Planktonic foraminifera are a ubiquitous and abundant group of marine pelagic Rhizaria. Their fossil shells are extensively used to date sedimentary rocks and to reconstruct past climate changes. As a result, their taxonomic descriptions are based on features of adult shells as found in the sediments and are not ideal for the identification of specimens collected from the plankton. To aid researchers working with extant planktonic foraminifera, we present a taxonomic guide specifically tailored towards the identification of living specimens. In this first leaflet we describe eleven species of the microperforate Candeinidae and genera Berggrenia, Bolivina, Dentigloborotalia and Neogallitellia, including most of the species commonly considered as “small and obscure”. The descriptions are supported by hand-drawn illustrations of the shells and wherever possible by light microscopic images of cytoplasm-bearing specimens representing adult and pre-adult life stages. Diagnostic characters are listed in an overview table to aid rapid identification.