Deciphering the very early phase of angiosperm evolution using palynology

被子植物（开花植物）首次出现的时间在古植物学中是一个相当有争议的问题。化石记录清楚地表明早白垩世冠群被子植物的显著多样化，前10亿1500万年仅以化石花粉为代表。然而，这种前阿普梯时期的被子植物花粉记录是非常零碎的（基于现场样品），并且通常基于缺乏精确地层分配的地层。考虑到早白垩世从裸子植物为主的生态系统到被子植物为主的生态系统的变化代表了较年轻的白垩纪陆地生物史上最戏剧性的转折之一，这种缺乏年代久远的化石证据是令人震惊的。为了填补这一空白，我们建议研究位于葡萄牙的卢西塔尼亚盆地，一个地区众所周知的特殊被子植物中化石和丰富的花粉植物群的地层剖面。所选剖面涵盖了海相近岸相的Valanginian - Barremian地层。精确的地层控制可以通过现有的生物和层序地层信息与新的锶和碳同位素化学地层学相结合来实现。花粉组合将研究与不同的成像技术，包括透射光以及扫描电子显微镜（包括。单颗粒分析）。这种方法将能够与现有的记录，特别是从威尔德盆地和邻近的葡萄牙中化石的地方进行比较。有关更广泛的植物群落背景的信息将通过研究伴随的孢粉植物群来获得。该建议的化学地层学和孢粉学相结合的方法，旨在提供新的见解非常早期的演化和被子植物的多样化，并在早白垩世的陆地环境动力学。

The timing of the first appearance of angiosperms (flowering plants) is a matter of considerable debate in palaeobotany. The fossil record clearly indicates significant diversification of crown-group angiosperms in the Early Cretaceous, with the first 10 ‒ 15 Myr being represented by fossil pollen only. However, this pre-Aptian record of angiosperm pollen is very fragmentary (based on spot samples) and often based on findings from strata lacking precise stratigraphic assignment. Given the fact that the Early Cretaceous change from gymnosperm- to angiosperm-dominated ecosystems represents one of the most dramatic turnovers in the terrestrial biotic history of the younger Phanerozoic, this scarcity of well-dated fossil evidence is startling. To fill this gap, we propose to study stratigraphic sections located in the Lusitanian Basin of Portugal, an area well known for its exceptional angiosperm mesofossils and rich pollen floras. The chosen sections cover Valanginian – Barremian strata in marine near-shore facies. Precise stratigraphic control can be achieved by the combination of existing bio- and sequence-stratigraphic information with new strontium- and carbon-isotope chemostratigraphy. Pollen assemblages will be studied with different imaging techniques including transmitted light as well as scanning electron microscopy (incl. single grain analysis). This approach will enable comparison with existing records, in particular from the Weald basin and from adjacent Portuguese mesofossil localities. Information on the broader plant community context will be obtained by studying the accompanying palynoflora. The combined chemostratigraphic and palynological approach of this proposal aims at providing new insights into the very early evolution and diversification of angiosperms and into terrestrial environmental dynamics during the Early Cretaceous.