| 1. |
- Wang, Li-San, et al.
(författare)
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Rarity of the Alzheimer Disease-Protective APP A673T Variant in the United States.
- 2015
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Ingår i: JAMA neurology. - : American Medical Association (AMA). - 2168-6157 .- 2168-6149. ; 72:2
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Tidskriftsartikel (refereegranskat)abstract
- Recently, a rare variant in the amyloid precursor protein gene (APP) was described in a population from Iceland. This variant, in which alanine is replaced by threonine at position 673 (A673T), appears to protect against late-onset Alzheimer disease (AD). We evaluated the frequency of this variant in AD cases and cognitively normal controls to determine whether this variant will significantly contribute to risk assessment in individuals in the United States.
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| 2. |
- Escott-Price, Valentina, et al.
(författare)
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Gene-Wide Analysis Detects Two New Susceptibility Genes for Alzheimer's Disease
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:6, s. e94661-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Alzheimer's disease is a common debilitating dementia with known heritability, for which 20 late onset susceptibility loci have been identified, but more remain to be discovered. This study sought to identify new susceptibility genes, using an alternative gene-wide analytical approach which tests for patterns of association within genes, in the powerful genome-wide association dataset of the International Genomics of Alzheimer's Project Consortium, comprising over 7 m genotypes from 25,580 Alzheimer's cases and 48,466 controls. Principal Findings: In addition to earlier reported genes, we detected genome-wide significant loci on chromosomes 8 (TP53INP1, p = 1.4x10(-6)) and 14 (IGHV1-67 p = 7.9x10(-8)) which indexed novel susceptibility loci. Significance: The additional genes identified in this study, have an array of functions previously implicated in Alzheimer's disease, including aspects of energy metabolism, protein degradation and the immune system and add further weight to these pathways as potential therapeutic targets in Alzheimer's disease.
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| 3. |
- Jones, Lesley, et al.
(författare)
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Convergent genetic and expression data implicate immunity in Alzheimer's disease
- 2015
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Ingår i: Alzheimer's & Dementia. - : Wiley. - 1552-5260 .- 1552-5279. ; 11:6, s. 658-671
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Tidskriftsartikel (refereegranskat)abstract
- Background: Late-onset Alzheimer's disease (AD) is heritable with 20 genes showing genome-wide association in the International Genomics of Alzheimer's Project (IGAP). To identify the biology underlying the disease, we extended these genetic data in a pathway analysis. Methods: The ALIGATOR and GSEA algorithms were used in the IGAP data to identify associated functional pathways and correlated gene expression networks in human brain. Results: ALIGATOR identified an excess of curated biological pathways showing enrichment of association. Enriched areas of biology included the immune response (P = 3.27 X 10(-12) after multiple testing correction for pathways), regulation of endocytosis (P = 1.31 X 10(-11)), cholesterol transport (P = 2.96 X 10(-9)), and proteasome-ubiquitin activity (P = 1.34 X 10(-6)). Correlated gene expression analysis identified four significant network modules, all related to the immune response (corrected P = .002-.05). Conclusions: The immime response, regulation of endocytosis, cholesterol transport, and protein ubiquitination represent prime targets for AD therapeutics.
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| 4. |
- Abolfathi, Bela, et al.
(författare)
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The Fourteenth Data Release of the Sloan Digital Sky Survey : First Spectroscopic Data from the Extended Baryon Oscillation Spectroscopic Survey and from the Second Phase of the Apache Point Observatory Galactic Evolution Experiment
- 2018
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Ingår i: Astrophysical Journal Supplement Series. - : IOP Publishing Ltd. - 0067-0049 .- 1538-4365. ; 235:2
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Tidskriftsartikel (refereegranskat)abstract
- The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since 2014 July. This paper describes the second data release from this phase, and the 14th from SDSS overall (making this Data Release Fourteen or DR14). This release makes the data taken by SDSS-IV in its first two years of operation (2014-2016 July) public. Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey; the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data-driven machine-learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from the SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS web site (www.sdss.org) has been updated for this release and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020 and will be followed by SDSS-V.
