The “Falcatae”, a new Gondwanan species group of Gieysztoria (Platyhelminthes: Dalyelliidae), with the description of five new species

Abstract Gieysztoria Ruebush and Hayes, 1939 , the most species-rich genus of limnic rhabdocoels (Platyhelminthes: Dalyelliidae), is subdivided into several groups based on stylet morphology. Most taxa are known from the Palearctic and the Neotropics. Very little is known about limnic, free-living flatworms in other tropical and subtropical regions. In this contribution five new species of Gieysztoria are described from India, Australia and South Africa, all former Gondwanan fragments. Gieysztoria garudae  n. sp., G. ashokae  n. sp. and G. ramayana  n. sp. were collected in Goa (India), G. stokesi  n. sp. in the Northern Territory (Australia) and G. zuluensis  n. sp. in KwaZulu-Natal (South Africa). All these new species share a typical, very complex stylet morphology, which deviates strongly from that of the groups into which the bulk of the other species within this genus are classified. Therefore a new subgroup, the “Falcatae”, is erected. In addition, four known species could also be included in this subgroup. Possible homologies, common ancestry and biogeographic distribution patterns are discussed.