakarensis, Faunipollenites varius, Densipollenites indicus, Gondisporites raniganjensis and Densipollenites magnicorpus Assemblage Zones. The presence of these biostratigraphic units indicates correlation with the Barakar Formation (Early Permian) and the Barren Measures and Raniganj Formations (both Late Permian). This is the first record, in the Chuperbhita Coalfield, of Late Permian strata, which appear to represent a condensed sequence. Prior to the present study, the Permian succession was thought to have been associated entirely with the Barakar Formation. The overlying Dubrajpur Formation yielded a distinct spore-pollen assemblage (in association with the first report of dinoflagellate, Phallocysta), which is assigned to the newly identified Callialasporites turbatus palynozone of latest Early to early Middle Jurassic age. The diverse spore-pollen flora of the intertrappean bed (Rajmahal Formation) incorporates several age marker taxa, viz. Undulatisporites, Leptolepidites, Klukisporites, Ruffordiaspora, and Coptospora. The assemblages from intertrappean beds are correlated with the Ruffordiaspora australiensis palynozone of Australia. Thus the palynodating indicates Permian, latest Early to early Mid-Jurassic and Early Cretaceous age for the strata studied. This is the first record of definite Jurassic microfossils from the non-marine sequence of Rajmahal Basin, India.
 
Article
A growing number of studies use the plant species-specific inverse relationship between atmospheric CO2 concentration and stomatal density (SD) or stomatal index (SI) as a proxy for paleo-CO2 levels. A total of 285 previously published SD and 145 SI responses to variable CO2 concentrations from a pool of 176 C3 plant species are analyzed here to test the reliability of this method. The percentage of responses inversely responding to CO2 rises from 40 and 36% (for SD and SI, respectively) in experimental studies to 88 and 94% (for SD and SI, respectively) in fossil studies. The inconsistent experimental responses verify previous concerns involving this method, however the high percentage of fossil responses showing an inverse relationship clearly validates the method when applied over time scales of similar length. Furthermore, for all groups of observations, a positive relationship between CO2 and SD/SI is found in only ≤12% of cases. Thus, CO2 appears to inversely affect stomatal initiation, although the mechanism may involve genetic adaptation and therefore is often not clearly expressed under short CO2 exposure times.
 
Article
More than 300 megaspore specimens have been recovered from samples from the Late Permian, Lower Whybrow coal seam of the Wittingham Coal Measures of the Sydney Basin. Only two species are recognised: Singhisporites surangei (Singh) Potonié, emend. and a new species of Singhisporites. Species distribution within the seam is controlled by a major fire event, as recognised by coal petrology and mesofossil content: Singhisporites surangei is dominant before the event, but following it, it is subordinate to the new species.The abundance of megaspores recovered has allowed recognition of the full range of morphologic variation of Singhisporites surangei, which encompasses specimens assigned previously to Singraulispora Pant & Mishra, 1986 and Mammilaespora Pant & Srivastava, 1961; both are regarded as junior synonyms of Singhisporites Potonié, emend. Ultrastructurally, the new species shows affinities with Mesozoic isoetalean megaspores.
 
Article
Middle Ordovician large organic walled microfossils (chitinozoans, scolecodonts, hydrozoans and foraminiferal linings) were recovered from the upper Goldwyer and lower Nita formations, Canning Basin, Western Australia, from three cores (WMC Santalum 1A, Kunzea 1 and Acacia 2). Petrophysical logs of these cores reveal an overall upward shallowing supersequence, overprinted by numerous transgression/regression couplets that can be correlated over 100km.Analysis of the abundance of the microfossils with respect to the gamma log signatures reveals that both chitinozoan abundance and diversity decrease as water depth shallows; however, the opposite is not always true and other factors probably intervene. Scolecodonts show an increase in abundance in transgressions, while hydrozoans and foraminiferal linings show no consistent response to trangressive or regressive phases. Cyathochitina hunderumensis tends to dominate chitinozoan assemblages where there is a transgression, while species of Belonechitina replace Cy. hunderumensis in regressive phases.
 