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| 5. |
- Blanton, Michael R., et al.
(författare)
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Sloan Digital Sky Survey IV : Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
- 2017
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Ingår i: Astronomical Journal. - : IOP Publishing Ltd. - 0004-6256 .- 1538-3881. ; 154:1
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Tidskriftsartikel (refereegranskat)abstract
- We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and. high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median z similar to 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between z similar to 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs. and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the. Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July.
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| 6. |
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The Seventeenth Data Release of the Sloan Digital Sky Surveys : Complete Release of MaNGA, MaStar, and APOGEE-2 Data
- 2022
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Ingår i: Astrophysical Journal Supplement Series. - : Institute of Physics (IOP). - 0067-0049 .- 1538-4365. ; 259:2
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Tidskriftsartikel (refereegranskat)abstract
- This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys.
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| 7. |
- Crane, Peter Robert, et al.
(författare)
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Water lilies, loss of woodiness, and model systems
- 2020
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Ingår i: Proceedings of the National Academy of Sciences. ; 117, s. 9674-9676
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Tidskriftsartikel (refereegranskat)abstract
- The delicate necklace of threaded petals from the tomb of Rameses II, mid-nineteenth century glasshouses built for the newly discovered Victoria amazonica, and Monet’s giant canvases in the Mus´ee de l’Orangerie all testify to a deep human attraction to waterlilies: beguiling plants with showy flowers that seem toarise nymph-like out of the mud. Like orchids, cacti, succulents, and carnivorous plants, water lilies have a dedicated band of horticulturalists devoted to growing and exploring their endless variety. The late nineteenth century craze for water lilies that attracted Monet was fueled by one such enthusiast, Joseph Bory Latour-Marliac, who developed hardy waterlily cultivars with dazzling new flower colors ranging from “delicate yellow to fuscia and deep red.” Nymphaea thermarum, the focus of the recent paper by Povilus et al., is another unusual water lily variant. The smallest water lily known, N. thermarum was discovered and described in the late 1980s. Endemic to hot spring lakes in the Albertine Rift Valley of Rwanda, now, just a few decades after its discovery,it appears to be extinct in the wild.
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| 8. |
- Friis, Else Marie, et al.
(författare)
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Catanthus, an Extinct Magnoliid Flower from the Early Cretaceous of Portugal
- 2021
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Ingår i: International journal of plant sciences. - : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 182, s. 28-45
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Tidskriftsartikel (refereegranskat)abstract
- 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 + Magnoliales or Canellales + 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.
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| 9. |
- Friis, Else Marie, et al.
(författare)
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Chlamydospermous seeds document the diversity andabundance of extinct gnetalean relatives in Early Cretaceous vegetation
- 2019
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Ingår i: International journal of plant sciences. - Chicago : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 180, s. 643-666
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- Friis, Else Marie, et al.
(författare)
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Early and Mid-Cretaceous Aristolochiaceous Seeds from Portugal and Eastern North America
- 2022
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Ingår i: International journal of plant sciences. - Chicago : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 183:7, s. 587-603
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Tidskriftsartikel (refereegranskat)abstract
- Premise of research. The fossil record of Aristolochiaceae (Piperales, magnoliids) is sparse, particularly from Cretaceous strata. Fossil seeds from the Early and mid-Cretaceous of Portugal and North America provide the earliest unequivocal documentation of the group.Methodology. Detailed morphological and anatomical investigations of the fossil aristolochiaceous seeds were carried out using SEM and synchrotron radiation X-ray tomographic microscopy (SRXTM). Comparison with other seeds, extinct as well as extant, was based on published data and SRXTM analyses.Pivotal results. Two new genera and two new species, Aristospermum huberi and Siratospermum mauldinense, are described based on fossil seeds from the Early and mid-Cretaceous of Portugal and North America. The seeds are anatropous and bitegmic, with the micropyle formed by the inner integument. The testa consists of an exotesta of varied thickness and an endotesta of crystalliferous cells. The tegmen is three cell layers thick and consists of an outermost layer of longitudinally aligned fibers, a middle layer of transversely aligned fibers perpendicular to the longitudinal fibers, and an inner layer of thin-walled cuboidal cells. In most seeds the exotesta is abraded, exposing the crystalliferous cells of the endotesta. Among extant plants, a similar seed coat with a crystalliferous endotesta and crossing fibers in the tegmen is unique to Aristolochiaceae.Conclusion. The unique seed coat allows Aristospermum and Siratospermum to be assigned confidently to the lineage that today includes extant Aristolochiaceae. Aristospermum and Siratospermum provide the first unequivocal documentation of the Aristolochiaceae lineage of the Piperales during the Early Cretaceous diversification of angiosperms.
