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The hypothetical Aalenian biotic crisis: reconsidering the literary evidence and agenda for future research

ABSTRACT Despite of significant progress in palaeobiology, the discovery of new evidence for biotic crises cannot be excluded. Various notions about the Aalenian (Middle Jurassic) biotic crisis are scattered in the palaeontological and geological literature. This information needs to be summarised and re-evaluated before making any further judgements. A critical analysis of the existing literature suggests the absence of solid grounds for a definitive understanding of this event. Nonetheless, it is clear that several fossil groups like foraminifers and marine reptiles were stressed (at least, regionally), and eustatic fluctuations and changing palaeoclimate can be related to perturbations in the fossil record. This view is supported by a preliminary check of the long-term fossil records and the regional evidence. The general hypothesis of the Aalenian biotic crisis is worthy of a research agenda, and future global and regional studies of many fossil groups in different palaeoenvironmental contexts will either prove or disprove this hypothesis.