| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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