Review of Palaeobotany and Palynology最新文献

The Lower Devonian Rhynie chert preserves a remarkable diversity of microorganisms from an early terrestrial ecosystem. However, eukaryotic microalgae are rarely reported. This study describes Harpericystis verecunda gen. et sp. nov., a probable green alga (Chlorophyta) from the Rhynie chert, using more than 50 specimens, all of which are enclosed in a degraded land plant axis. Specimens include single cells up to 8(− 10) μm in diameter, dyads, decussate and tetrahedral tetrads, and small colonies comprised of 8 or 16 cells. Other specimens consist of both larger cells and tetrads of smaller cells, which either are the result of successive cell divisions (autosporogenesis), or have formed from multinucleate parent cells by directed cytokinesis. Cells, cell groups, and colonies are surrounded by a colorless mucilage. In some cases, it appears that the constituent cells of the colonies are interconnected by thickened plates of their envelopes or short processes. Harpericystis verecunda was non-motile and most likely planktonic. It shows similarities with various present-day colony-forming green algae, in particular with Coelastrum (Sphaeropleales) and Sphaerocystis (Chlamydomonadales), but its systematic affinity remains unresolved. This discovery is further evidence that intra-plant environments facilitated the preservation of fragile microbial life in the Rhynie setting.

The role of climate variability in the expansion and collapse of the Harappan Civilization in South Asia has been a subject of intense research and debate among archaeologists, Quaternary climate scientists, meteorologists, climatologists, historians, geographers, archaeobotanists, and anthropologists. Moreover, high-resolution palaeoclimatic studies have challenged the previous perspectives attributing societal collapses solely to socio-political and economic factors. These studies have revealed that periods of abundant rainfall, resulting from climate amelioration and/or due to seasonality: Winter vs. Summer precipitation, often coincided with the peak of socio-economic, cultural, and technological advancements in various civilizations. Conversely, abrupt climatic changes or rapid climatic changes, such as prolonged droughts, led to the destruction of irrigation systems, agricultural devastation, and widespread famines. These climatic disruptions triggered cultural adaptations, migrations, and sometimes even the collapse of entire civilizations. Climate forcing, particularly solar variability, played a primary role in repeated societal displacements, migrations, and deurbanization across different regions in the past. Additionally, the intensified El Niño-Southern Oscillation, a shift of the Indian Ocean Dipole to a strong negative state, and the southward migration of the Inter-Tropical Convergence Zone contributed to an extended period of weakened Summer Monsoons of South Asia and increased aridity. This depletion of water resources triggered the general demographic shift vis-à-vis the 4.2 ka event. The displacement was a response to a weakened Summer Monsoons of South Asia. In this research review article, we aim to understand the role of climate variability and explore the complex socio-climatological linkages in the mysterious displacement of once-thriving, highly advanced, widespread, and urbanized Harappan Civilization at the 4.2 ka.

This study focuses on newly collected plant fossils from the Cisuralian successions of the Khenifra Basin in Central Morocco, revealing a diverse assemblage dominated by conifers, pteridosperms, and sphenophytes. The assemblage includes eleven taxa of vegetative and reproductive organs preserved as compressions and impressions. Two pteridosperm species taxa (Neurodontopteris auriculata, Odontopteris subcrenulata) are recorded for the first time from Central Morocco, whereas other taxa are known from the early Permian deposits of Bou Achouch and Tiddas basins. Contrary to previous interpretations, the flora is does not exhibit a mixed character, but instead exhibits a distinct Euramerican affinity, despite the absence of the widespread callipterids Autunia conferta and A. naumannii. These similarities between this flora and coeval Euramerican floras highlight the significant biogeographical connections across Pangea during the Cisuralian. The plant fossil assemblage is dominated by meso- to xerophilous species adapted to drought, with rare hygrophilous elements adapted to humid habitats, reflecting a heterogeneous landscape with various vegetation types.

A palynostratigraphic study of the upper Cunga and lower Quifangondo deposits in the Cabo de São Brás section, Kwanza Basin, Angola, has revealed a new pollen named Syncolpraedapollis angolensis nov. gen. sp. nov. This finding was part of a wider survey in the upper Cunga and lower Quifangondo deposits of the Cabo de São Brás section, Kwanza Basin, Angola, covering the latest Eocene to the latest Oligocene.

The novel pollen features unique characteristics, notably a 3-syncolporate structure with well-defined and distinctive pores. The pollen grain is adorned with a free but irregular reticulum with an irregular polygonal mesh. Syncolpraedapollis angolensis nov. gen. sp. nov. is sporadically but consistently observed within the latest Eocene-latest Oligocene interval, conspicuously absent in the underlying Eocene sediments (lower Cunga Formation) and occurring infrequently in the latest Oligocene sediments (lower Quifangondo Formation). Thus, it is plausible to infer a limited age range, likely restricted to the latest Eocene-latest Oligocene, as previous studies in the Kwanza Basin have not documented this pollen.

