A new species of Platyla (Mollusca: Gastropoda: Aciculidae) fills a biogeographic gap in the Mediterranean.

The family Aciculidae Woodward, 1854 is endemic to the southwestern Palaearctic and includes tiny operculate land snails living in the soil or underground, and seldom encountered. The genus Platyla Moquin-Tandon, 1856 is restricted to Europe west of the Great and Pannonian Steppes, occurring on islands only in the Ionian Sea off Greece, along the Dalmatian coast of Croatia, and in the Tyrrhenian Sea on Sicily, Sardinia and Elba (Boeters et al. 1989; Cianfanelli et al. 2000; Bodon & Cianfanelli 2008; Subai 2009). Its absence from the Balearic archipelago remained as a puzzling gap, given its palaeogeographic relationship with surrounding land masses. Herein I describe a very rare new species of Platyla from the island of Mallorca, which is most similar to congeners living in Sicily, around the Adriatic and in the Pyrenees, supporting the hypothesis of Neogene vicariance through microplate dispersal in the western Mediterranean. Intensive search of non-marine Mollusca throughout the Balearics during the last four decades yielded only a single site inhabited by Aciculidae. The first specimen (an empty shell) was found in the rugged head of a temporary stream in the Special Area of Conservation "la Victòria". After thoroughly searching the area, four more shells were collected among debris at the stream's mouth. Several species in this family are likewise known from very few, or even single specimens, attesting to their rarity, troglophilic habitats and sparse distribution. Shells were carefully cleaned with distilled water and amylase, with the aid of a fine brush and dissecting tweezers. They were examined and photographed with a Nikon D100 camera mounted on an Olympus SZ40 scope. Composite full-focused images were obtained with Helicon software and mounted with GIMP, and enlarged photographs were used as template for drawing from natural with precise dimensions. Specimens are deposited at the Museu de Ciències Naturals de Barcelona (MZB) and the author's scientific collection (CRA). The classification of plant communities follows Llorens et al. (2007).