The highest stages of the stratigraphic range of the planktonic foraminiferal Rotalipora cushmani were investigated in a 313-k.y.-long interval of the classical Tethyan Bottaccione section (Gubbio, Italy), the type locality of the C_org- rich Bonarelli Level, which is the sedimentary expression of the worldwide latest Cenomanian oceanic anoxic event 2 (OAE 2).The disappearance of R. cushmani is associated with the major turnover of marine microfauna and microflora that involves both planktonic and benthic foraminifera, and calcareous nannofossils, slightly before the onset of OAE 2, which, according to current available data, was triggered by a massive pulse of submarine mafic volcanism accompanying the initial emplacement of the Caribbean large igneous province (CLIP). This pulse of volcanic activity probably turned the climate in a strengthened greenhouse mode, accelerating continental weathering and increasing nutrient supply in oceanic surface waters via river runoff and triggering higher fertility in the global ocean. Our investigation shows that the marine biotic turnover started ~55 k.y. before the onset of OAE 2 and is closely coeval with the first major episode, as recorded by the unradiogenic trend in ¹⁸⁷Os/¹⁸⁸Os, of the ongoing magmatic activity of the CLIP, which produced increasing pCO₂, ocean dissolution and/or acidification with a severe carbonate crisis and fertilization through enormous quantities of biolimiting metals. The marine microfauna and microflora reacted rapidly to new conditions of higher pCO₂ and fertility by undergoing marked changes following three main steps. We evaluate this pattern and postulate that the first pulse of volcanogenic CO₂ from the CLIP emplacement (ca. 94.2 or 94.6 Ma) played a fundamental role in the marine biotic turnover recorded shortly before the onset of OAE 2 and notably in the local or regional disappearance of R. cushmani in the central-western Tethys.