Numerous specimens of Echiniscus rufoviridis (Heterotardigrada, Echiniscidae) were recorded and studied from urban localities in Argentina. Since the first description of this species by <A HREF="#DuBois-Raymond">Du Bois-Raymond Marcus in 1944</A> on Brazilian specimens, it had not been recorded again. The validity of the species is confirmed, its geographic distribution is extended to Argentine localities and new data are provided on its morphology (optical and SEM) and its bioecology. Echiniscus rufoviridis can be clearly separated from the E. viridis, the closest species within the "viridis group", by the possession of depressions with pores on the surface of the cuticle, instead of papillae. On the other hand, an ecological similarity with E. testudo is proposed. This latter species occupies, albeit with low tolerance, urban environments in Europe