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| 11. |
- Friis, Else Marie, et al.
(författare)
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Early flowers of primuloid Ericales from the Late Cretaceous of Portugal and their ecological and phytogeographic implications
- 2021
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Ingår i: Fossil Imprint. - Prague : Národní muzeum. - 2533-4050 .- 2533-4069. ; 77:2, s. 214-230
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Tidskriftsartikel (refereegranskat)abstract
- A distinctive feature of the major eudicot diversification that occurred through the Late Cretaceous is the unequivocal presence of Cornales and diverse Ericales. Here we describe well-preserved fossil flowers from the Mira locality in western Portugal, of Campanian-Maastrichtian age, that we assign to a new extinct genus of Ericales with two new species; Miranthus elegans gen. et sp. nov. and Miranthus kvacekii sp. nov. The fossil flowers are pedicellate, structurally bisexual, actinomorphic, pentamerous and isomerous, with five narrowly triangular persistent calyx lobes, a five-lobed corolla, five antepetalous stamens, five staminodes alternating with the petals and a semi-inferior, unilocular ovary. The ovary consists of five carpels and has a raised nectariferous ring with stomata-like openings above the insertion of the perianth, and a long five-angled style. A key feature, which confirms a relationship with Primulaceae s. l., is the free, central dome-shaped placenta that bears numerous, densely spaced ovules. The ovary matures into a capsule containing many, minute, reticulate seeds. Flowers of Miranthus are especially similar to those of extant Samolus, a genus of about twelve species that is sister group to other genera of subfamily Theophrastoideae and that has a disjunct distribution mainly in the Southern Hemisphere. Miranthus also appears to have grown in environments influenced by marine conditions, an ecological preference also seen in Samolus. Miranthus expands the diversity of Ericales known from the Late Cretaceous, and together with previously described fossils provides further evidence that the diversification of Ericales was already underway by the Campanian-Maastrichtian stages of the Late Cretaceous.
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| 12. |
- Friis, Else Marie, et al.
(författare)
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Exceptional preservation of tiny embryos documents seed dormancy in early angiosperms
- 2015
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 528, s. 551-554
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 13. |
- Friis, Else Marie, et al.
(författare)
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Extinct diversity among Early Cretaceous angiosperms: mesofossilevidence of early Magnoliales from Portugal
- 2019
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Ingår i: International Journal of Plant Sciences. - Chicago : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 180, s. 93-127
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 14. |
- Friis, Else Marie, et al.
(författare)
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Extinct seed plant diversity in the Early Cretaceous: An enigmatic new microsporangiate fossil with Decussosporites pollen in situ
- 2022
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Ingår i: Review of Palaeobotany and Palynology. - Amsterdam : Elsevier. - 0034-6667 .- 1879-0615. ; 304, s. 104716-104716
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Tidskriftsartikel (refereegranskat)abstract
- A new microsporangiate cone, Renbernia zhoui, is described from the mesofossil flora extracted from exposures ofthe 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.
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| 15. |
- Friis, Else Marie, et al.
(författare)
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Extinct taxa of exotestal seeds close toAustrobaileyales and Nymphaeales from the Early Cretaceous of Portugal
- 2018
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Ingår i: Fossil Imprint. - Prague : National Museum, Czech Republic. - 2533-4050 .- 2533-4069. ; 74, s. 135-158
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 16. |
- Friis, Else Marie, et al.
