Two new species of rhopalopsyllid fleas: Ectinorus lareschiae, n. sp. and Ectinorus morenoi, n. sp. are described from Laguna Blanca National Park, Neuquén Province, Argentina. Ectinorus lareschiae was collected from the sigmodontid rodents Phyllotis xanthopygus (Waterhouse) and Reithrodon auritus (Fischer), while E. morenoi was also collected from P. xanthopygus in addition to the sigmodontid rodent Abrothrix longipilis (Waterhouse) and the didelphid marsupial Thylamys pallidior (Thomas). The female sex of E. lareschiae is unknown. During these studies, it was noted that Beaucournu and Gonzalez (2005) did not include Ectinorus alejoi Hastriter, 2002 (in Hastriter et al. 2002) in their diagnosis of Ectinorus lagidium. A diagnostic character is therefore provided to distinguish males of E. alejoi from males of E. lagidium. A listing of all known species of Ectinorus is included to facilitate future work.