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Premise of research. Early Cretaceous flowers recovered from Portugal and North America are some of the oldest and most informative angiosperm structures known. Analyses of this material provide a more direct basis for inferring floral structure and biology in early angiosperms than extrapolations based solely on extant taxa, and they have documented an unanticipated diversity of angiosperms, including the presence of many extinct forms, during the Early Cretaceous. The fossil flower described here from the Early Cretaceous of Portugal adds to the knowledge of this extinct diversity. Methodology. Coalified fossil flowers were extracted from unconsolidated sediments and cleaned with HF, HCl, and water. Details were studied using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy. Phylogenetic relationships were evaluated by adding the fossil to a phylogenetic analysis of extant basal angiosperms based on morphological characters but constrained according to a topology based on molecular data. Pivotal results. A new genus and species, Catanthus dolichostemon, are described on the basis of the fossil flowers. The perianth consists of three thick sepal-like tepals in an outer whorl and six thinner petallike tepals in two inner whorls. The androecium consists of several whorls of stamens with long, broad filaments and anthers with extrorse dehiscence. Pollen is trichotomocolpate and possibly monocolpate. The gynoecium is superior and apocarpous, consisting of six or, rarely, five carpels. Analysis of the phylogenetic position of Catanthus suggests a relationship to Canellales and Magnoliales. Conclusions. Catanthus is a new Early Cretaceous magnoliid angiosperm for which the relationship to the two major clades of extant magnoliids (Laurales 1 Magnoliales or Canellales 1 Piperales) is not resolved securely. Catanthus adds to the evidence of substantial extinct diversity among early angiosperms, including the presence of extinct forms related to extant magnoliids, and it is consistent with a general pattern that angiosperm assemblages from the middle Albian and earlier are dominated by noneudicots.

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.

Three new genera, Atlantocarpus, Lambertiflora and Mugideiriflora, are described from the Early Cretaceous of North America and Portugal based on floral structures with multicarpellate and apocarpous gynoecia that have been studied using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy. Lambertiflora and Mugideiriflora have numerous perianth parts in several series, as well as many stamens and many carpels borne on a short conical receptacle. Atlantocarpus has many carpels arranged spirally on an elongated receptacle. Perianth and stamens are not preserved in Atlantocarpus, but scars of two sizes at the base of the receptacle indicate the presence of several series of tepals and stamens. Phylogenetic assessment of the three new genera indicates close relationships with members of extant Austrobaileyales, which is also favoured by the apparently ascidiate carpels of Atlantocarpus. However, the phylogenetic signal is not strong and the fossils also share many features with magnoliid angiosperms. Fully secure resolution of their relationships is hampered by lack of information of critical floral features in the fossil material, the constellation of likely plesiomorphic characters that they exhibit, and inadequate knowledge of character homologies and character evolution among extant taxa. There is also the broader concern about whether phylogenetic patterns can be reliably inferred for the earliest phases of angiosperm evolution based solely on a depauperate assemblage of extant taxa given extensive extinction over the last 100 million years. The new genera add to growing evidence of diverse extinct angiosperms with multiparted flowers during the Early Cretaceous that have a variety of relationships to extant ANA-grade angiosperms and magnoliids.

Angiosperm mesofossils are described from the Lower Cretaceous Almargem Formation exposed near the village of Catefica, Portugal, and are thought to be of Aptian-early Albian age. The mesofossil assemblage from Catefica is diverse and, in addition to the angiosperms described here, also contains a rich assemblage of non-angiosperm fossils, including leafy axes of bryophytes and lycopsids, lycopsid and salvinialean megaspores, and sporangia, sori and leaf fragments of ferns. There are also twigs, cones, cone scales, seeds and sporangia of several kinds of conifers. Other seed plants include 11 species of chlamydospermous seeds and vegetative axes related to the BEG group (Bennettiales-Erdtmanithecales-Gnetales). In terms of the number of plant fragments identified, angiosperms are most abundant in the Catefica assemblage and account for more than half of all specimens. Angiosperms also dominate in number of species, but because the non-angiosperm fossils have not been studied in detail the total number of species in the flora is not yet established. Sixty-seven species of angiosperms are recognized. Angiosperm diversity is mainly at the level of non-eudicots, including ANA-grade angiosperms, Chloranthaceae and magnoliids. Remains of chloranthoid angiosperms are especially common, both in the number of specimens and in number of species recognized. About 40 % of the specimens, and more than 25 % of the species are chloranthoids. Remains of magnoliid angiosperms (Magnoliales, Laurales, Canellales, Piperales) are also prominent among the angiosperms. Eudicots are subordinate: only 3–4 % of all angiosperm specimens can be assigned confidently to eudicot angiosperms. Five new genera and six new species of angiosperms are established (Canrightia foveolata sp. nov., Elasmostemon paisii gen. et sp. nov., Endressistemon cateficensis gen. et sp. nov., Ibericarpus cuneiformis gen. et sp. nov., Proencistemon portugallicus gen. et sp. nov., Valvidistemon globiferus gen. et sp. nov.). Several other new taxa are also described, but not formally named.

