The description of Rheotanytarsus dactylophoreus sp. nov. is based on adult males, pharate males and pupal exuviae collected in low and middle mountain streams located in the Eastern Pyrenees and Corsica is presented. The most distinctive character in the adult male is the unusually long, finger-like, digitus and in the pupal exuviae is the thoracic horn which is spinulate laterally (extending from swollen base into tapered apical half). The distribution of R. dactylophoreus sp. nov. indicates that this pyreneocorsican species is a Tyrrhenian faunal element which spread westwards to mountain streams of the Eastern Pyrenees perhaps during the repeated waves of migration from the Paleocene (Montian) till the late Miocene. doi: 10.5324/fn.v31i0.1375. Published online: 17 October 2012.