Conference Agenda

We present a new assemblage of diverse and exceptionally well-preserved megaspores from Egypt, based on material from core samples from the Upper Cretaceous (Coniacian–Santonian) Matulla Formation in the Gulf of Suez. Hundreds of megaspore specimens of at least three genera significantly extend our knowledge of the flora of the Matulla Formation, which is based solely on dispersed palynomorphs. Well-preserved sporocarps with in situ micro- and megaspores of a Marsileaceae-like water fern are of particular importance. The retrieved spores closely resemble Ariadnaesporites. Together with dispersed Ariadnaesporites megaspores and associated microspores, these fossils provide further evidence for an evolutionary link and possibly ancestral position of Ariadnaesporites within Salviniales. The diverse array of megaspores and other associated mesofossils identified in this study suggests that they are under-represented in the macrofloras of Egypt and were likely essential constituents of the vegetation. The mixed character of the assemblages and the presence of damaged specimens and fragments in all of them support the interpretation of lacustrine to paralic environments of deposition for the studied sedimentary units.

The Jiaolai Basin of China is the southernmost edge of the distribution of the northern Jehol Biota and an important area which bears both the northern and southern palaeogeographical fauna representative species. The Laiyang flora in the Jiaolai Basin is located in the transitional region between the Early Cretaceous southern and northern flora of China. Currently, research on the plants in the transitional region between the northern and southern flora are relatively weak. Our study of specimens has enriched our understanding of the floral landscape in the transitional region between the north and south flora. Cretaceous wood fossils are well preserved in China and 66 species of 29 genera have been reported up to now, which are widely distributed in China. However, in the Cretaceous Shandong Province, there are few records of wood fossils. So far, only one genus and two species have been reported.
A new material of fossil wood is described from the Early Cretaceous Zhifengzhuang Formation of Laiyang Group in Jingzhi area of Anqiu City, Jiaolai Basin, Shandong Province. The present specimen has uniseriate to triseriate pits on the radial walls of tracheids, taxodioid cross-field pitting and other characters. This discovery contributes to a better understanding of fossil wood diversity in Jiaolai Basin during the Cretaceous. Through the well preserved growth rings of the specimens, it can be inferred that the environmental paleoclimate of the Early Cretaceous in Shandong Province was generally arid, with some areas being humid.

The evolution of Cretaceous vegetation is closely associated with the evolution of angiosperms. In the Early Cretaceous, alluvial forests were formed and dominated by gymnosperms, particularly conifers. Angiosperms partly formed the forests' understorey, but grew more as shrubs, predominantly on slopes and disturbed habitats. In the Late Cretaceous, angiosperms became dominant in most of the terrestrial palaeoenvironments in Europe. They grew particularly on alluvial plains, where lauroid and platinoid angiosperms prevailed in the Cenomanian; in the Coniacian-Santonian, this environment was enriched by eudicots, particularly from the Normapolles complex.

In terms of plant strategies, angiosperms from the Early Cretaceous exchanged a ruderal (disturbed) strategy for a competitive strategy in the Late Cretaceous. Conifers grew in alluvial plains in the Portuguese Early Cretaceous, while they dominated salt marshes and wetlands in the European Late Cretaceous. During the Cretaceous, they exchanged a competitive strategy in the Early Cretaceous for a stress-tolerant strategy in the Late Cretaceous.

Among angiosperms, monocots show sharp differences in occurrence in European Cretaceous. While in the Early Cretaceous monocots are rare or entirely absent, their massive occurrence in the Late Cretaceous, particularly in the Gosau Cretaceous is of interest. It fits with the theory, that monocots originally evolved in Gondwana. Hypotheses have been developed that the Alpine orgonic system brought Gosau Cretaceous flora as passengers from the African coast, riding on the Adriatic Microplate.