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 meso-floras 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,andWelwitschia). 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.

Studies of Cretaceous age mesofossil floras – assemblages of small carbonaceous plant fossils isolated from poorly consolidated sediments – have provided a wealth of new insights into the early fos ...

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.

A new taxon, Skyttegaardia galtieri, is described based on microsporangiophores with Monosulcites/Cycadopites pollen isolated from clays collected at the Skyttegard locality, island of Bornholm, Denmark, which are of earliest Cretaceous (Berriasian) age. Each microsporangiophore consists of a short, massive proximal fertile stalk-like portion with a truncate base, and a long sterile distal extension. A cavity on each side of the median line of the stalk-like portion, partially encloses a sporangium that dehisces by a longitudinal slit. The long distal extension tapers to a slender point and is curved toward the inferred adaxial side. The extension is irregularly angular in cross-section and the cuticle is thick with deep stomatal pits. The organization of the microsporangiophore, the in situ pollen and stomatal features suggest relationship with extant Cycadales. However, in all extant and fossil cycads there are usually many more sporangia per microsporangiophore, typically in groups of two to five, and they are borne on the surface of the proximal stalk-like portion rather than embedded in its tissues. These differences preclude secure inclusion of Skyttegaardia in Cycadales and open the possibility that these microsporangiophores were produced by a group of extinct plants, the other parts of which remain to be identified. The thick cuticle and sunken stomata of Skyttegaardia, together with the embedded sporangia, suggest adaptation to water stress, which is also consistent with the xeromorphic traits seen among the leaf fragments in the Skyttegaard flora and the arid conditions inferred from geological–geochemical proxies.

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 unexpectedly high diversity of extinct angiosperms related to lineages that are now species poor, such as Austrobaileyales, Nymphaeales, and Chloranthaceae. Here we analyze Early Cretaceous fruits and seeds from Portugal that are related to eumagnoliid angiosperms and that are also important for understanding extinct diversity in early angiosperms. Methodology. The fossils were prepared by sieving in water; cleaned with HF, HCl, and water; and studied using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy. The systematic conclusion based on comparative studies was tested in a phylogenetic analysis. Pivotal results. We recognize a new group of angiosperms based on fruits and seeds united by features that are otherwise unusual among angiosperms. Two genera, Serialis and Riaselis, are established and 10 species described. Both have unilocular fruiting units formed from a single carpel. Serialis has fruits with two or more seeds, while fruits of Riaselis are always one seeded. In Serialis, seeds are permanently attached to each other and dispersed as a unit. Both genera have anatropous and mesotestal-endotestal seeds with a tiny embryo and a distinctive vasculature in the testa extending from the hilum to the chalaza and then also on the antiraphal side to the micropyle. The fossils are most similar to seeds of Magnoliales but also share some features with seeds of Austrobaileya. Conclusions. Serialis and Riaselis are the earliest fossils that can be assigned to the Magnoliales but are sufficiently different from those of all Magnoliales that they cannot be assigned to any extant family. Serialis and Riaselis provide further documentation of extensive extinct diversity among early angiosperms, and their abundance in the mesofossil floras suggests that they were common and widespread in early angiosperm communities.

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.

Premise of the Study: Exotestal seeds with characters that indicate relationship to extant Austrobaileyales and Nymphaeales are abundant in Early Cretaceous sediments from Portugal and eastern North America, but their variety and unique features provide evidence of extensive extinct diversity among early angiosperms. Methods: The fossils were extracted from Early Cretaceous sediments from Virginia and Maryland, United States, by sieving in water. After cleaning with HF, HCl and water, they were examined using SEM and SRXTM and compared to seeds of extant and fossil angiosperms. Key Results: A new genus, Tanispermum gen. nov., with four species (T. hopewellense sp. nov., T. marylandense sp. nov., T. drewriense sp. nov., and T. antiquum sp. nov.) is recognized. Relationship with extant Austrobaileyales and Nymphaeales is indicated by an exotesta of tall palisade sclerenchyma with undulate anticlinal walls forming a jigsaw puzzle-like surface pattern. However, seeds of Tanispermum differ from those of Austrobaileyales and Nymphaeales in their hemi-orthotropous–hemi-anatropous organization. Attempts to place Tanispermum in a phylogenetic context confront a variety of problems, including lack of information on other parts of these extinct plants. Conclusions: The discovery highlights the extent to which the morphology of extant angiosperms is not representative of the diversity that once existed among early-diverging members of the group. The relictual nature of extant taxa near the base of the angiosperm tree greatly complicates the reconstruction of ancestral character states and emphasizes the need for focused paleobotanical studies to elucidate the extinct diversity that existed early in angiosperm evolution.

