| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Friis, Else Marie, et al.
(författare)
-
Catanthus, an Extinct Magnoliid Flower from the Early Cretaceous of Portugal
- 2021
-
Ingår i: International journal of plant sciences. - : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 182, s. 28-45
-
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.
|
|
| 5. |
- Friis, Else Marie, et al.
(författare)
-
Chlamydospermous seeds document the diversity andabundance of extinct gnetalean relatives in Early Cretaceous vegetation
- 2019
-
Ingår i: International journal of plant sciences. - Chicago : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 180, s. 643-666
-
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.
|
|
| 6. |
- Friis, Else Marie, et al.
(författare)
-
Early and Mid-Cretaceous Aristolochiaceous Seeds from Portugal and Eastern North America
- 2022
-
Ingår i: International journal of plant sciences. - Chicago : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 183:7, s. 587-603
-
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.
|
|
| 7. |
|
|
| 8. |
- Friis, Else Marie, et al.
(författare)
-
Early flowers of primuloid Ericales from the Late Cretaceous of Portugal and their ecological and phytogeographic implications
- 2021
-
Ingår i: Fossil Imprint. - Prague : Národní muzeum. - 2533-4050 .- 2533-4069. ; 77:2, s. 214-230
-
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.
|
|
| 9. |
- Friis, Else Marie, et al.
(författare)
-
Exceptional preservation of tiny embryos documents seed dormancy in early angiosperms
- 2015
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 528, s. 551-554
-
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.
|
|
| 10. |
- Friis, Else Marie, et al.
(författare)
-
Extinct diversity among Early Cretaceous angiosperms: mesofossilevidence of early Magnoliales from Portugal
- 2019
-
Ingår i: International Journal of Plant Sciences. - Chicago : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 180, s. 93-127
-
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.
|
|
