LAUSR

During the Cenomanian–Turonian transition interval, larger benthic foraminifera became extinct or suffered decreases in terms of their diversity. Anoxic/dysoxic conditions of oceanic bottom water masses and potentially seawater acidification during this pivotal time also affected ecological niches in the shallow epeiric domain and resulted in the demise of many taxa of benthic foraminifera worldwide. Nevertheless, exceptions to this pattern have been reported too. Here, evidence is presented for mass occurrences of larger benthic foraminifera (Perouvianella peruviana) from the Western Platform in Peru that were not affected by environmental conditions related to the Cenomanian–Turonian transition. A new architectural analysis of P. peruviana tests found in abundance in central Peru has permitted a detailed update on its systematic and functional morphology. The paleoenvironment associated with the P. peruviana mass occurrence was characterized by mesotrophic conditions, perhaps in one way or another similar to the environmental parameters that lead to Aptian and Albian larger benthic foraminifera mass occurrences at the southern Tethyan margin (‘Orbitolina levels’). Algae and small, cosmopolitan r-strategist foraminifera coexisted with P. peruviana. Moreover, a first description of the soritid taxa Pseudopeneroplis oyonensis n. gen., n. sp. is provided. Interestingly, the superposition of local and global environmental patterns onto the Western Peruvian shelf water masses triggered a mass development of the Perouvianella population coincident with Oceanic Anoxic Event 2. Conversely, the migration of foreign complex-shelled K-strategist larger benthic foraminifera from neighboring realms was inhibited.