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. Swiss Light Source at the Paul Scherrer Institute (European Union FP6 projects) [20130185, 20141047]; Swedish Research Council [2014-5228]; Portuguese Science Foundation (FCT) [UID/MAR/00350/2013]; CretaCarbo project [PTDC/CTE-GIX/113983/2009]

Early Cretaceous seeds from Virginia and Maryland, USA, part of a diverse complex of exotestal seeds in Early Cretaceous mesofossil floras from North America and Europe, provide new evidence of extensive extinction among early angiosperms. The seeds are assigned to a new genus, Nitaspermum, with six species: N. taylorii , N. hopewellense , N. crassum , N. virginiense , N. marylandense, and Nitaspermum sp. All seeds are small, anatropous, bitegmic, and exotestal, with the exotesta composed of a single layer of short, columnar sclerenchyma with strongly folded walls. Nitaspermum shows features of extant Austrobaileyales (Illiciaceae) and Nymphaeales but also critical differences precluding assignment to extant families. These discoveries are consistent with predictions from molecular phylogenetics that indicate the differentiation of Illiciaceae and Nymphaeales early in angiosperm evolution, but the diversity of such seeds underlines the extent to which the pattern of extant angiosperm diversity has been shaped by widespread extinction early in angiosperm evolution.

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.

© 2017 by The University of Chicago. All rights reserved. Premise of research. Numerous exquisitely preserved fossil floral structures recovered from Lower Cretaceous sediments in Portugal are invaluable for understanding the organization and structure of flowers at an early stage in angiosperm evolution. This study analyses three such flowers that add significantly to current knowledge of structural and systematic diversity among very early eumagnoliid angiosperms. Methodology. Fossil flowers were extracted from unconsolidated sedimentary rocks by sieving in water. Morphological and anatomical details were studied using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy. The phylogenetic position of the fossils was assessed using the available morphological data sets for extant taxa. Pivotal results. A new genus, Saportanthus, with three new species, S. brachystemon, S. dolichostemon, and S. parvus, is described from the Early Cretaceous of the Lusitanian Basin, western Portugal, based on coalified flowers. The flowers are small, actinomorphic, and structurally bisexual with semi-inferior ovary. Floral organs are apparently spirally arranged and variable in number. The perianth consists of six to eight tepals, and the androecium consists of five to 15 stamens. The stamens are almost sessile with basifixed, dithecate, and tetrasporangiate anthers. The thecae are separated by a massive connective. The four laterally placed pollen sacs protrude and dehisce by four laterally hinged valves that extend for the full length of the anther. Pollen grains are circular in polar view, trichotomocolpate or dicolpate, with a thin continuous tectum and granular infratectal layer. On the distal surface the tectum is psilate-punctate around the aperture but finely striate proximally with delicate ridges that form a distinctive fingerprint-like pattern. The gynoecium is semi-inferior and syncarpous with one to three locules and a single, apical, pendulous ovule in each locule. The stylar area is conical with one, two, or three short styles. The fruit is indehiscent and probably drupaceous, sometimes with only a single seed. Phylogenetic analyses based on the features of the fossil flowers place Saportanthus in Laurales, either as sister to core Laurales or as close to the clade comprising Lauraceae and Hernandiaceae. Conclusion. Flowers of Saportanthus possess a combination of characters that indicate a relationship to extant Laurales but that is unknown among extant or fossil members of the group . Saportanthus provides further evidence of extensive extinction in the early diversification of angiosperms, including in the early phases of evolution that ultimately gave rise to living groups.

Angiosperms (flowering plants) are the most diverse of all major lineages of land plants and the dominant autotrophs in most terrestrial ecosystems. Their evolutionary and ecological appearance is therefore of considerable interest and has significant implications for understanding patterns of diversification in other lineages, including insects and other animals. More than half a century ago, influential reviews showed that while angiosperms are richly represented in sediments of Late Cretaceous and younger ages, there are no reliable records of angiosperms from pre-Cretaceous rocks. The extensive new macrofossil, mesofossil, and microfossil data that have accumulated since have confirmed and reinforced this pattern. Recently, however, molecular dating methods have raised the possibility that angiosperms may have existed much earlier, and there have been scattered reports of putative angiosperms from Triassic and Jurassic rocks. Critical assessment of these reports shows that, so far, none provide unequivocal evidence of pre-Cretaceous angiosperms. Angiosperms may ultimately be recognized from Jurassic or earlier rocks, but credible palaeobotanical evidence will require unambiguous documentation of the diagnostic structural features that separate angiosperms from other groups of extant and extinct seed plants. Molecular dating has suggested that angiosperms existed earlier than the Late Cretaceous. Scattered fossil evidence for Triassic or Jurassic angiosperms exists but this Review concludes that the case remains unproven at best.

