A joint expedition between the Museum of Comparative Zoology of Harvard University (Cambridge, Massachusetts, USA) and the Museo Argentino de Ciencias Naturales (Buenos Aires, Argentina) explored outcrops in west-central Argentina during autumn of 1958. The team led by Alfred S. Romer collected fossils from several Cenozoic outcrops from Mendoza, San Juan, and La Rioja provinces. Some of the recovered fossils were previously published, including gastropods, birds, turtles, and mammals. However, other specimens, which belong to the Vertebrate Paleontology collection at the Museum of Comparative Zoology, remained unknown and even uncatalogued until the present contribution. Here, we present this peculiar collection for the first time, providing an updated taxonomic list of the vertebrate remains. Based on the studied material, we identified 1) Glyptodontidae (cf. Propalaehoplophorus), Dasypodidae (Stenotatus sp.), Mesotheriidae (cf. Altitypotherium), Macraucheniidae (Cramaucheniinae gen. et sp. indet.) and Rodentia indet. in the Aisol Fm.; 2) Megatheriidae (Pyramiodontotherium sp.) and Macraucheniidae (Macraucheniinae gen. et sp. indet.) in the Tunuyán Fm.; 3) Dasypodidae indet. in the Mariño Fm.; 4) Hegetotheriidae (Hemihegetotherium sp., Pachyrukhinae gen sp. indet., Paedotherium sp.) and Rodentia indet. in the Pilona Fm.; and 5) Cingulata indet., Mesotheriidae (Pseudotypotherium sp.), Hegetotheriidae (Tremacyllus sp.), Chinchiliidae indet., and Hydrochoeridae indet. in the Huachipampa Fm. The reports of the Romer collection from Argentina allow the establishment of biochronological correlations between the lesser-known faunas from west-central Argentina and faunas from other areas of South America.