Data from: Paleoenvironmental and paleobiological origins of coccolithophorid genus Watznaueria emergence during the Late Aalenian-Early Bajocian

The latest Aalenian–early Bajocian time interval (ca. 171-169 Ma) is marked by a global reorganization of oceanic plates with the Central Atlantic opening and the formation of the Pacific plate. This time interval is also marked by a global geochemical perturbation of δ13C with a negative excursion at the Aalenian/Bajocian boundary and a positive excursion during the early Bajocian. Evolutionary diversifications of marine invertebrate taxa, namely ammonites, radiolarians, and coccolithophorids, are recorded at that time. Concerning coccolithophorids, this interval witnesses the diversification and expansion of the most successful Mesozoic genus: Watznaueria. In this study, we explore the potential environmental, ecological, and biological forcing at the origin of Watznaueria diversification and its effect on the coccolith assemblages through quantification of the absolute and relative abundances of calcareous nannofossils in two Middle Jurassic key sections: Cabo Mondego (Portugal) and Chaudon-Norante (France). In both sections, we find an increase in nannofossil absolute abundance and flux at the beginning of the lower Bajocian, coeval with an increase in absolute and relative abundances of Watznaueria spp., followed by a plateau in the middle and upper part of the lower Bajocian. The increase of Watznaueria spp. is synchronous with a decrease in relative abundance of other major coccolith taxa, whereas the absolute abundance of these species did not decrease. During the climatically driven early Bajocian eutrophication event, Watznaueria spp. integrated into the calcareous nannoplankton community in two successive evolutionary steps involving first W. contracta and W. colaccicchii, and second W. britannica and W. aff. manivitiae. Step 1 was driven by an increase in niche carrying capacities linked to the early Bajocian eutrophication. Step 2 was driven by specific adaptation of the newly evolved Watznaueria species to bloom in nutrient-rich environments not exploited before. These evolutionary events have initiated the 100-Myr reign of Watznaueria over the calcareous nannoplankton community.

最新的阿伦阶-巴柔阶早期（Aalenian–early Bajocian）时间间隔（约171-169 Ma）以全球大洋板块重组为标志，伴随中大西洋开裂与太平洋板块形成。该时段同时记录了全球地球化学扰动：碳同位素δ¹³C在阿伦阶/巴柔阶界线处出现负偏移，巴柔阶早期则出现正偏移。彼时海洋无脊椎动物类群——包括菊石、放射虫与钙板金藻（coccolithophorids）——均发生演化辐射。针对钙板金藻而言，该时段见证了中生代最成功的属——瓦茨瑙藻属（Watznaueria）的多样性演化与地理扩张。本研究通过对两个中侏罗世关键剖面：葡萄牙卡波蒙德戈（Cabo Mondego）与法国肖东-诺朗特（Chaudon-Norante）中的钙质超微化石绝对丰度与相对丰度进行定量分析，探究了驱动瓦茨瑙藻属演化辐射的潜在环境、生态与生物学因素，及其对钙板金藻组合的影响。在两个剖面中，研究均发现下巴柔阶底部的钙质超微化石绝对丰度与沉积通量均出现上升，这与瓦茨瑙藻属（Watznaueria spp.）的绝对丰度及相对丰度提升同步；随后在下巴柔阶中上部，该类群丰度进入平台期。瓦茨瑙藻属丰度的提升与其他主要钙板金藻类群的相对丰度下降同步，但这些类群的绝对丰度并未出现降低。在气候驱动的巴柔阶早期富营养化事件中，瓦茨瑙藻属通过两个连续的演化步骤融入钙质超微浮游群落：第一步为W. contracta与W. colaccicchii，第二步为W. britannica与W. aff. manivitiae。第一步由与巴柔阶早期富营养化相关的生态位容纳量提升所驱动；第二步则由新演化出的瓦茨瑙藻物种对此前未被利用的富营养环境形成藻华的特异性适应所推动。这些演化事件开启了瓦茨瑙藻属在钙质超微浮游群落中长达1亿年的统治地位。