A new Early Cretaceous flower, Kenilanthus marylandensis, is described from the fossil plant bearing sequence exposed in early-middle Albian Potomac Group sediments at the Kenilworth (Bladensburg) locality, Maryland, USA. The flower is small, actinomorphic, pentamerous, and isomerous, and contains both pistillate and staminate parts. The receptacle is slightly dome-shaped and bears one whorl of five tepals, with a possible additional whorl toward the outside, ten stamens in two whorls of five, and one whorl of five free carpels. Stamens have elongate, tetrasporangiate, dithecate anthers that arc slightly inwards towards the centre of the flower. Thecae protrude and are oriented outwards. Pollen grains are small, tricolpate and reticulate with a graded, heterobrochate reticulum and segmented, spiny muri. Carpels are elongate with abundant stomata on the outer surface, and each carpel has a broad oblique base. Ovules are numerous in each carpel and are borne on two marginal placentae that extend alo...

Eudicots, the most diverse of the three major clades of living angiosperms, are first recognized in the latest Barremian–earliest Aptian. All Early Cretaceous forms appear to be related to species-poor lineages that diverged before the rise of core eudicots, which today comprise more than 70% of angiosperm species. Here, we report the discovery of a well-preserved flower, Caliciflora mauldinensis, from the earliest Late Cretaceous, with unequivocal core eudicot features, including five sepals, five petals and two whorls of stamens borne on the rim of a floral cup containing three free carpels. Pollen is tricolporate. Carpels mature into follicular fruitlets. This character combination suggests a phylogenetic position among rosids, but more specific assignment is precluded by complex patterns of character evolution among the very large number of potentially relevant extant taxa. The whorled floral organization is consistent with ideas that this stable pattern evolved early and was a prerequisite for more integrated patterns of floral architecture that evolved later. However, limited floral synorganization in Caliciflora and all earlier eudicot flowers recognized so far, calls into question hypotheses that substantial diversification of core eudicots had already occurred by the end of the Early Cretaceous. VR 2014-5228: Blomväxternas tidiga historia och vegetationsutveckling under krittiden

Flowers of extant Quintinia are described in detail on the basis of field observations and serial microtome sections and compared with flowers of the Late Cretaceous Silvianthemum suecicum and Bertilanthus scanicus on the basis of new analyses of the fossil material. The analyses of both extant and fossil material also include synchrotron-based X-ray tomographic microscopy. The study shows that Quintinia and Silvianthemum/Bertilanthus have more features in common than previously recognized and strongly reinforces their earlier assumed close relationships. Among important characters linking the three genera are similar secretory hairs on the floral surface and pedicel; short sepals; free, quincuncial petals; broad anthers with small pollen sacs; 4-aperturate pollen (in Silvianthemum and Quintinia); postgenital union of the 3–4 apocarpous styles (in Silvianthemum and Quintinia); connection of the apocarpous carpel parts with the floral base; downward tapering ovary and locule(s); placentation on incomplete ...

Five species of seeds are described in four new genera that are broadly similar to seeds of the Bennettitales, Erdtmanithecales, and Gnetales (Tomcatia taylorii, Tomcatia sp., Cattomia trapezoides, Acanthocatia virginiensis, Quadrispermum parvum). The material is based on numerous charcoalified and lignitic specimens recovered from Early Cretaceous mesofossil floras in Portugal (Arazede, Buarcos, Catefica, Famalicao, Torres Vedras, Vale de Agua) and eastern North America (Puddledock). The seeds all have a prominent seed envelope that encloses a thin integument and the lower part of the long, slender micropylar tube. Seeds of all four genera are distinguished from previously described seeds of this kind in having a strongly four-angled seed envelope with distinct transverse ridges that create a rugulate seed surface. The seed envelope is composed of sclerenchyma cells toward the inside and an outer zone of nonlignified cells toward the outside. The outer zone is often composed of distinctive and prominent ...

Monetianthus mirus gen. et sp. nov. is described based on a single coalified flower from the Early Cretaceous (Late Aptian‐Early Albian) Vale de Agua locality, western Portugal. The flower is actinomorphic and probably bisexual, with a perianth of nine or 10 tepals, an androecium of 20 stamens, and a syncarpous gynoecium with a partly inferior ovary of 12 carpels arranged radially around a central column. Phyllotaxis of tepals and stamens is uncertain. Nondestructive synchrotron radiation x‐ray tomographic microscopy of internal structures documents laminar placentation with around six anatropous and ascending ovules in each locule. Comparison of Monetianthus with living plants indicates a clear relationship to extant Nymphaeales in particular with the Barclaya and Nymphaeoideae clade. Monetianthus thus provides evidence of crown group Nymphaeales, and probably crown group Nymphaeaceae, at a very early stage in the initial diversification of flowering plants.

Four new genera and six new species of fossil seed (Buarcospermum tetragonium, Lignierispermum maroneae, Lobospermum glabrum, L. rugosum, L. stampanonii, Rugonella trigonospermum) are described from five Early Cretaceous mesofossil floras from Portugal and eastern North America. The four genera are distinguished by differences in size, shape, and details of seed anatomy, but all are unusual in having an outer seed envelope with a distinctive anatomical structure that surrounds the nucellus and the integument. The integument is extended apically into a long, narrow micropylar tube. The four new genera are part of a diverse, but previously unrecognized, complex of extinct plants that was widespread in Early Cretaceous vegetation and that coexisted in similar habitats with early angiosperms. The distinctive structure of these seeds, and the strong similarities to other fossil seeds (Ephedra, Ephedripites, Erdtmanispermum, Raunsgaardispermum, and some Bennettitales) already known from the Early Cretaceous, suggests that this newly recognized complex of extinct plants, together with Bennettitales, Erdtmanithecales, and Gnetales (the BEG group), is phylogenetically closely related.

