ABSTRACT: Newly discovered sediment samples, manuscripts, and articles from the early eighteenth century, concerning the species we know today as Ammonia beccarii (Linnaeus), provide a good example of what is possibly the first micropaleontological analysis in the history of Earth Sciences. Thiswas performed by Jacopo Bartolomeo Beccari on fossil foraminifera in 1711, including detailed information in terms of: i) analysed material, ii) separation technique of the microfossils, iii) description of the assemblage and specifically of the dominant species (giving attention to coiling, sutures, internal structures, size, weight, and preservation state), iv) paleoenvironmental interpretation (supported by comparison with modern assemblages). The rigorous analytical approach and thorough interpretation, not only the accurate description of the observed fossil species, allow to assign to Beccari the distinction of "the founder of micropaleontology". The lectotype of Ammonia beccarii (Linnaeus 1758) is described from Beccari's original samples in order to clarify the taxonomic status of this species (Vaiani et al. 2019).