Article
Pollen input to the water surfaces of maar crater lakes Barrine and Eacham (1 km² and 0.5 km² respectively, ca. 720 m a.s.l.), surrounded by rainforest in northeastern Australia, were measured in floating Tauber traps for a variety of periods spanning the years 1978 to 1985. The mean weekly total pollen catch is 75% of that estimated for the surrounding region of varied vegetation. Regardless of their sources, the influxes of pollen taxa are unevenly distributed over the lakes' surfaces. There is similar variation through time, with some indication that this might be smoothed over periods of 5 years or more. There are no inflow streams and pollen input down surrounding slopes is negligible. Mean total pollen influx to seston traps close to the lakes' bottoms (1979 to 1988) is <5% of that to the Tauber traps, a discrepancy attributed to trap design. In contrast, mean annual influx measured by the Tauber traps is similar to that estimated from dated sediment samples younger than 1966 AD at Lake Barrine. The proportions of different pollen taxa are less affected by trap position or period of exposure than are their influxes; their mean percentages for Tauber traps, seston traps and sediment samples are all rather similar.
 
Article
Fruits of Restionaceae and seeds of Typhaceae are described from a latest Eocene-Oligocene mudstone underlying oil shales in a subsurface sequence near Rockhampton, coastal central Queensland. The Restionaceae fruits are unilocular and encase a single pendulous orthotropous seed with a structured micropylar cap, which may be tannin filled. These are allocated to Restiocarpum gen. nov., which has as its type Restiocarpum latericum sp. nov., and four other taxa described herein; Restiocarpum tesselatum sp. nov., Restiocarpum verrucatum sp. nov., Restiocarpum laeve sp. nov., and Restiocarpum fusiforme sp. nov. Typhaspermum cooksoniae gen. et sp. nov., which accommodates asymmetric claviform seeds, is interpreted as a member of the Typhaceae based on the presence of a lid-like operculum, bitegmic wall, and chalazal cavity.Reconstruction of the source plant community emphasizes similarities to restiad swamps of present day Wallum (swamp heathland) vegetation which is extensively developed along the Queensland coast. Biogeographic implications for the Restionaceae and Typhaceae are discussed.
 
Article
The Early Miocene vegetation of western Styria, Austria, is reconstructed on the basis of detailed investigations of leaves and diaspores from the mining area Oberdorf N Voitsberg. In this paper, the flora and probable vegetation are compared with other assemblages of similar age from the Czech Republic and Germany to elucidate the diversity of wetland and mesophytic plant communities. The floristic composition and the vegetational units represented in Oberdorf are compared to the middle part of the Most Formation (M Most Fm), Cypris Shale, Mydlovary Formation (Mydlovary Fm) of Bohemia, and the Wackersdorf mining area of Bavaria. Among these sites, Oberdorf is extremely poor in hydrophytes and reed-like monocotyledons, indicating rare pond-like habitats as well as possibly more closed swamp forest conditions than, e.g. in the M Most Fm. In Oberdorf, relatively high pH-values in the lignite-forming swamps and the possible scarcity of acidic, nutrient-poor (sandy) soils have probably influenced the floristic composition of the azonal communities. The peat-forming associations in all regions share the abundance of Glyptostrobus europaeus. However, distinct differences in the accompanying elements, such as Taxodium dubium (present and abundant only in the M Most Fm) indicate even stronger floristic variability of Early(/Middle) Miocene peat-forming and riparian plant communities than previously expected. The virtual absence of Pinus, Engelhardia, Comptonia, and probably also of Quercus kubinyii/Quercus drymeja in the megafossil record of Oberdorf can possibly be explained by the edaphic conditions. The abundance of Sequoia abietina (absent in all the other compared sites), which we assign to riparian (and mesophytic) forests in Oberdorf, may have been favoured by rich alluvial soils.
 
