Review of Palaeobotany and Palynology最新文献

We describe two small, compressed seeds from the Gulf of Mexico Coastal Plain that display a reticulate-foveolate seed coat pattern as species of Passiflora subgenus Passiflora. One was obtained from the basal layer of the Catahoula Formation in Wayne County, Mississippi, and is late Oligocene in age (25–23.8 Ma), supported by planktonic foraminferal and nannofossil zones. The other is from a Pleistocene river terrace (luminescent dating of 85–82 ka) on the banks of the Mobile River in Alabama. The Oligocene seed is tridentate (consisting of a central apical appendage and well-displayed lateral protrusions to the sides of this appendage), symmetrical, and has a palisade seed coat structure with ruminate endosperm. Its characters allow tentative placement within supersection Laurifolia and series Tiliifolia. Extensive comparisons with seeds of extant species of Passiflora subgenus Passiflora serve as the basis for recognizing it as a new species, Passiflora axsmithii sp. nov. The Pleistocene seed is obovate, slightly asymmetrical, has a small crown around the base of the apical appendage, and insubstantial lateral projections. As the Pleistocene seed is geologically young and fits the description of seeds produced by the native extant species Passiflora incarnata (supersection Passiflora, series Passiflora), we consider it very likely to be a representative of that species. The Oligocene seed is the earliest reliable record, thus far, of genus Passiflora. The Pleistocene seed is likely the earliest record, to date, of the extant species P. incarnata.

Exceptionally well-preserved impression fossils of Cyrillopteris (ex. Odontopteris) orbicularis (Halle) comb. et emend. nov. have been described from the lower part of the middle–upper Permian Upper Shihezi (Upper Shihhotse) Formation in Yangquan City, Shanxi Province, North China. For the first time, this typical Cathaysian seed fern is confirmed to have a bipartite frond with two bipinnate branches, comparable with that of C. genuina (Grand'Eury) Laveine et Oudoire from the Pennsylvanian of France. Entire-margined cyclopteriod elements occur in the proximal portion of the long petiole. With increasing proximity of the bifurcation, the cyclopteroid elements progressively differentiate into pinnae with individual pinnules. True intercalary pinnules, which would be fully inserted on the primary rachides, are not present. Characteristics of our new specimens provide new information on the frond architecture of C. orbicularis (Halle) comb. et emend. nov., and allow a relatively complete circumscription of the overall features of this taxon, an emendation of the species diagnosis, and the presentation of an accurate frond reconstruction. Specimens of C. orbicularis comb. et emend. nov. are preserved with mesophytes and xerophytes from the same interval, demonstrating the vegetation in the research area grew under a seasonal subhumid to semiarid climates during the late Guadalupian.

Pollen analysis of a late medieval layer (15th–16th century AD) recovered in the archaeological site of Kastrì (Epirus, Greece) highlighted the occurrence of large amounts of stephanocolpate Lamiaceae pollen grains. Morphometric analysis, by means of Light and Scanning Electron Microscopy, allowed three different pollen types to be identified within the family. In particular, the structure of the bireticulate exine, which is only visible under SEM observation, revealed to be a diagnostic feature for genus and even species identification. This was possible thanks to comparison with modern Lamiaceae species that were selected on the basis of pollen morphological similarity and geographical distribution. The results of comparison, achieved through K-nearest neighbour classification, led to ascribe the subfossil pollen types to the genera Salvia, Mentha and Thymus and to propose S. nemorosa/glutinosa/pratensis, M. arvensis and T. praecox as the most probable species to be associated with the subfossil grains. The significance of such a large quantity of Lamiaceae pollen is not easy to decipher. However, the co-occurrence in the sample of grazing indicators would suggest that these aromatic herbs were probably related to feeding or caring for flocks, in line with the archaeological interpretation of the investigated medieval structure as a shelter for shepherds as well as with the current use of these plants as forage supplements.

