Georissa is a genus of minute land snails, terrestrialgastropodmollusks in the family Hydrocenidae. Although the species are best known for living on the surface of limestone rocks, they are often also found in and on the vegetation and on non-calcareous rocks. One species, Georissa filiasaulae, is cavernicolous. It is only known from two caves in the Sepulut area of Sabah, Malaysian Borneo, where its above-ground sister species, Georissa saulae, inhabits the rocks outside of the cave, and is connected to the cave snail via narrow zones of hybridization at the cave entrances. Possibly, G. filiasaulae has evolved without ever having been fully separated from its ancestor, a process known as speciation-with-gene-flow.[2][3]
^Schilthuizen M., Rutten E. J. M. & Haase M. (2012). "Small-scale genetic structuring in a tropical cave snail and admixture with its above-ground sister species". Biological Journal of the Linnean Society105: 727-740. doi:10.1111/j.1095-8312.2011.01835.x
^ abHaase M. & Schilthuizen M. (2007). "A new Georissa (Gastropoda: Neritopsina: Hydrocenidae) from a limestone cave in Malaysian Borneo". Journal of Molluscan Studies73(3): 215-221. doi:10.1093/mollus/eym020.
