Historically there has been taxonomic confusion among some Lygophis and Erythrolamprus species (previously belonging to the genus Liophis) due to their high similarity in color and general body form, in addition to a lack of understanding of their natural history and distribution. Lygophis anomalus is a common snake thought to be widely distributed in the Pampas and Chaco regions of Argentina, Uruguay, southern Brazil and Paraguay. While studying a sample of Lygophis anomalus specimens from throughout its distributional range, we observed that those from several northern provinces in Argentina were misidentified. The aim of this study is to clarify the area of occurrence of Lygophis anomalus, by combining a revision of the available literature and traditional morphology (body measures and lepidosis). Using only confirmed records of L. anomalus, we performed ecological niche modelling (ENM) as a means of corroborating our results. After analyzing body measures and lepidosis, the specimens from Córdoba (mostly above 600 masl) and San Luis provinces were identified as Lygophis vanzolinii. Individuals from Chaco, Formosa and Misiones were identified as Eryhtrolamprus almadensis and finally, snakes collected in Jujuy, Salta and Tucumán were identified as E. ceii. ENM recovered low values of suitability occurrence (< 0.5) for the species in Paraguay and the Argentine provinces of Chaco, Formosa, Jujuy, Misiones, Salta, San Luis and Tucumán, suggesting that specimens from these localities were incorrectly identified as L. anomalus. Despite the fact that the only known reference specimen for L. anomalus in Paraguay (but without specific locality data) is confirmed to belong to this species, ENM as well as exhaustive field work suggest that L. anomalus does not occur in the aforementioned country. Our results indicate that Lygophis anomalus distribution is restricted to Uruguay, southern Brazil and the Argentinian provinces of Buenos Aires, Corrientes, Córdoba, Entre Ríos, and Santa Fe.