Large benthic agglutinated foraminifers possess subepidermal wall textures similar to the keriothecal textures observed in some Fusulinana. Considering the gap exceeding 50 million years in the record of the first alveolar large agglutinated Mesozoic forms (Textulariana) and their last known Palaeozoic microgranular homologues (Fusulinana), the two groups have been regarded as distinct lineages. The discovery of Wernlina reidae gen. et sp. nov. in Late Triassic carbonate rocks of a Panthalassan terrane questions this assumption. This new form, the earliest unequivocal Mesozoic ‘agglutinated' alveolar foraminifer, originated from an Endotebidae (Fusulinana). The identification of a Triassic missing link between microgranular and agglutinated foraminifers not only fills the 50 million year gap but also challenges current foraminiferal classification.