Mesofossil Floras Research Articles

Morphology and ultrastructure of cicatricose spores found in an isolated sporangium-bearing structure of a schizaealean fern from the Lower Cretaceous rocks at Casal do Borracho, Torres Vedras, western Portugal

Fossil spores provide important insights into the evolutionary history of ferns, including their morphological changes and adaptations over time. The morphology and ultrastructure of trilete spores with cicatricose sculpture composed of sets of parallel or near-parallel ribs (muri) have been studied. Observations on the spores were performed using light microscopy, scanning electron microscopy, and transmission electron microscopy. The cicatricose spores were extracted from a single sporangium-bearing structure collected from Casal do Borracho mesofossil flora near Torres Vedras (Lusitanian Basin, western Portugal) from sediments belonging to the Almargem Formation, considered to be of late Barremian or early Aptian age (and possible younger than that). The sporangium-bearing structure of a schizaealean fern and in situ cicatricose spores are compared with the family Anemiaceae. On the basis of spore size and shape, laesura length, with about 20 proximal narrow ribs, oriented perpendicular to the spore sides, and three sets of distal ribs forming V-shaped patterns, the cicatricose spores in the present study are clearly assigned to the fossil-taxon Cicatricosisporites venustus. The spore ultrastructure includes a homogeneous exospore of a blechnoid type with a slight difference in the thickness in the proximal, distal, and equatorial regions. The morphology and ultrastructure of the studied spores are corresponded to Anemia type.

Cretaceous chloranthoids: early prominence, extinct diversity and missing links.

The Chloranthaceae comprise four extant genera (Hedyosmum, Ascarina, Chloranthus and Sarcandra), all with simple flowers. Molecular phylogenetics indicates that the Chloranthaceae diverged very early in angiosperm evolution, although how they are related to eudicots, magnoliids, monocots and Ceratophyllum is uncertain. Fossil pollen similar to that of Ascarina and Hedyosmum has long been recognized in the Early Cretaceous, but over the last four decades evidence of extinct Chloranthaceae based on other types of fossils has expanded dramatically and contributes significantly to understanding the evolution of the family. Studies of fossils from the Cretaceous, especially mesofossils of Early Cretaceous age from Portugal and eastern North America, recognized diverse flowers, fruits, seeds, staminate inflorescences and stamens of extinct chloranthoids. These early chloranthoids include forms related to extant Hedyosmum and also to the Ascarina, Chloranthus and Sarcandra clade. In the Late Cretaceous there are several occurrences of distinctive fossil androecia related to extant Chloranthus. The rich and still expanding Cretaceous record of Chloranthaceae contrasts with a very sparse Cenozoic record, emphasizing that the four extant genera are likely to be relictual, although speciation within the genera might have occurred in relatively recent times. In this study, we describe three new genera of Early Cretaceous chloranthoids and summarize current knowledge on the extinct diversity of the group. The evolutionary lineage that includes extant Chloranthaceae is diverse and abundantly represented in Early Cretaceous mesofossil floras that provide some of the earliest evidence of angiosperm reproductive structures. Extinct chloranthoids, some of which are clearly in the Chloranthaceae crown group, fill some of the morphological gaps that currently separate the extant genera, help to illuminate how some of the unusual features of extant Chloranthaceae evolved and suggest that Chloranthaceae are of disproportionate importance for a more refined understanding of ecology and phylogeny of early angiosperm diversification.

The Cretaceous diversification of angiosperms: perspectives from mesofossils

Abstract The plant fossil record during the Cretaceous documents a major transition in the dominant group of terrestrial autotrophs, as plant communities from the earlier Mesozoic were transformed by the appearance and rapid diversification of angiosperms. This transformation began in the Early Cretaceous, continued through the Late Cretaceous and led ultimately to the dominance of angiosperms in most terrestrial ecosystems today, which had profound consequences for the other organisms inhabiting terrestrial ecosystems and perhaps the planet as a whole. Our understanding of angiosperm diversification has been greatly improved over the past 50 years by integrated studies of fossil assemblages containing angiosperm pollen and leaves, but especially by new information from mesofossil floras that have provided previously unanticipated detail on floral form in Cretaceous angiosperms and have allowed the recognition of key dispersed pollen types in situ . Information from fossil flowers has greatly facilitated meaningful comparisons with living plants and integration with phylogenetic analyses of extant angiosperms based on DNA evidence. The combined insights from these discoveries provide a broadly consistent and coherent picture of angiosperm evolution through the Cretaceous, which comprises more than half of their entire evolutionary history.

