Abstract

The species of Hyalella living in the southern extreme of South America have several common morphological features. The uniqueness of this morphology presents a good argument for inferring phylogenetic relationships among them. The species are concentrated, although not exclusively, in the Patagonia of Chile and Argentina. The group is called here 'patagonica complex'. These species are not the only Hyalella present in the area, however. Hyalella simplex Schellenberg, 1943, with no morphological affinities to the patagonica complex is also present, and is one of the few other species outside the complex living in the continental extreme south of South America. Hyalella simplex is redescribed in this paper. Two species of the patagonica complex have been recorded for the area: H. neonoma Stock and Platvoet, 1991 and H. araucana Grosso and Peralta, 1999. H. fossamancinii Cavalieri, 1959, another species in the complex, is found high in the Andes. The new species H. franciscae described in this work is added to the complex.