A new species of Microdalyellia (Rhabditophora : Rhabdocoela : Dalyelliidae) from temporal freshwater rock pools in Utah, USA

Abstract

A new species of Microdalyellia Gieysztor, 1938 is described from a temporal freshwater pool in Utah, USA. This new species is characterized by the detailed structure of the stylet, which is of the Microdalyellia-type and consists of a crossbeam that carries two proximal shafts, two distal branches each carrying 5-7 hollow spines, and a median process in between both these spiniferous branches. The most remarkable feature is the presence of a second connection (or crossbeam) between both shafts, giving the proximal part of the stylet the appearance of a plate with a large window. The species' affinities within the taxon Dalyelliidae Graff, 1905 are discussed. Following the discussion, Gieysztoria rastafariae Therriault and Kolasa, 1999 is transferred to the taxon Microdalyellia, because of the presence of a Microdalyellia-type stylet, which closely resembles that of the newly described species.