Fossil mosses from the Early Cretaceous Catefica mesofossil flora, Portugal – a window into the Mesozoic history of Bryophytes

A diverse assemblage of mosses from the Early Cretaceous Catefica mesofossil flora, Portugal, is described based on fragments of charcoalified and lignitized gametophytes and a single spore capsule. Nine different gametophyte morphologies are recognized and assigned to Sphagnopsida, Polytrichopsida and Bryopsida. None of the fossils can be included in any extant species. Four species have character combinations not known in any extant genera and are accommodated in three new genera as Chlorosphagnum cateficense gen. et sp. nov. (Sphagnales, family incertae sedis), Physcidium tortuosum gen. et sp. nov. and Physcidium simsimiae sp. nov. (Diphysciales, Diphysciaceae), and Canaliculidium fissuratum gen. et sp. nov. (Dicranales, Leucobryaceae). Three other species can be assigned to extant genera and are described here as Polytrichastrum incurvum sp. nov. (Polytrichales, Polytrichaceae), Dicranodontium minutum sp. nov. and Campylopus lusitanicus sp. nov. (both Dicranales, Leucobryaceae). One additional specimen has features suggesting affinity with Leucobryaceae but lacks characters critical for a definite generic placement. A single spore capsule is unassigned but is similar to capsules of members of the Ditrichaceae (Dicranales). All the fossil mosses recognised in the Catefica mesofossil flora are assigned to orders of extant mosses that diverged prior to the diversification of the Bryidae, the most diverse clade of living mosses. Based on extrapolations from their nearest living relatives, the Catefica mosses likely grew in more or less open environments, and in moist or wet sites that were primarily of low pH and low nutrient status.

Extinct seed plant diversity in the Early Cretaceous: An enigmatic new microsporangiate fossil with Decussosporites pollen in situ

A new microsporangiate cone, Renbernia zhoui, is described from the mesofossil flora extracted from exposures of the Potomac Group at Puddledock, Virginia, U.S.A., which are of Early Cretaceous (early-middle Albian) age. The cone consists of densely arranged dorsiventrally flattened laminar, flabelliform microsporangiophores that bear two elongate microsporangia on the presumed abaxial surface. The microsporangia are separated by sterile tissue that expands apically into a prominent hood-like sterile extension. The microsporangia have extrorse valvate dehiscence and both microsporangia and sterile apical expansion are covered by a short stiff hairs. In situ pollen resembles Decussosporites, elliptical with a long median colpus on the presumed distal surface flanked laterally by two equally long lateral colpi. A short transverse colpus on the presumed proximal surface links the two lateral colpi and divides the grain into two parts creating the appearance of two sacci. Renbernia zhoui is similar to Brenneria potomacensis described from the slightly older Drewry's Bluff and Dutch Gap mesofossil floras from the Potomac Group that also has Decussosporites-type pollen in situ. However, Renbernia microsporangiophores are more distinctly laminar and have sporangia that are more prominently elongated and with a hood-like apical extension of sterile tissue. The in situ pollen is also much smaller, the pollen wall is much more distinctly perforate-foveolate rather than more or less psilate, and in Renbernia the saccus-like structures are not inflated. The relationship of Brenneria and Renbernia, as well as the possible link between Decussosporites-type pollen and pollen of Eucommiidites (Erdtmanithecales) is discussed.