(författare)
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Fossil seeds with affinities to Austrobaileyales andNymphaeales from the Early Cretaceous (early-middle Albian) of Virginia andMaryland, U.S.A: new evidence for extensive extinction near the base of theangiosperm tree
- 2018
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Ingår i: Transformative Paleobotany: Papers to Commemorate theLife and Legacy of Thomas N. Taylor. - London : Academic Press. - 9780128130124 ; , s. 417-435
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Bokkapitel (refereegranskat)abstract
- 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.
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| 17. |
- Friis, Else Marie, et al.
(författare)
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Geminispermum, an Early Cretaceous (early–middle Albian) cupulate unit from the angiosperm-dominated Puddledock flora of eastern North America
- 2019
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Ingår i: Acta Palaeobotanica. - Warsaw : W. Szafer Institute of Botany Polish Academy of Sciences. - 0001-6594 .- 1427-6402 .- 2082-0259. ; 59, s. 229-239
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Tidskriftsartikel (refereegranskat)abstract
- A new genus and species, Geminispermum virginiense, is described based on a well-preserved coalified cupulate reproductive unit recovered from the Early Cretaceous (early–middle Albian) Puddledock locality, Virginia, U.S.A. The reproductive unit is bisymmetrical and consists of an axis that bifurcates into two cupule-bearing stalks, each in the axil of a bract. Each cupule stalk bears a single non-valvate cupule recurved towards the center of the reproductive unit. The cupule opens distally by a short transverse slit with a distinct upper margin. Each cupule almost completely encloses a single orthotropous seed that is free from the cupule except at the base. The nucellus is also free from the integument except at the basal point of attachment. Geminispermum combines features of the ovulate structures of Caytoniales, Umkomasiales (= Corystospermales, including Doyleales) and Petriellales, but cannot be included in any of these existing orders as they are currently understood. The recurved, closed, non-valvate cupules are particularly similar to those of Caytonia, Petriellaea and Reymanownaea in external morphology, but differ in being one-seeded. The cupules of Geminispermum differ from the one-seeded cupules of Umkomasiales in being non-valvate and in having only a single cupule per bract. Geminispermum is perhaps most similar to the one- or two-seeded non-valvate cupules of Ktalenia from the Early Cretaceous of Argentina, but Ktalenia is poorly preserved, details of cupule architecture are uncertain, and the cupules appear to be associated with a single strongly dissected bract. Geminispermum is currently the only unequivocal seed plant cupule recovered from the Early Cretaceous Potomac Group and is distinct from all previously described cupulate reproductive structures.
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| 18. |
- Friis, Else Marie, et al.
(författare)
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Hedyosmum-like fossils in the Early Cretaceous diversification of angiosperms
- 2019
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Ingår i: International journal of plant sciences. - Chicago : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 180, s. 232-239
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Tidskriftsartikel (refereegranskat)abstract
- Premise of research. Early Cretaceous Hedyosmum-like fossils are important because they provide information on the pistillate flowers and fruits of plants that produced Asteropollis pollen, which is common and widely distributed very early in the history of angiosperms. Hedyosmum (Chloranthaceae) is also the only extant genus for which there is a plausible fossil presence at such an early stage of angiosperm evolution.Methodology. The fossils were sieved out of unconsolidated sediments and cleaned with HF, HCl, and water. External morphology and internal anatomy were studied using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy.Pivotal results. New information on Hedyosmum-like fossils is provided based on pistillate flowers and fruits with adhering Asteropollis pollen from the Early Cretaceous of Portugal. The fossils are assigned to a new Early Cretaceous taxon, Hedyflora crystallifera, which in external morphology is closely similar to extant Hedyosmum. However, the fossils differ from the extant genus in having a crystalliferous endotesta with cells that have endoreticulate infillings, a feature characteristic of all extant Chloranthaceae except Hedyosmum. Extant Hedyosmum has a thin, unspecialized seed coat. This new discovery confirms earlier predictions that an endotestal seed coat is ancestral for Chloranthaceae as a whole but has been lost in the lineage leading to extant Hedyosmum.Conclusions. Hedyflora confirms the divergence of the Hedyosmum lineage from other Chloranthaceae very early in the angiosperm radiation but refutes these early fossils as evidence of extant Hedyosmum in the Early Cretaceous.