A charcoalified fossil flower, Potomacanthus lobatus gen. et sp. nov., is described from the Early Cretaceous (Early to Middle Albian) Puddledock locality, Virginia, USA. Internal floral structure was studied using nondestructive synchrotron-radiation x-ray tomographic microscopy (SRXTM). The flower is bisexual and trimerous. The perianth consists of two whorls of tepals. The androecium has two whorls of fertile stamens. Anthers open by two distally hinged valves. The gynoecium consists of a single carpel that is plicate in the style and ascidiate in the ovary and contains a single pendant ovule. The fossil flower shares many similarities with flowers of extant Lauraceae and is unlike flowers of other families of Laurales. However, the fossil flower also differs in detail from all extant or fossil Lauraceae, particularly in configuration of the androecium. The new taxon, together with previously described but more fragmentary material from the Puddledock locality, provides the earliest fossil record of plants more closely related to Lauraceae than to any other extant family. It reveals several derived morphological characters that are potential synapomorphies among extant representatives of the family Lauraceae and contributes to the growing evidence for an early diversification of Laurales before the end of the Early Cretaceous.

Five new taxa with affinities to extant lineages that diverged at an early stage from the main line of eudicot evolution are established from the Early Cretaceous (late Aptian or early Albian) Vale de Agua locality, Portugal. Staminate flowers of Lusistemon striatus and pistillate flowers of Lusicarpus planatus are unisexual without rudiments of the opposite gender. They are linked by the association of an unusual pollen type found in situ in the stamens and adhering to the stigmatic surface. The staminate flower, Lusistemon striatus, is composed of six stamens subtended by small perianth parts. The arrangement of the stamens is difficult to ascertain, but their variable sizes suggests a spiral arrangement. Pollen found in situ is tricolpate and striate with densely‐spaced, sparsely diverging and anastomosing muri that are aligned more or less parallel to the polar axis. The muri have a conspicuous supratectal ornamentation of fine transverse ridges. The granular infratectal layer forms an indistinct inte...

The rapid diversification of angiosperms through the Early Cretaceous period, between about 130-100 million years ago, initiated fundamental changes in the composition of terrestrial vegetation and is increasingly well understood on the basis of a wealth of palaeobotanical discoveries over the past four decades and their integration with improved knowledge of living angiosperms. Prevailing hypotheses, based on evidence both from living and from fossil plants, emphasize that the earliest angiosperms were plants of small stature with rapid life cycles that exploited disturbed habitats in open, or perhaps understorey, conditions. However, direct palaeontogical data relevant to understanding the seed biology and germination ecology of Early Cretaceous angiosperms are sparse. Here we report the discovery of embryos and their associated nutrient storage tissues in exceptionally well-preserved angiosperm seeds from the Early Cretaceous. Synchrotron radiation X-ray tomographic microscopy of the fossil embryos from many taxa reveals that all were tiny at the time of dispersal. These results support hypotheses based on extant plants that tiny embryos and seed dormancy are basic for angiosperms as a whole. The minute size of the fossil embryos, and the modest nutrient storage tissues dictated by the overall small seed size, is also consistent with the interpretation that many early angiosperms were opportunistic, early successional colonizers of disturbance-prone habitats.

Canrightiopsis with three species (C. intermedia, C. crassitesta, C. dinisii) is described from the Early Cretaceous of Portugal based on small, one-seeded berries. The fruits are derived from bisexual flowers with three stamens borne on one side of the ovary. There are no traces of a perianth. Pollen is of the Clavatipollenites-type, monocolpate, semitectate, reticulate-columellate with heterobrochate reticulum and muri with beaded supratectal ornamentation. The ovary is unilocular with a single pendant, orthotropous and bitegmic ovule. The seed is endotestal. The endotesta consists of one layer of palisade-shaped crystal cells with fibrous infillings. The fruit wall has resin bodies or cavities from presumed ethereal oil cells sometimes seen as stomata-like structures on the fruit surface. A phylogenetic analysis resolves Canrightiopsis as a close relative of extant Chloranthaceae, particularly close to extant Chloranthus and Sarcandra. All three taxa share the one-sided position of the stamens on the ovary. An evolutionary sequence from fossil Canrightia to fossil Canrightiopsis and extant Chloranthus and Sarcandra is suggested by loss of perianth, reduction in number of ovules and stamens and displacement of stamens to one side of the ovary. Canrightiopsis also shares several critical features with extant Ascarina including monoaperturate pollen and beaded supratectal ornamentation of the pollen wall. Swiss Light Source (European Union) [20110963, 20130185]; Swedish Research Council [621-2011-5431]; CretaCarbo project [PTDC/CTE-GIX/113983/2009] info:eu-repo/semantics/publishedVersion