Frenelopsis antunesii sp. nov., a new cheirolepidiaceous conifer from the Lower Cretaceous of Figueira da Foz Formation in western Portugal

Shoots of cheirolepidiaceous conifers assigned to the fossil genus Frenelopsis are very common in Portuguese Early Cretaceous mesofossil floras. In this study, a new cheirolepidiaceous conifer Frenelopsis antunesii is described from the Lower Cretaceous (upper Aptian –lower Albian) of Figueira da Foz Formation at the Carregueira site, close to the small village of Juncal, in western-central mainland Portugal. The new fossil conifer is described based on morphological characters of vegetative shoots and cuticular features. The new species, Frenelopsis antunesii, is characterised by branching segmented shoots with three leaves per node, leaf surfaces distinctly covered by trichomes, leaves with thick cuticles and stomata arranged in short rows. The stomatal apparatus is composed of four or rarely five subsidiary cells. The morphological and anatomical features documented here support the view that Frenelopsis antunesii likely grew in a semiarid to arid climate.

A Lower Cretaceous palynoflora from Carregueira (Lusitanian Basin, westernmost Iberia): taxonomic, stratigraphic and palaeoenvironmental implications

Here we describe a new Lower Cretaceous palynoflora from the Lusitanian Basin, located in the westernmost sector of the Iberian Peninsula. The spore-pollen assemblage was extracted from samples collected in the Carregueira clay pit complex, located near the village of Juncal, western Portugal, from sedimentary deposits belonging to the Figueira da Foz Formation. A rich and well-preserved palynoflora, typical of non-marine fluvial environments, was recovered. Fifty-eight species and morphological groups of palynomorphs in 43 genera were recognized. The palynoflora is dominated by fern spores and conifer pollen. Angiosperm pollen is scarce and mainly represented by Afropollis, Clavatipollenites, Stellatopollis and Senectotetradites. Comparisons with described marine sections in Portugal suggest that the fossil horizon is lower Albian, corresponding to a hiatus between Zone I and Zone II in the Potomac Group of the eastern USA. The same beds contain a mesofossil flora dominated by angiosperm seeds, fruits and flowers. A similar contrast in the relative abundance of angiosperm mesofossils and pollen is seen at other Portuguese localities but is not evident in the Potomac Group. The palynoflora and the sedimentological data suggest deposition in wet lowland environments in a moderately humid regional setting.

Plant mesofossils from the Late Cretaceous Klikov Formation, the Czech Republic

Late Cretaceous mesofossils are described from the Zliv-Řídká Blana locality in the South Bohemian Basins, the Czech Republic. Angiosperm remains dominate the fossil assemblage both in terms of taxonomic diversity and quantitatively, with about 65 different species based on about 1,000 specimens of flowers, fruits and seeds. There are surprisingly few nonangiosperm species in the flora, with only four specimens assigned to bryophytes, ferns and conifers. There are no megaspores of Selaginellales or Salviniales, which are otherwise common in many Cretaceous mesofossil floras. Among angiosperms, flowers and fruits assigned to the Normapolles group (Fagales) and to the Ericales are particularly prominent. In systematic composition as well as general organization and size of the angiosperm reproductive organs, the Zliv-Řídká Blana mesofossil flora is comparable to other Late Cretaceous mesofossil floras collected from various regions of Laurasia. In addition to the plant remains, the fossil assemblage also includes insect eggs and coprolites.

Melloniflora, a New Extinct Multiparted Flower from the Early Cretaceous of Virginia, USA

Premise of research. The Puddledock mesofossil flora from Virginia is the richest source for studying structurally preserved plant fossils in the Early Cretaceous Potomac Group sequence. Together with other mesofossil floras from the Potomac Group and also from Portugal, it is key for direct assessment of the structure, relationships, and reproductive biology of early angiosperms. In this study, a new multiparted floral structure from the Puddledock locality is analyzed, and its phylogenetic relationships are discussed.Methodology. The fossil was extracted from unconsolidated clays and sands through sieving in water. Adhering sediment was removed using HF and HCl followed by rinsing in water. External and internal features were studied using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy. Phylogenetic analyses were carried out by adding the features of the fossil flower to an existing morphological data set for extant angiosperms.Pivotal results. A new taxon, Melloniflora virginiensis gen. et sp. nov., is established on the basis of a small multiparted floral structure that has several series of free stamens (ca. 50) and carpels (21) borne on a flattened receptacle. Stamens have a broad, short base, and dehiscence is introrse. Ovules are borne in two rows on either side of the ventral suture of the carpels. Abundant secretory cells occur in all tissues. Melloniflora is related to extant early-diverging members of the Magnoliales but also has features found among extant taxa of other early-diverging angiosperm lineages such as Austrobaileyales.Conclusions. Melloniflora adds to the knowledge of plants related to extinct magnoliids from the Early Cretaceous. It shows a combination of features not seen in any extant taxon. Melloniflora contributes to the evidence of considerable extinct diversity at an early stage in angiosperm evolution, especially among clades that today are represented by only a few relatively species-poor lineages.

