Drymaeus ribeiroi (Ihering, 1915) (Gastropoda: Bulimulidae) is a synonym of Drymaeus nigrogularis (Dohrn, 1882): reassessment of a poorly known species set in motion by in situ records

Numerous recent records on the citizen-science platform iNaturalist, initially identified by us as Drymaeus ribeiroi, prompted a re-evaluation of its taxonomic status and geographic range. A mid-western species from Brazil, D. ribeiroi was originally described as a subspecies of the poorly known Amazonian D. nigrogularis and later elevated to species rank without stated justification. We reassessed its status through examination of type material, additional museum specimens, and new photographic evidence. Our analysis shows that both nominal taxa are sympatric, share key diagnostic features, particularly the dark-brown pigmentation on the parietal peristome, supporting the treatment of ribeiroi as a junior synonym of nigrogularis. The iNaturalist records also expand the known distribution of the species across the southern and eastern margins of the Amazon rainforest. The observations of living individuals reveal a distinctly yellow head-foot with potential phylogenetic relevance. The occurrence of the species in both forested and urbanised habitats, and its prevalence within the Amazon “deforestation arc”, shows that improved sampling and assessment of its conservation status should be urgently undertaken.