The land snails of Malpelo island, Colombia

The fauna of the volcanic island Malpelo located west of Colombia's Pacific coast includes only two species of land snails. One is a new endemic species of the subulinid genus Ischnocion, with which Rectobelus, Microbeliscus and Nannobeliscus are provisionally synonymized. Ischnocion conica new species differs from other species of the genus in the conical shell with radial palatal folds in juvenile stages. The other land snail species from Malpelo Island represents a new endemic thysanophorid genus. This genus, Malpelina (type species: Malpelina labiata new species), differs from other taxa of the Thysanophoridae in the yellowish-brown, depressed-globular shell with a distinctly thickened peristome, a broad glandular genital atrium, the lack of a vagina, a long penis, a long and exposed talon and the lack of entocones from all radular teeth. Malpelina is more closely related to Central American taxa than to thysanophorids from the Colombian mainland. Thus, it is more likely that Malpelo Island has been colonized by Malpelina from the north in accordance with palaeotectonic reconstructions. It is less clear whether Ischnocion reached Malpelo Island from Central or from South America, because the genus is distributed in both regions. Both species are patchily distributed on Malpelo and live under rocks in high densities. Their abundances increase towards higher altitudes. There is some segregation concerning the resting sites. Ischnocion conica rests on the soil or partially buried, while M. labiata almost always hangs from the underside of rocks