Callialastrobus sousai gen. et sp. nov., a new araucariaceous pollen cone from the Early Cretaceous of Catefica (Lusitanian Basin, western Portugal) bearing Callialasporites and Araucariacites pollen

A new araucariaceous pollen cone Callialastrobus sousai gen. et sp. nov. is described from the Early Cretaceous (late Aptian–early Albian) Catefica mesofossil flora in the Lusitanian Basin, Estremadura region, western Portugal. The material comprises a single dispersed pollen cone showing peltate deltoid microsporophylls arranged in a helix. Each microsporophyll bears three pollen sacs with Araucariacites and Callialasporites pollen-types in situ. Based on the overall morphology of the pollen cone, the presence of three pollen sacs per sporophyll and the occurrence of Araucariacites pollen grains, the new pollen cone is assigned to Araucariaceae. The new genus Callialastrobus is established here to accommodate araucariaceous pollen cones containing both Araucariacites and Callialasporites pollen-types in situ.

Battenispermum hirsutum gen. et sp. nov., a new Early Cretaceous seed from Portugal with chlamydospermous organisation

A new genus and species, Battenispermum hirsutum, is described from the Early Cretaceous mesofossil flora of Catefica, Portugal. The new taxon is based on five ovulate structures with up to three seeds surrounded by an outer cup formed from partly fused bracts. The seeds are small, about 2.4–3.3 mm long and 1.0–1.6 mm wide, orthotropous with a chlamydospermous organisation. The nucellus is surrounded by a thin integument, a sclerenchymatic inner seed envelope and an additional outer envelope of four bracts, fused for most of their length. The seeds are three- or four-angled in transverse section and elliptical in lateral view with the free tips of the outer envelope forming short, apical projections around the micropyle. The outer surface of the inner seed envelope is almost smooth, while the abaxial surfaces of both inner and outer bracts of the compound ovulate structures are covered by a dense indumentum of long and stiff trichomes. Battenispermum hirsutum clearly belongs to the chlamydospermous BEG complex (Bennettitales-Erdtmanithecales-Gnetales), but it is distinguished from all previously described fossils by the presence of two distinct seed envelopes, a feature otherwise known only for extant Gnetum. The seeds of Battenispermum hirsutum differ, from those of extant Gnetum in other features, including the much simpler micropylar region.

The Early Cretaceous Mesofossil Flora of Torres Vedras (Ne of Forte Da Forca), Portugal: A Palaeofloristic Analysis of an Early Angiosperm Community