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| 19. |
- Friis, Else Marie, et al.
(författare)
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Kenilanthus, a new eudicot flower with tricolpate pollen from the Early Cretaceous (early-middle Albian) of eastern North America
- 2017
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Ingår i: Grana. - London : Taylor & Francis. - 0017-3134 .- 1651-2049. ; 56:3, s. 161-173
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Tidskriftsartikel (refereegranskat)abstract
- Fossil evidence strongly indicates that the initial phylogenetic diversification of angiosperms during the Early Cretaceous involved many kinds of plants that are now extinct, and suggests that their closest living relatives are among extant angiosperms in the ANA-grade (Amborellales, Nymphaeales, Austrobaileyales), Chloranthaceae, eumagnoliids and early lineages of monocots (Friis et al. 2011). Eudicots also appear early in the diversification of angiosperms, as evidenced by the presence of isolated tricolpate pollen grains in palynological assemblages from around the Barremian-Aptian boundary onwards (Penny 1988, 1991; Doyle 1992; Hughes 1994). Early tricolpate pollen is known from floral remains and in coprolites in early mesofossil floras from Portugal (Friis et al. 2010a, 2011) and there are scattered reports of eudicot leaf fossils from Aptian to mid-Albian strata (e.g. Jud 2015). Eudicots become more common towards the end of the Albian. The earliest pollen grains that can unequivocally be assigned to eudicots are tricolpate, like the pollen produced by many extant early-diverging lineages in this clade. Tricolporate pollen grains, which occur in some basal grade eudicots, but that are more characteristic of core eudicots (Furness et al. 2007), are also present in the fossil record by the end of the Early Cretaceous.
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| 20. |
- Friis, Else Marie, et al.
(författare)
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Melloniflora, a new extinct multiparted flower from the Early Cretaceous of Virginia
- 2020
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Ingår i: International journal of plant sciences. - : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 181, s. 887-897
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Tidskriftsartikel (refereegranskat)abstract
- remise 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.
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| 21. |
- Friis, Else Marie, et al.
(författare)
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Microsporangiophores from the Early Cretaceous (Berriasian) of Bornholm, Denmark, with comments on a pre-angiosperm xerophytic flora
- 2021
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Ingår i: Review of Palaeobotany and Palynology. - Amsterdam : Elsevier. - 0034-6667 .- 1879-0615. ; 293
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Tidskriftsartikel (refereegranskat)abstract
- A new taxon, Skyttegaardia galtieri, is described based on microsporangiophores with Monosulcites/Cycadopites pollen isolated from clays collected at the Skyttegård 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.
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| 22. |
- Friis, Else Marie, et al.
(författare)
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Multiparted, apocarpous flowers from the Early Cretaceous of eastern North America and Portugal
- 2020
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Ingår i: Fossil Imprint. - Prague : Czech National Museum. - 2533-4069 .- 2533-4050. ; 76, s. 279-296
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 23. |
- Friis, Else Marie, et al.
(författare)
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Rightcania and Kvacekispermum: Early Cretaceous seeds from eastern North America and Portugal provide further evidence of the early chloranthoid diversification
- 2018
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Ingår i: Fossil imprint. - Prague : National Museum, Czech Republic. - 2533-4050 .- 2533-4069. ; 74, s. 65-76
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 24. |
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| 25. |
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| 26. |
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| 27. |
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| 28. |
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| 29. |
- Friis, Else Marie, et al.
