Idiopyrgus Pilsbry, 1911 (Gastropoda, Tomichiidae): a relict genus radiating into subterranean environments

The freshwater gastropod fauna in Brazil presently consists of circa 180 known species, though this is deemed an underestimate. The little-studied cavern faunas have been considered a potential source of undescribed species, particularly regarding the Truncatelloidea. Here, based on new collection efforts in caves in Bahia state, Brazil, we describe two new troglobitic species of Idiopyrgus (Tomichiidae): Idiopyrgus eowynae sp. nov. and Idiopyrgus meriadoci sp. nov. We improve upon the previous molecular phylogeny of this genus and take the opportunity to reclassify Spiripockia umbraticola Simone & Salvador, 2021, as Idiopyrgus umbraticola (Simone & Salvador, 2021), comb. nov. The genus Idiopyrgus now contains ten species, reinforcing the presence of Tomichiidae in Brazil as a relict lineage that largely radiated into cave environments. Furthermore, considering that so far only snapshots of their biology are known, we have collated all the information currently available from the literature and field observations on the cavernicolous species of Idiopyrgus. Notably, due to human action in the area where the two new species have been found, they can already be considered vulnerable.