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Reithrodon auritus is a living sigmodontine with one of the broader temporal records, from the lower Pliocene of Argentina. Its populations in northwestern Argentina are today found patchily and restricted to five high-elevation and isolated localities in open areas of highland grasslands vegetation (at >3000 m). During the Pleistocene and early Holocene, R. auritus would have had a broader range, reaching lower altitudes everywhere and being one of the dominant small mammal species in some fossil localities. In this note, we summarize the known Pleistocene and early Holocene fossil record of R. auritus in northwestern Argentina, provide new paleontological sites for the species, and make comments concerning the paleoenvironmental implications of its presence at such lower altitudes. The paleontological evidence indicates that during the Pleistocene and early Holocene, R. auritus inhabited around 1000 m below their current altitudinal distribution in the eastern Andean ranges, with populations clearly more abundant than today. The fossils of R. auritus are indicative of colder and perhaps more xeric paleoenvironmental conditions, characterized by open areas with sparse grassy vegetation as those developed today around 3000 m elevation. [ABSTRACT FROM AUTHOR]

A gastropod and ostracod fauna from Agua Verde river locality, Catamarca, is described and included in the Andalhuala Formation, dated as 5.22 ± 0.9 Ma (Lower Pliocene). The following taxa of gastropods were identified: Biomphalaria straminea (Dunker), Physa cf. acuta Draparnaud, Chilina fluminea (Maton), Lymnaea aff. viatrix d’Orbigny, Succinea aff. meridionalis d’Orbigny, Heleobia sp. y Potamolithus aff. lapidum (d’Orbigny), associated in the same assemblage with the ostracods Cyprideis sp. cf. C. salebrosa hartmanni Ramirez, 1967, Cyprideis sp., Cypridopsis sp. cf. C. vidua (O. F. Müller) and Cyamocytheridea? sp. The association reflects a shallow, small fresh water body, with some water level variations, developed in a warm-humid climate of the Neotropical Region. [ABSTRACT FROM AUTHOR]

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