(författare)
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Tanispermum, a new genus of distinctive hemi-orthotropous to hemi-anatropous angiosperm seeds from the Early Cretaceous of eastern North America
- 2018
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Ingår i: American Journal of Botany. - USA : Wiley. - 0002-9122 .- 1537-2197. ; 105, s. 1369-1388
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 30. |
- Friis, Else Marie, et al.
(författare)
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The Early Cretaceous mesofossil flora of Catefica, Portugal: angiosperms
- 2022
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Ingår i: Fossil Imprint. - Prague : National Museum. - 2533-4050 .- 2533-4069. ; 78:2, s. 341-424
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Tidskriftsartikel (refereegranskat)abstract
- 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. Thereare 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 morethan half of all specimens. Angiosperms also dominate in number of species, but because the non-angiosperm fossils have notbeen studied in detail the total number of species in the flora is not yet established. Sixty-seven species of angiosperms arerecognized. 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 numberof 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.
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| 31. |
- Friis, Else Marie, et al.
(författare)
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THE EARLY CRETACEOUS MESOFOSSIL FLORA OF TORRES VEDRAS (NE OFFORTE DA FORCA), PORTUGAL: A PALAEOFLORISTIC ANALYSIS OF AN EARLYANGIOSPERM COMMUNITY
- 2019
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Ingår i: Fossil Imprint. - Prague : National Museum. - 2533-4069. ; 75, s. 153-257
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Tidskriftsartikel (refereegranskat)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.
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| 32. |
- Friis, Else Marie, et al.
(författare)
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The endothelium in seeds of early angiosperms
- 2019
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Ingår i: New Phytologist. - 0028-646X .- 1469-8137. ; 224, s. 1419-1424
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Tidskriftsartikel (refereegranskat)abstract
- 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 fossil history of angiosperms (for references, see Friis et al., 2011). The fossils recovered from such mesofloras include well‐preserved flowers, fruits and seeds that can be compared in detail with those of living plants to provide an integrated picture of early angiosperm evolution. Data from mesofossil floras have also provided many of the fossil calibrations used to model the age of different angiosperm clades based on molecular data (Magallón & Sanderson, 2005; Beaulieu et al., 2015; Magallón et al., 2015). From the Early Cretaceous these kinds of fossils have so far only been discovered in deposits from Portugal and eastern North America, where they are sometimes abundant, and often have an exquisite preservation of cellular details.
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| 33. |
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| 34. |
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| 35. |
- Herendeen, Patrick, et al.
(författare)
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Palaeobotanical redux: revisiting the age of the angiosperms
- 2017
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Ingår i: Nature Plants. - London : Springer Science and Business Media LLC. - 2055-0278. ; 3, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 36. |
- Herrera, Fabiany, et al.
(författare)
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Reconstructing Krassilovia mongolica supports recognition of a new and unusual group of Mesozoic conifers
- 2020
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Ingår i: PLOS ONE. - : PLoS. - 1932-6203. ; 15:1, s. 1-21
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Tidskriftsartikel (refereegranskat)abstract
- Previously unrecognized anatomical features of the cone scales of the enigmatic Early Cretaceous conifer Krassilovia mongolica include the presence of transversely oriented paracytic stomata, which is unusual for all other extinct and extant conifers. Identical stomata arepresent on co-occurring broad, linear, multiveined leaves assigned to Podozamites harrisii, providing evidence that K. mongolica and P. harrisii are the seed cones and leaves of the same extinct plant. Phylogenetic analyses of the relationships of the reconstructed Krassilovia plant place it in an informal clade that we name the Krassilovia Clade, which also includes Swedenborgia cryptomerioides–Podozamites schenkii, and Cycadocarpidium erdmanni–Podozamites schenkii. All three of these plants have linear leaves that are relatively broad compared to most living conifers, and that are also multiveined with transversely oriented paracytic stomata. We propose that these may be general features of the Krassilovia Clade. Paracytic stomata, and other features of this new group, recall features of extant and fossil Gnetales, raising questions about the phylogenetic homogeneity of the conifer clade similar to those raised by phylogenetic analyses of molecular data.
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