New Normapolles reproductive structures are described from two Late Cretaceous localities, Mira and Esgueira (Olho de Agua), in the Beira Litoral region of western Portugal. They are assigned to a new genus, Endressianthus, containing two new species, Endressianthus miraensis and Endressianthus foveocarpus. The new genus is based on several small inflorescence fragments with cymose branching and dichasial inflorescence subunits bearing either pistillate or staminate flowers, as well as on numerous isolated stamens and fruits. The pistillate flowers have an inferior ovary and minute, acicular tepals. The gynoecium is bicarpellate and syncarpous. In the fruiting stage, the stigmatic area on top of the ovary is seen as an elongate slit that is covered by stiff simple trichomes. Fruits are nuts with one or two locules and one or two seeds. The staminate flowers consist of four stamens with short filaments and elongate tetrasporangiate anthers and apparently a whorl of small, thornlike tepals. Typically, only ...

A new species of megaspores, Arcellites punctatus sp. nov. and associated microspores, are described from the Early Cretaceous Torres Vedras, Catefica and Buarcos localities in Portugal. The new taxon is most abundant in the Torres Vedras plant assemblages where it co-occurs with several other types of megaspores, remains of aquatic and terrestrial angiosperms as well as other plant fossils. The megaspore body is smooth without appendages, finely perforated and with a rugose surface pattern. High resolution synchrotron radiation X-ray tomographic microscopy (SRXTM) analysis of the megaspore wall shows a three-layered structure. The outer layer is punctate-perforate. Perforations are densely spaced in the valleys between the ridges, while they are more scattered or lacking on the top of the ridges. The middle layer is granularfibrous and of uneven thickness causing the rugose surface pattern. The inner layer is evenly thin and solid. The outer layer of the megaspore body continues into the elongated, six-parted and inverted cone-shaped acrolamella or neck. Lateral margins of acrolamella segments are laminar and crenulate. Microspores occur attached to the acrolamella of all specimens studied in scanning electon microscopy (SEM) and SRXTM. In general morphology, the megaspores are closely similar to megaspores of Arcellites rugosus from Canada that also lack body appendages, but the Portuguese megaspores are distinguished by their distinct punctate-perforate megaspore wall structure.

Journal of paleontology, 88 (4), ISSN:0022-3360, ISSN:1937-2337

Phylogenetic analyses have identified the water lilies (Nymphaeales: Cabombaceae and Nymphaeaceae), together with four other small groups of flowering plants (the ‘ANITA clades’: Amborellaceae, Illiciales, Trimeniaceae, Austrobaileyaceae), as the first diverging lineages from the main branch of the angiosperm phylogenetic tree1,2,3,4, but evidence of these groups in the earliest phases of the angiosperm fossil record has remained elusive. Here we report the earliest unequivocal evidence, based on fossil floral structures and associated pollen, of fossil plants related to members of the ANITA clades. This extends the history of the water lilies (Nymphaeales) back to the Early Cretaceous (125–115 million years) and into the oldest fossil assemblages that contain unequivocal angiosperm stamens and carpels. This discovery adds to the growing congruence between results from molecular-based analyses of relationships among angiosperms and the palaeobotanical record. It is also consistent with previous observations that the flowers of early angiosperms were generally very small5 compared with those of their living relatives.

A survey of five mesofossil floras from the Early Cretaceous (Barremian or Aptian) of Portugal documents considerable taxonomic and structural diversity among early angiosperms. Currently ca. 140–150 different angiosperm taxa have been identified in these floras, of which ca. 85% are taxa at the magnoliid grade—perhaps also with some basal monocots. Evidence is beginning to emerge that those lineages identified as basal among angiosperms in phylogenetic analyses (recently referred to as the ANITA grade of basal magnoliids, including Amborellaceae, Nymphaeales, Illiciales, Trimeniaceae, and Austrobaileyaceae) were already well represented in the Early Cretaceous, at which time they were probably more diverse than they are today. Many of the fossil angiosperms from the Portuguese floras cannot be assigned to any existing group, and there is clear evidence of significant extinction.

Seeds and fruits of Early Cretaceous (Barremian-Aptian) angiosperms from the Famalicão locality in Portugal were analyzed to establish seed and fruit size (volume) distributions and to infer the proportion of animal-dispersed fruits. On the basis of a sample of 106 angiosperm fruit and seed taxa, the average seed size was 0.78 mm3 (range 0.02-6.86 mm3), whereas the average fruit size was 2.06 mm3 (range 0.12-8.34 mm3). Variation in seed size among taxa is smaller than in modern plant communities, but within-taxon variation is similar to that known for extant plants. No significant difference in the size of "fleshy" versus other fruits was observed. The proportion of fleshy fruits was 24.5%. This high figure was surprising and indicates that the significance of animal dispersal during an early stage in angiosperm evolution has been underestimated. We suggest that reptiles and multituberculates, and perhaps other mammals and birds as well, were the likely seed dispersers and that the early angiosperms from Famalicão probably were herbs or small shrubs that inhabited a semiopen coniferous woodland.