Article
Species of the megaspore genus Minerisporites Potonié, megaspore apparatuses of species of the water fern Azolla Lamarck, and some associated organic-walled microfossils recovered from deposits of the Upper Palaeocene and Palaeocene/Eocene transition in the southern part of the Netherlands and neighbouring Belgium are redescribed on the basis of an examination of specimens under scanning and transmission electron microscopes. Originally studied about 40 years ago by S.J. Dijkstra, the re-examination has enabled emended diagnoses to be produced for six taxa: Minerisporites glossoferus (Dijkstra) Tschudy, M. mirabilis (Miner) Potonié, M. mirabilissimus (Dijkstra) Potonié, Azolla schopfii Dijkstra, A. teschiana Florschütz, and A. velus (Dijkstra) Jain and Hall. In addition, a revised description is provided for massulae of Salvinia Séguier that were originally thought to be megaspores and, hence, named by Dijkstra as Triletes? exiguus. The gross morphology and construction of the exospore of the species of Minerisporites are similar, but nevertheless sufficiently distinct for them to be maintained as separate taxa. Monolete microspores are preserved in hollows in the reticulate surface of some of the specimens of M. mirabilissimus. This is consistent with the presumed isoetalean affinity of Minerisporites. An apparent stratigraphic morphocline from M. glossoferus to M. mirabilis, suggested previously, is confirmed following our reassessment of their characteristics. The species of Azolla are all multi-floated, but they differ from each other in several ways, in particular with respect to the ultrastructure of the megaspore wall. They are also distinct from all other species that have been considered in sufficient detail for satisfactory comparisons to be made. The massulae of A. teschiana are described for the first time. The floats in A. velus are attached to the proximal part of the megaspore only by suprafilosal hairs. There are no maniculae. It is argued that these structures do not exist in either this or any other species of Azolla. Whole fertile fossil remains that demonstrate the nature and habitat of the living plants are known for all three genera. Hence, their reproductive structures can be used with confidence in palaeoenvironmental interpretation. The overall assemblage, which also includes a few specimens of the marsilealean megaspore Molaspora lobata (Dijkstra) Hall, undoubtedly reflects the presence of lowland aquatic and semi-aquatic vegetation.
 
Article
Ordovician palynologic studies started in the 1930s when Eisenack first described Palaeozoic "hystrichospheres" (later named acritarchs), and defined the chitinozoans and melanosclerites. During the ensuing two decades, Ordovician palynologic investigations were mostly descriptive. It was the rise of the oil industry in the 1950s and 1960s, which accelerated palynologic research, particularly with the recognition that acritarchs and chitinozoans were biostratigraphically important groups for Ordovician stratigraphy. Today, more than 700 publications deal with Ordovician acritarchs, and about 400 papers concern Ordovician chitinozoans. In addition to these two palynomorph groups, other less important organic-walled microorganisms have been studied. These include plant remains (spores, cuticles), scolecodonts and such enigmatic groups as the melanosclerites and the mazuelloids. This paper summarises the research on Ordovician palynomorphs during the 20th century and looks ahead to the types of research that may be important and most fruitful for Ordovician palynology at the beginning of the new millenium. Particular attention is paid to the C.I.M.P./I.G.C.P. no. 410 joint meeting "Ordovician Palynology and Palaeobotany," held in Prague during the 8th International Symposium on the Ordovician System. A brief account is given concerning the global Ordovician chronostratigraphy and the correlation of the main regional series and stages.
 
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An ultrastructural transmission electron microscope (TEM) study of fossil leaf cuticles from the Jurassic pteridosperm Komlopteris nordenskioeldii (Nathorst) Barbacka from the Mecsek Mountains (South Hungary) was conducted. Remnants of cuticles of leaves originating from so-called "sun and shade" environments were sectioned with a diamond knife, transversally as well as longitudinally. Although the present study showed a simple type of cuticle in this pteridosperm, differences were observed in the occurrence of its components, such as electron lucent amorphous material and various densities of granules, which give rise to different zones. The included fibrilous elements appeared to be made of aggregated and aligned granules, equivalent in size and electron density to nearby non-fibrilous granular regions. The combinations of these ultrastructural features allow distinctions between four types of cuticle: sun upper, sun lower, shade upper and shade lower. Considering the distinction made earlier in two types of cuticle and supposed to be related to sun and shade on the basis of macroscopical and microscopical features, four types only on the basis of differences in thickness, the present study reinforces the distinctions with ultrastructural microcharacteristics. As this study shows the variations in ultrastructure of cuticle among the four types, the differences observed may reveal the great sensitivity of some plants to environment. At the same time, it points out the importance, in ultrastructural studies of cuticles, of studying a number of samples for one taxon.
 
Top-cited authors
Bas van Geel
  • University of Amsterdam
Hans Kerp
  • University of Münster
José Carrión
  • University of Murcia
Hermann Behling
  • Georg-August-Universität Göttingen
Johanna H.A. van Konijnenburg-van Cittert