Austrolimnius cleidecostae, a new species of riffle beetle (Coleoptera: Elmidae) from Brazil with habitat notes and updated key of the Brazilian species of the genus

Austrolimnius cleidecostae sp. nov. is one of the smallest species of Elmidae from the Neotropical region. The new species is described and illustrated based on male and female specimens. This species represents the first record in Elmidae of mandibles with an articulated, sclerotized process on inner subapical edge. The specimens were collected from streams in the Atlantic rainforest of Sao Paulo and Santa Catarina, and habitat notes are given. An updated key for the Austrolimnius Carter & Zeck, 1929 of Brazil is provided. Austrolimnis browni Hinton, 1971 and A. musgravei Hinton, 1939 are recorded for the first time from Brazil.