The recent geological history of the Northern Andes is characterized by the interaction of dynamic surface processes such as volcanic activity, fluvial erosion, mass movements, etc. that have shaped landscapes for millennia. Despite its great geological and biological importance, the long-term ecological history of middle-elevation tropical habitats (between 1000 and 2500 m.a.s.l.) is unknown, due to the scarcity of suitable paleo archives preserving the paleoecological signal, leading to a critical data gap. This manuscript reports well-preserved subfossil woods of the Pleistocene volcanoclastic deposits from the Central Cordillera of Colombia. Four wood specimens are described and identified as Terminalioxylon gumminae sp.nov., Andesanthus risaraldense sp.nov., Anacardium quindiuense sp.nov., and Chrysochlamys colombiana. This report demonstrates the potential of volcanic deposits in the Northern Andes as paleo archives, and contributes to the fossil record of the tropical Andes, as it contains elements of mid-altitude vegetation preserved in association with the Pleistocene volcanic activity of the Central Cordillera. The environments where these subfossil species lived resemble present environmental conditions. This is a baseline for future paleobotanical exploration and paleoenvironmental analyses.

This paper presents the results of the explorations carried out in the western sector of the Iberian Central System (western Gredos, Béjar, Gata and Estrela mountain ranges). The macroremains found allow detailing the model of the landscape transformation, the composition and extension of their vegetal formations throughout the Holocene.

Ninety-nine woody macroremains, 3 bark remains and 8 pinecones were located from eight sites between 875 and 1860 m above sea level, among which 15 radiocarbon dates were made. The taxonomic identification of two trunks found in Estrela allows us to document the local presence of Pinus cf. sylvestris ca. 6600 cal BP in this site. The same taxon also appears at the western end of Gredos between ca. 1700–2800 cal BP at approximately 1300 m. These remains expand the Holocene distribution of P. cf. sylvestris in the Central System known to date, both temporally and geographically.

In parallel, the macroremains analysed document the composition of high mountain scrub (Cytisus type, Erica cf. arborea) in Béjar (ca. 1860 m), as well as mixed scrub-woodland formations in Gata (975–1180 m), which included deciduous Quercus, Betulaceae and Ericaceae. The presence of P. pinaster at ca. 6200 cal BP and 1180 m in this mountain range constitutes the earliest palaeobotanical evidence of this species recorded in Gata.

The main results support the continuous persistence of plant formations in which P. sylvestris, P. nigra, and P. pinaster would have formed part throughout the Iberian Central System during the Holocene in a wide altitudinal range (1100–1840 m).

We used a combined approach (lithofacies and palynology) and multivariate analyses to reconstruct the different depositional environments and changes in the plant communities throughout the middle to late Kungurian in the tropical Pangea. The late Paleozoic terrestrial biotas underwent changes under the pressure of a general aridification trend and a warming event that changed biota composition favoring drought-tolerant taxa during the Artinskian. Few studies integrate the different terrestrial ecosystem components to reconstruct palaeoenvironments and climate changes throughout the Cisuralian (early Permian). We analyzed several sedimentary successions of different stratigraphic positions intercalated in well-dated volcanic units of the megacaldera of the Athesian Volcanic Group (Southern Alps, northern Italy). The obtained palynofacies and quantitative sporomorph records with an exceptional high resolution (∼ 10 Ma) evidence a palaeoenvironmental/climatic change in the plant communities from the middle to the late Kungurian. The late Kungurian shows a higher diversity in the plant communities with a dominance of seed ferns and a higher relative abundance of xeromorphic-hygromorphic sporomorph taxa. This suggests the presences of more stable and putatively more humid environmental conditions in respect to the middle Kungurian. Furthermore, a direct comparison between lithofacies and all primary components of the palynofacies assemblages permits to characterize lacustrine and alluvial depositional environments since these studies are underrepresented for terrestrial environments.

The Lower Devonian Rhynie cherts yield abundant fossils of many different microorganisms. One of them is an oblong cell (up to 15 μm long) on a slender stipe; a basal attachment disc or cushion is visible in some specimens. This fossil was originally described (but not named) based on specimens associated with fungal spores in an aquatic environment, and its striking resemblance to present-day epibiotic freshwater algae of the genera Characiopsis (Eustigmatophyceae) and Characium (Chlorophyceae) was noted. However, none of the original specimens had been preserved attached to a substrate. Here, I revisit the fossil using new, better-preserved specimens from the same setting, most of which are attached to land plant cuticles. Although the affinities of the fossil remain unresolved, the new material reinforces its status as a discrete aquatic life form, most likely belonging to the algae. A new fossil-genus, Characrhynium gen. nov., and species, C. amoenum sp. nov., are therefore formally proposed for it. Characrhynium amoenum is evidence that submerged surfaces in the Rhynie ecosystem could be overgrown with epibiotic autotrophs.