Distinctive monocolpate and reticulate-acolumellate pollen grains with a coarse, loosely attached reticulum have long been known as a conspicuous element of many palynological assemblages from the Early and mid-Cretaceous. These grains are now described in situ in staminate structures and on the surface of pistillate organs from two Early Cretaceous (Barremian or Aptian) mesofloras from Portugal (Vale de Agua and Buarcos). Staminate organs include a staminate axis with spirally arranged stamens and many isolated stamens. Stamens consist of a short filament, a dithecate, tetrasporangiate anther, and a short apical extension of the connective. Anther dehiscence is extrorse by longitudinal slits and in situ pollen is monocolpate, semi-tectate with a coarse, loosely attached reticulum composed of narrow muri with a spiny ornamentation. The infratectal layer of the pollen wall is thin, granular, and lacking columellae; and the foot layer is distinct. The endexine is thin, except under the aperture where it is ...

A new angiosperm genus, Anacostia, with four species (A. marylandensis, A. virginiensis, A. portugallica, A. teixeirae) is described from Early Cretaceous floras in North America and Portugal. Anacostia comprises small, unilocular and one‐seeded fruiting units (each derived from a single carpel) with a sessile and indistinct stigmatic area. There are indications that a fleshy layer was originally present in the fruit wall. The seeds are anatropous, testai, and apparently derived from a bitegmic ovule. Pollen grains adhering to the stigmatic area and fruit wall are monoaperturate and trichotomocolpate or monocolpate. The pollen tectum is distinctly graded, reticulate to foveolate with the size of lumina decreasing towards the aperture and towards the proximal pole. The four species show substantial similarities in morphology, and in the anatomy of fruit, seed, and pollen, but can be distinguished by size and shape, as well as details of the fruit and seed wall. The Anacostia fruiting units are similar in s...

A new pollen organ, Eucommiitheca hirsuta, containing Eucommiidites pollen grains is described from the Early Cretaceous of Portugal. The material comprises dispersed microsporangiate units and fragments of axes bearing microsporangiate units in an opposite and decussate arrangement. Each microsporangiate unit consists of a slightly angular to rounded peltate scale attached centrally to a short stalk, and with whorls of sporangia around the distal part of the stalk. Sporangia are stalked and free, with longitudinal dehiscence, and contain pollen grains similar to the characteristic dispersed pollen genus Eucommiidites. Eucommiitheca is comparable to Erdtmanitheca, another Cretaceous pollen organ containing Eucommiidites pollen, in the peltate nature of the microsporangiate units, but microsporangiate units in Erdtmanitheca are arranged in dense heads and sporangia are elongate. The opposite and decussate arrangement of the microsporangiate units in Eucommiitheca is in accordance with the possible...

The major diversification of flowering plants (angiosperms) in the Early Cretaceous, between about 130 and 90 million years ago, initiated fundamental changes in terrestrial ecosystems and set in motion processes that generated most of the extant plant diversity. New palaeobotanical discoveries, combined with recent phylogenetic analyses of morphological and molecular data, have clarified the initial phases of this radiation and changed our perspective on early angiosperm evolution, though important issues remain unresolved.

A new genus and species of fossil flowers, Bertilanthus scanicus, is described from the Late Cretaceous of southern Sweden. The flowers of B. scanicus are actinomorphic and bisexual with an inferior ovary. Perianth and androecium are pentamerous. The sepals are small and free, and calyx aestivation is apert; petals are larger, and aestivation of corolla is imbricate. The androecium consists of a single whorl of stamens opposite the petals. The anthers are dithecate, tetrasporangiate, sagittate, and dorsifixed. Pollen observed in the flower is minute and oblate to spheroidal with three colpi and a tectate-punctate pollen wall. The gynoecium is formed from two carpels, and there are two free and stout styles. The epidermal cells of the styles are palisade shaped and form a distinct radiating pattern. The ovary is unilocular with numerous anatropous ovules borne on two intruding parietal placentae. There is a distinct five-parted nectary disk inserted between perianth and styles. The fruit was probably dry a...

We describe a new well-preserved fossil flower, Virginianthus calycanthoides gen. et sp. nov., from the Early Cretaceous (Early or Middle Albian) of Virginia. The flower is multipartite and has a distinct, deep floral cup. The perianth and androecium are borne on the rim of the floral cup and arranged in several crowded series. Reconstruction of the flower indicates that the perianth is composed of about 12 closely spaced tepals with apically directed hairs on the abaxial surface. The androecium consists of approximately 30-40 closely spaced, sessile stamens. The anthers are dithecate and tetrasporangiate, with the pollen sacs borne toward the abaxial surface. Dehiscence is extrorse through laterally hinged valves. Pollen grains are monocolpate and reticulate and resemble the previously described pollen species Clavatipollenites minutus Brenner. Sterile structures in the transition zone between androecium and gynoecium are interpreted as inner staminodes. The gynoecium is composed of approximately 18-26 c...

