Freshwater Dalyelliidae from the Nearctic (Platyhelminthes, Rhabdocoela): new taxa and records from Ontario, Canada and Michigan and Alabama, USA

Abstract

Nine taxa of Dalyelliidae Graff, 1908 collected from limnic habitats in Ontario, Canada and Michigan and Alabama, USA are discussed. Two taxa are new to science. Pseudodalyellia alabamensis n. gen. n. sp. has a unique combination of characters (Microdalyellia-type stylet with two proximal heteromorphic axes of different size and two distal axes with long spines flanking a central spiny plate, uterus without uterine sphincter, glandular protrusion in male atrium) and is therefore placed in a new genus. Gieysztoria choctaw n. sp. is strikingly similar to the Amazonian G. chiqchi Damborenea et al., 2005 but differs by having 13 symmetrically arranged, heteromorphic spines of different size on its fenestrated girdle. Gieysztoria pavimentata (Beklemischew, 1926) Ruebush & Hayes, 1939 and Gieysztoria rubra (Fuhrmann, 1894) Ruebush & Hayes, 1939 discovered in Alabama are the first records for these species in the Nearctic. Remarks on the morphology and distribution of the new North American records of Gieysztoria dodgei (Graff, 1911) Ruebush & Hayes, 1939, Microdalyellia fairchildi (Graff, 1911) Gieysztor, 1938, Microdalyellia rossi (Graff, 1911) Gieysztor, 1938, Castrella truncata (Abildgaard, 1789) Hofsten, 1907 and Castrella pinguis (Silliman, 1884) Fuhrmann, 1900 are given. For G. pavimentata, M. fairchildi and C. truncata, new localities from the Palearctic are also mentioned.