Extinct Mesozoic seed plants are key for understanding the evolution and relationships of seed plants, including homologies among their reproductive organs. Recent discoveries of exceptionally well-preserved fossils have greatly enhanced knowledge of the ovulate reproductive organs of Mesozoic seed plants, but research on the corresponding pollen organs is more limited. Here we describe a new species of Mesozoic pollen organ, Harrisiothecium sanduense sp. nov. based on material from the Upper Triassic Yangmeilong Formation in Hunan, South Central China. Harrisiothecium sanduense consists of a thick central axis bearing lateral secondary branches arranged mainly in a single plane and almost distichous. The lateral branches are unbranched or bifurcate, and bear one or two terminal capsules each consisting of two valves on either side of a median hinge. Each valve bears a row of six to seven elongated pollen sacs on the inner face. Harrisiothecium sanduense is similar to Harrisiothecium marsilioides from the Upper Triassic of Greenland and Hydropterangium roesleri, which we transfer to Harrisiothecium roesleri comb. nov., from the Upper Triassic of Germany, and like both species is also associated with pinnate leaves of the seed fern Ptilozamites. Harrisiothecium sanduense differs from Harrisiothecium marsilioides and Harrisiothecium roesleri in its more flattened structure with lateral branches that bear no more than one or two capsules. Harrisiothecium shares similarities to Pramelreuthia dubia, Pteroma, Pteruchus, Antevsia and Townrovia, as well as the structures that bear the pollen sacs in Bennettitales.

Although in the second half of the Eocene, thick sub-bituminous coal seams were deposited in the Hungarian Paleogene Basin, it is not known under what climatic conditions these strata were formed. To investigate this, the paleoenvironmental conditions were reconstructed for the upper Lutetian-middle Priabonian period. The reconstruction of paleoclimatic conditions was based on the Coexistence Approach, for which the climatic data of the extant relatives of 15 fossil plant genera provided the basis of the analysis. Most (87%) of the extant relatives of the studied fossil plant genera can be found most frequently in tropical climate regions. Plotting the reconstructed average mean annual temperature (23.4 ± 3.9 °C) and precipitation (2375 mm ± 964 mm) values to the Whittaker Plot and Peltier's plots it was found that the region had a tropical monsoon climate during the upper Lutetian- middle Priabonian period. At the same time, there was a great difference between the precipitation sums of the wettest and driest months (409 ± 178 mm and 59 ± 56 mm), indicating a tropical monsoon-like climate with strong chemical weathering conditions. Currently, in climatically similar regions, tropical rainforest and tropical moist deciduous forest vegetation grow under tropical rainforest and tropical monsoon climates, and lateritic soils are formed. Furthermore, relatively rich mangrove plant associations flourish along the coasts of these regions, indicating that a part of the peat may have been deposited in mangroves. The contemporary lateritic soils, which later became the protoliths of bauxites, provided a poor nutrient supply for coastal vegetation, likely due to peat accumulation.

The Middle Miocene Zhangpu biota (∼ 14.7 Ma)—from the Fotan Formation in the Zhangpu area, southeastern China—indicates that the rainforest had reached at least 24.2°N at that time. In this study, pollen analysis was carried out in six outcrop sections of this formation in the Zhangpu area. Based on the succession of palynoflora, three developmental stages of vegetation were recognized. From the late Early Miocene to the Middle Miocene Climatic Optimum (MMCO) (the first stage), the vegetation underwent frequent disturbances associated with the volcanic activities, in which two sub-stages are recognizable. During the earlier sub-stage (late Early Miocene), the vegetation was similar to the modern subtropical evergreen broad-leaved forest and exhibited a warming trend; then during the later sub-stage (MMCO), the tropical forest developed with the appearance of diverse tropical and subtropical taxa. The second stage, which was also within the MMCO, should be an intermission of volcanic eruptions, during which the tropical forest, especially the tropical montane rain forest, steadily developed without disruptions. And during the third stage (Middle to Late Miocene), the altitudinal vegetation belts of tropical montane rain forest significantly lowered which was accompanied by the occurrence of drought-tolerant taxa, implying the significant climatic cooling and moisture reduction. The above evolutionary phases of the vegetation in the Zhangpu area show a close relationship with the Miocene global climatic variations, which might be the main driving force of the vegetation changes in the southeast coast area of China during that period.