The asexual morph of Meliolaceae has long been a focus of attention for mycologists because there has been a lack of research to establish the asexual morph cycle of Meliolaceae. Besides asexual morph, only a few research works have also been done on the setae (mainly ascomatal setae) of Meliolaceae. In this connection, the use of reliable fossil evidence in evolutionary studies is obligatory. The present study fills this lacuna by reporting the in-situ occurrence of a new enigmatic fossil-genus and species Palaeomeliola indica Kundu and Khan, gen. et sp. nov. with mycelial setae, ascomata, ascomatal setae, ascomatal conoid cells, 4-septate ascospores, phialides, and phialoconidia on the cuticle fragments of a compressed disease-symptomatic monocot leaf recovered from the middle Siwalik (Late Miocene; ca. 12–8 Mya) of Himachal Pradesh, western Himalaya. Palaeomeliola indica is the first fossil-species of Meliolaceae having all sexual and asexual morphs. From this point of view, our new fossil fungus is very distinctive and establishes the greatest preserved fossil record of Meliolaceae. The preserved sexual and asexual morph data sheds new insight into the systematics, life cycle, and evolutionary lineages of Meliolaceae. Furthermore, the findings of this study will form the basis for any future life cycle reconstruction and morphological character evolutionary study of Meliolaceae.

Fossil pollen data are valuable for understanding past spatio-temporal variations in plant diversity. However, deducing robust patterns of fossil pollen-assemblage properties is challenging due to factors related to pollen production, dispersal, and fossilisation; sediment sampling; and nomenclature and taxonomy of the fossil pollen grains reflecting the vegetation that produced them. If the composition pattern of the most recent fossil pollen assemblage concords with those in modern or surface pollen assemblages from the same location(s), the pattern can be regarded as robust.

Using recent (50–500 years) fossil pollen and surface pollen assemblages of angiosperms compiled from the same geographic area of Central Asia, we analyse spatial patterns in compositional turnover and phylogenetic dispersion. These are widely used to quantify different aspects of plant diversity.

Despite differences in the data regarding spatial coverage, number of pollen records, and number of pollen taxa, the spatial pattern in the modern and fossil pollen-assemblage properties across climate zones is broadly similar. Especially, the latitudinal patterns of pollen-assemblage properties are strikingly similar between both data types. However, the degree of concordance varies according to the diversity metric being analysed, and the magnitudes of the metric may differ between both data types. When the data are compiled, processed, and standardised following consistent criteria and analysed using appropriate metrics and methods, spatial patterns in pollen-assemblage properties of fossil pollen data are as robust as those in surface pollen data (∼ modern vegetation). Therefore, regional patterns of compositional turnover and phylogenetic dispersion can be confidently inferred from older fossil assemblages through the Holocene.

Many permineralized conifer stems and trunks have been documented from the Jurassic strata of the Xinjiang Uygur Autonomous Region (Xinjiang), Northwest China. Xylem anatomical studies have showed that these stems and trunks belonged to a diverse range of plants. However, the leaf phenology and the paleoclimatic and paleoenvironmental significance of these fossil plants have rarely been studied. We quantitatively analyzed the anatomical characteristics of a permineralized conifer stem—Yiwupitys elegans Gou et Feng 2023—from the Middle Jurassic Xishanyao Formation in northeastern Xinjiang, which has distinct and wide growth rings in the secondary xylem. Analyses of the Mean Sensitivity and Ring Markedness Index of the growth rings suggest that a stable paleoclimate with regular seasonal fructifications likely prevailed during the Middle Jurassic in this area. The statistical analyses of cell diameters and anatomical features of leaf traces in six successive growth rings indicate that this fossil plant was deciduous. Our study elucidates the ecophysiological characteristics of a Middle Jurassic conifer plant and provides new insights into the corresponding paleoclimate and paleoenvironment based on quantitative cellular analysis of the fossil stem.

A new assemblage of fossil wood of Paleocene age from Seymour Island, Antarctic Peninsula, is described. Conifer species have been identified, belonging to the fossil genera Agathoxylon, Phyllocladoxylon, Protophyllocladoxylon, and Podocarpoxylon. Angiosperm fossil wood species are assigned to Nothofagoxylon, Caldcluvioxylon, and Myrceugenellites. New wood types have been described with possible affinity to Atherospermataceae and Asteraceae (daisy family). A newly identified fossil angiosperm species, Aextoxicoxylon jacksius, has been recorded from Antarctica for the first time. It shares traits with modern Aextoxicon punctatum and other Aextoxicoxylon wood from South America but is considered a separate species due to significant differences in vessel density, ray height, and frequency. This study indicates, in accordance with previous studies that conifers were the most common elements in the Paleocene Antarctic vegetation. In particular, Agathoxylon being the most dominant wood type. Nothofagoxylon was the most common angiosperm wood type. Overall the composition of the Antarctic Paleocene vegetation deduced from the presence of fossil wood resembles that of the modern warm to cool temperate forests of Tasmania, New Zealand and southern South America. Possible upland and lowland forest types have been identified, with the lowland forests likely most similar to the modern mixed cool temperate forests on South Island, New Zealand, and Tasmania. The upland forests were similar to the modern open canopy Araucaria-Nothofagus forests on the high Andes today.

In 2019 the Rijksmuseum in Amsterdam acquired a set of oak stocks about which little was known. Radiocarbon wiggle-matching revealed that the tree used to make the stocks was likely felled around 1800 C.E., while ancient DNA indicated the tree's growing zone to be Central Europe. The question remained where and how these stocks were used. To answer these questions, traces of former use at the surface of the stocks were studied and sediment from cracks and holes in the stocks was analyzed for pollen, fungal spores, diatoms and other algae, phytoliths, and insects. The biogeographical information of the recorded taxa shows that the stocks had been used in the western Iberian Peninsula. Although the sediments could have entered in various ways and at various moments, a dungeon seems the most likely context in which these stocks have been used.