Abstract An Early Cretaceous mesofossil flora is described from the lower part of the Almargem Formation (late Barremian-early Aptian) from Torres Vedras (NE of Forte da Forca), Portugal. The flora is the oldest mesofossil flora containing angiosperm remains to be described in detail based on well-preserved flower, fruit and seed remains. In addition to angiosperms, the mesofossil flora also includes megaspores, sporangia and tiny leaves of spore-bearing plants. There are also twigs, cone fragments and seeds of conifers and seeds assigned to the BEG group. In total about 100 species have been distinguished. Most abundant in terms of plant fragments identified, are spore-bearing plants and conifers. Although only about 18 % of the specimens can be attributed to angiosperms, angiosperm diversity is unexpected high considering the age of the flora. Angiosperms account for about 62 % of all species recognized. Angiosperm diversity is mainly at the level of ANA-grade angiosperms, eumagnoliids and in a few cases early diverging lineages of monocots. Eudicots are subordinate. Twenty new genera and 28 new species of angiosperms are established (Anaspermum operculatum gen. et sp. nov., Appofructus nudus gen. et sp. nov., Appomattoxia minuta sp. nov., Burgeria striata gen. et sp. nov., Canrightia elongata sp. nov., Choffaticarpus compactus gen. et sp. nov., Dejaxia brevicolpites gen. et sp. nov., Dinisia portugallica gen. et sp. nov., Eckhartia brevicolumella gen. et sp. nov., Eckhartia longicolumella sp. nov., Eckhartia intermedia sp. nov., Eckhartianthus lusitanicus gen. et sp. nov., Eckhartiopsis parva gen. et sp. nov., Gastonispermum antiquum sp. nov., Goczania rugosa gen. et sp. nov., Goczania inaequalis sp. nov., Goczania punctata sp. nov., Ibrahimia verminculata gen. et sp. nov., Juhaszia portugallica gen. et sp. nov., Kempia longicolpites gen. et sp. nov., Kvacekispermum costatum sp. nov., Mcdougallia irregularis gen. et sp. nov., Nicholsia brevicolpites gen. et sp. nov., Piercipollis simplex gen. et sp. nov., Reyanthus lusitanicus gen. et sp. nov., Samylinaea punctata gen. et sp. nov., Teebacia hughesii gen. et sp. nov., Vedresia elliptica gen. et sp. nov.). Comparison with results of a palynological study from the same horizon that yielded the mesofossil flora shows a marked underestimation of angiosperm diversity in the palynoflora, a pattern that has also been recognized elsewhere.

Extinct Diversity among Early Cretaceous Angiosperms: Mesofossil Evidence of Early Magnoliales from Portugal

Premise of research. Small angiosperm fossils are diverse in Early Cretaceous mesofossil floras from Portugal and eastern North America. Investigations of these fossils have revealed an unexpectedl...

Chlamydospermous Seeds Document the Diversity and Abundance of Extinct Gnetalean Relatives in Early Cretaceous Vegetation

Premise of research. The recognition of diverse and abundant chlamydospermous seeds from the Early Cretaceous of Denmark, Portugal, and eastern North America has been an unexpected outcome of studies of mesofloras that were initially focused on early angiosperms. These seeds provide structural information critical for understanding morphological and structural diversity in an important Mesozoic group of extinct gnetalean relatives. Methodology. The fossil seeds were picked from Early Cretaceous mesofossil floras from localities in western Portugal and Virginia using a stereomicroscope. Selected seeds were studied in more detail for morphological and anatomical traits using SEM and synchrotron radiation X-ray tomographic microscopy. Pivotal results. Six new species of chlamydospermous seeds are described that add substantially to the known diversity of Early Cretaceous chlamydosperms. In general seed organization, the fossils are similar to seeds of extant Gnetales, but none of the fossils can be assigned to any of the three living genera of Gnetales (Ephedra, Gnetum, and Welwitschia). All six species have similar closure of the micropylar canal but show considerable variation in the anatomy of the seed envelope. In micropylar closure, the fossils are most similar to extant Gnetum, but they differ in other respects from seeds of extant Gnetum, and one of the new seed taxa has polyplicate, ephedroid pollen in the micropyle. A well-preserved embryo with two cotyledons is preserved in seeds of Rothwellia foveata and provides the first information on the embryo in this Early Cretaceous chlamydospermous complex. Conclusions. The chlamydospermous seeds described here show similarities to seeds of extant Gnetales. However, most of the fossils exhibit combinations of features that are unknown among extant species of Gnetales and clearly represent an extinct complex of plants that were important in Early Cretaceous vegetation, along with other extinct plant groups, including Bennettitales and Erdtmanithecales.