Two new species of platanoid reproductive structure are described from the Bull Mountain locality in the Patapsco Formation (Potomac Group) of northeastern Maryland, USA. Pistillate inflorescences and infructescences ( Platanocarpus elkneckensis sp. nov.) consist of flowers and fruits in sessile globose heads that are borne on an elongate axis. Individual pistillate flowers consist of five free carpels surrounded by prominent tepals. Staminate inflorescences, flowers and isolated stamens are assigned to Hamatia elkneckensis gen. et sp. nov. Staminate flowers are borne in a globose head with a small number of stamens (five?) per flower. Stamens consist of very short filaments, long anthers with strongly valvate dehiscence and an apically expanded connective. The connective expansion is frequently very well-developed, hook-like and extends down the ventral surface of the stamen. Anthers contain small, tricolporate, reticulate pollen. Association evidence, similarity of inflorescence structure and the occurrence of Hamatia -type pollen on flowers, carpels and fruits of Platanocarpus elkneckensis suggests that the staminate and pistillate material was produced by a single species of plant. The “ Hamatia -plant” provides further evidence of pentamerous floral structure in mid-Cretaceous platanoids and documents the occurrence of unequivocal tricolporate pollen in the platanoid complex.

The global environment during the earliest phases of angiosperm diversification was radically different from that of today. The geography and distribution of continents was unlike that of our modern world and the Cretaceous was also a time of generally higher sea levels and higher global temperatures. There were low thermal gradients from the equator to the poles (DeConto et al ., 2000a; Gale, 2000; MacLeod et al ., 2000), patterns of rainfall were quite different (Parrish, 1987) and there is no unequivocal evidence of polar ice caps during the Cretaceous and Early Cenozoic (Gale, 2000). The Cretaceous is often considered the classic example of ‘greenhouse’ or ‘supergreenhouse’ conditions in Earth history. These unusual conditions compared with today profoundly influenced the ecology and evolution of life on land as angiosperms underwent their initial radiation and then diversified to become the dominant primary producers in most terrestrial ecosystems. Our modern world provides a poor analogue for the environmental backdrop against which more than half of the evolutionary history of angiosperms unfolded. In this chapter we provide a brief overview of changes in palaeogeography and palaeoclimate through the Cretaceous period, a time interval of 80 million years (Figure 3.1). More detailed accounts can be found elsewhere (e.g. Skelton, 2003b). The aim here is to provide a short summary that places patterns of early angiosperm evolution in their environmental context. Palaeogeography During the later Palaeozoic and Triassic a single supercontinent, Pangaea, was formed through the coalescence of all pre-existing major continental masses. The southern part, Gondwana, consisted of South America, Africa, Apulia (present-day Italy), Arabia, Australia, New Zealand, Antarctica, India, and Madagascar. The northern part, Laurasia, consisted of many smaller and larger continents with North America, Greenland, Europe, Iberia, Siberia, Kazakhstan, Kolyma and China as its main components. Pangaea persisted into the early Mesozoic, but began to break up during the Triassic and Jurassic through a series of processes that continued into the Cretaceous (Figures 3.2–3.5) (Smith et al ., 1981; Scotese et al ., 1988).

This chapter provides an overview of the main patterns of structural diversification in angiosperm flowers as inferred from the occurrence of floral features in the fossil record in the context of phylogenetic analyses of angiosperm relationships (Chapter 7). The systematic chapters (Chapters 8–15) provide descriptions of the individual fossils and cite the relevant literature. Here we focus on broader patterns, the appearance of major structural novelties and, where possible, what these imply about floral innovation among angiosperms as a whole. In part these large-scale patterns in the evolution of floral structure reflect the successive diversification of different lineages of angiosperms at different times in the past. The consequences of floral innovation for angiosperm pollination and dispersal biology are considered in Chapters 17 and 18. Aspects of the diversification of reproductive structure in specific angiosperm lineages are addressed in Chapter 20. Building on earlier work by Brenner (1963), Muller (1970) and others, studies in the 1970s on early angiosperms from the Potomac Group of eastern North America were the first to demonstrate a coordinated increase in the diversity and ‘advancement’ of pollen and leaves through the Early and mid-Cretaceous (Doyle and Hickey, 1976; Hickey and Doyle, 1977; Hickey, 1978). This work confirmed that monoaperturate angiosperm pollen appeared first in the fossil record, an observation that was (and remains) consistent with phylogenetic concepts based on extant plants. A parallel increase in the structural complexity of fossil angiosperm leaves was also broadly consistent with interpretations of the evolution of leaf architecture among extant taxa (Hickey and Wolfe, 1975; Doyle and Hickey, 1976; Hickey and Doyle, 1977).