Multiple Dramatic Episodes of Environmental Changes (EECs) occurred during the gradual intensification of the Early Cretaceous greenhouse climate. During this period, the hydrological cycle intensified, leading to enhanced global weathering, increased productivity, and ultimately massive organic carbon burial. However, these conclusions are primarily based on paleoenvironmental studies of marine sedimentary records, whereas research on long-term terrestrial paleoenvironmental fluctuations remains extremely limited. In recent years, we have conducted extensive palynological studies on long-sequence Lower Cretaceous continental deposits in the inland regions of northwestern China. Our findings reveal that the Late Jurassic flora, dominated by Classopollis (~80%), rapidly transitioned into a humid-adapted flora in the earliest Early Cretaceous (Berriasian–Valanginian), characterized by bisaccate Pinaceae pollen, trilete fern spores, and Taxodiaceae pollen. By the mid-Early Cretaceous (Hauterivian–early Barremian), the vegetation shifted again, this time to a conifer-dominated flora with bisaccate pollen exceeding 80%. In the late Early Cretaceous (Aptian–Albian), the vegetation reverted to a Classopollis-dominated assemblage (~80%), representing a Cheirolepidiaceae-dominated flora, alongside the appearance of early angiosperm groups. These repeated transformations in Early Cretaceous vegetation clearly reflect revolutionary shifts in climatic conditions, evolving from the hot and arid Late Jurassic to a warm and humid climate in the earliest Early Cretaceous, then transitioning to a cooler, more humid climate in the mid-Early Cretaceous, before finally returning to a prolonged stable hot and arid regime. This long-term climatic sequence may represent a response to the progressive intensification of the Early Cretaceous greenhouse climate.

Keywords: Early Cretaceous, palynology, climatic changes, flora, inland

The Cretaceous period was marked by a pronounced greenhouse climate, characterized by the diversification and development of key biological groups and substantial transformations in terrestrial ecosystems. Based on a comprehensive study of plant diversity and the evolution of terrestrial climatic environments during the Early Cretaceous in Jiuquan area of NW China, a diverse assemblage of well-preserved gymnosperm and early angiosperm fossils has been identified. The gymnosperm fossils encompass a diverse range of taxa, including Ephedra, Pseudofrenelopsis, Brachyphyllum, Pagiophyllum, Torreya, Athrotaxites, Araucaria, Carpolithus, Pterophyllum, Nilssoniopteris, Phasmatocycas and Podozamites. The angiosperm fossils identified include Gansufructus, Fairlingtonia, and Jixia. Integrated with comprehensive research on the paleo-climate and environment of the study area, the findings indicate that the intensification of the greenhouse climate, the aridification of the paleo-environment, fluctuations in paleoatmospheric CO₂ concentrations, and frequent wildfire events collectively played a significant role in shaping the transformation of vegetation landscapes, particularly the diversification of early angiosperms in the Jiuquan area during the Early Cretaceous. These achievements not only offer crucial evidence for the radiation evolution of plants in the northwest inland region of China during the Early Cretaceous period, but also possess substantial scientific significance for evaluating the potential impacts of greenhouse climate on biodiversity and ecosystems.

Key words: Early Cretaxeous, Jiuquan area, fossil plants, biodiversity, terrestrial ecosystems

This work is supported by the National Natural Science Foundation of China (42372006 and 42272029) and the Fundamental Research Funds for the Central Universities (lzujbky-2022-ey18).

As a crucial disturbance factor in terrestrial ecosystems, wildfires have played a significant role in forest ecosystems since the Silurian Period. During the Cretaceous, a critical transitional phase in Earth's history, wildfire activities exerted profound impacts on evolution of ecosystems. In this study we investigate the palaeowildfire events recorded in the Second Member of the Nenjiang Formation (Campanian) in the Dayangshu Basin, eastern Inner Mongolia, northeastern China. Microstructural analysis of charcoal fossils using scanning electron microscopy (SEM) revealed well-preserved anatomical features of various plant organs, including xylem, leaves, and seeds. Inertinite reflectance ranging from 1.73% to 6.48%, with a mean value of 3.35%, suggesting that the fire temperatures could reach up to approximately 580℃. These data indicate the occurrences of crown fires during this period. Palynological sequences suggest that before the fire broke out, fern spores were more abundant, while gymnosperms and angiosperms were less abundant. A marked increase of angiosperm pollen (mainly represented by Nymphaeacidites) was observed immediately after palaeowildfire. This appears suggest that the fire enhanced surface erosion and consequent nutrient influx into aquatic systems that promoted aquatic plant proliferation. Conifer pollen started to predominate the palynoflora soon after the wildfire event. Such successional floral/palynofloral pattern suggests that wildfires could probably eliminate some ferns, while conifers ultimately dominated in this fire-prone environment due to its fire resistance.