Some Conifers from The Early Cretaceous (Late Aptian – Early Albian) of Catefica, Lusitanian Basin, Western Portugal

Several mesofossil floras discovered in the Early Cretaceous rocks from the Lusitanian Basin of western Portugal comprise numerous well-preserved conifer remains. Here we report the occurrence of four conifer types in the mesofossil flora from the Catefi ca locality, about 4 km south of Torres Vedras in the Estremadura region on the western Portuguese Basin. The specimens were recovered from rocks belonging to the Almargem Formation, interpreted to be of late Aptian - early Albian age. It includes three Cheirolepidiaceae genera Frenelopsis SCHENK, Pseudofrenelopsis NATH. and Watsoniocladus V.SRINIV., and one conifer twig of Pagiophyllum-type. These conifers, which co-occurred in the same depositional bed with a well-diversified early angiosperm assemblage including flowers, seeds, fruits and dispersed stamens with pollen in situ, provide new insights into Early Cretaceous palaeoecology.

The Nossa Senhora da Luz flora from the Early Cretaceous (early Aptian-late Albian) of Juncal in the western Portuguese Basin

AbstractA new fossil flora is described from the Early Cretaceous of the western Portuguese Basin, based on a combined palynological-mesofossil study. The fossil specimens were extracted from samples collected in the Nossa Senhora da Luz opencast clay pit complex near the village of Juncal in the Estremadura region. The plant-bearing sediments belong to the Famalicão Member of the Figueira da Foz Formation, considered late Aptianearly Albian in age. The palynological assemblage is diverse, including 588 spores and pollen grains assigned to 30 genera and 48 species. The palynoflora is dominated by fern spores and conifer pollen. Angiosperm pollen is also present, but subordinate. The mesofossil flora is less diverse, including 175 specimens ascribed to 17 species, and is dominated by angiosperm fruits and seeds. The mesofossil flora also contains conifer seeds and twigs as well as fossils with selaginellaceous affinity. The fossil assemblage indicates a warm and seasonally dry climate for the Nossa Senhora da Luz flora.

Rightcania and Kvacekispermum: Early Cretaceous Seeds From Eastern North America and Portugal Provide Further Evidence of the Early Chloranthoid Diversification

Abundant flowers, fruits, seeds and stamens that are closely related to extant Chloranthaceae have been reported from the Early Cretaceous floras of Portugal. Among these are small berries with endotestal seeds assigned to the extinct genera Canrightia and Canrightiopsis. Here we describe two new genera, each including a single species, based on fossil fruits and seeds from the Early Cretaceous of eastern North America and Portugal. Both genera have pendent, orthotropous, bitegmic and endotestal ovules/seeds, in which the endotesta consists of a layer of cubic to palisade-shaped crystal cells with endoreticulate fibrous infillings, a combination of features that also characterize Canrightia and Canrightiopsis and that among extant angiosperms are known only for members of the Chloranthaceae. Rightcania kvacekii gen. et sp. nov. from the early to middle Albian Puddledock mesofossil flora of Virginia, USA, is the first representative in the Early Cretaceous floras of North America of a chloranthaceous fossil related to Canrightia and Canrightiopsis. It has three- to five-seeded fruits very similar to fruits and seeds of Canrightia, also with a pronounced tegmen that probably functioned as a nutritive tissue for the developing embryo. Fruits and seeds of Rightcania are larger than those of Canrightia, and also differ in details of the seed coat. Kvacekispermum rugosum gen. et sp. nov. is rare in the late Aptian to early Albian Portuguese mesofossil flora from Vale de Água. It differs from Canrightiopsis in the coarsely rugulate outer surface of the endotesta and its larger size, but is closely similar in the general structure of seed coat and nutritive tissue. Together, Rightcania and Kvacekispermum provide further evidence of the early diversity achieved by chloranthoid angiosperms before the end of the Early Cretaceous.

Extinct Taxa of Exotestal Seeds Close to Austrobaileyales and Nymphaeales From the Early Cretaceous of Portugal

Early Cretaceous mesofossil floras from Portugal and North America include a surprising diversity of small, bitegmic angiosperm seeds with a hard exotestal seed coat. This study describes six different kinds of these seeds from three Portuguese mesofossil localities; Vale de Agua, Torres Vedras, and especially from Famalicão, which has yielded a flora exceptionally rich in exotestal seeds. All the seeds are almost smooth with a characteristic jigsaw puzzle-shaped surface pattern that is formed from the strongly undulate anticlinal walls of the sclerenchyma cells that comprise the exotesta. Several specimens have internal details preserved, including remains of a cellular nutritive tissue interpreted as endosperm, and a tiny embryo with two rudimentary cotyledons. Based on differences in details of the seed coat, and configuration of hilum and micropyle, the fossil seeds are assigned to six new genera, as six new species: Gastonispermum portugallicum gen. et sp. nov., Pazlia hilaris gen. et sp. nov., Pazliopsis reyi gen. et sp. nov., Reyispermum parvum gen. et sp. nov., Lusitanispermum choffatii gen. et sp. nov. and Silutanispermum kvacekiorum gen. et sp. nov. The characteristic exotestal cells with undulate anticlinal walls, details of the hilar and micropylar region, together with the tiny dicotyledonous embryos with rudimentary cotyledons, suggest close relationships to seeds of Nitaspermum and Tanispermum described previously from Early Cretaceous mesofossil floras from eastern North America. These exotestal seeds from Portugal and North America indicate the presence of diverse extinct early angiosperms close to the lineages that today include extant Austrobaileyales and Nymphaeales.

Paisia, an Early Cretaceous eudicot angiosperm flower with pantoporate pollen from Portugal

A new fossil angiosperm, Paisia pantoporata, is described from the Early Cretaceous Catefica mesofossil flora, Portugal, based on coalified floral buds, flowers and isolated floral structures. The flowers are actinomorphic and structurally bisexual with a single whorl of five fleshy tepals, a single whorl of five stamens and a single whorl of five carpels. Tepals, stamens and carpels are opposite, arranged on the same radii and tepals are involute at the base clasping the stamens. Stamens have a massive filament that grades without a joint into the anther. The anthers are dithecate and tetrasporangiate with extensive connective tissue between the tiny pollen sacs. Pollen grains are pantoporate and spiny. The carpels are free, apparently plicate, with many ovules borne in two rows along the ventral margins. Paisia pantoporata is the oldest known flower with pantoporate pollen. Similar pantoporate pollen was also recognised in the associated dispersed palynoflora. Paisia is interpreted as a possibly insect pollinated, herbaceous plant with low pollen production and low dispersal potential of the pollen. The systematic position of Paisia is uncertain and Paisia pantoporata most likely belongs to an extinct lineage. Pantoporate pollen occurs scattered among all major groups of angiosperms and a close match to the fossils has not been identified. The pentamerous floral organisation together with structure of stamen, pollen and carpel suggests a phylogenetic position close to the early diverging eudicot lineages, probably in the Ranunculales.

Vegetational composition of the Early Cretaceous Chicalhão flora (Lusitanian Basin, western Portugal) based on palynological and mesofossil assemblages

A new Early Cretaceous flora is described from the Lusitanian Basin in the Estremadura region (western Portugal) based on a combined study of mesofossils and palynomorphs. The fossil specimens were extracted from samples collected in the Chicalhão clay pit complex, near the village of Juncal from sediments belonging to the Figueira da Foz Formation. The plant bearing sequence is considered to be of Late Aptian–Early Albian age. Palynomorphs and mesofossils are generally well-preserved and include about 63 taxa. The palynoflora is dominated by conifer pollen and fern spores. Angiosperm pollen is also present, but subordinate among the palynomorphs. In contrast, angiosperms completely dominate the mesofossil flora and are mainly represented by fruits and seeds. Four taxa of angiosperm flowers were also identified. The combined palaeobotanical and sedimentological evidence indicates seasonally dry climate and an open vegetation consisting of a mixed conifer forest with an understorey and ground cover of ferns and angiosperms and with patchy occurrences of lycophytes and plants of the Bennettitales–Erdtmanithecales–Gnetales (BEG) group. Angiosperms probably inhabited moister areas bordering rivers and lakes.