New light on the late Middle Miocene–Early Pliocene representatives of Lagostomus (Chinchillidae, Rodentia) from Cerro Azul Formation, Argentina

• Published in: Journal of South American earth sciences 2023-08, Vol.128, p.104481, Article 104481
• Main Authors: Montalvo, Claudia I., Sostillo, Renata, Rasia, Luciano L.
• Format: Article
• Language: English
• Subjects: Center of Argentina; Juvenile individuals; Lagostominae; Neogene
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2023.104481

Lagostominae (Rodentia, Caviomorpha, Chinchillidae) include a single living species, the plains vizcacha Lagostomus maximus, but representatives of this subfamily are registered since the Early Miocene. The oldest record of this genus was recently extended to the late Middle Miocene in one locality of center of La Pampa Province. Previously, from levels of the Late Miocene Cerro Azul Formation in Buenos Aires and La Pampa provinces, two species of Lagostomus were recognized based on specimens from two localities, L. telenkechanum from Arroyo Chasicó (Buenos Aires Province) and L. pretrichodactyla from Salinas Grandes de Hidalgo (La Pampa Province). In the present work, new materials from these two and other localities of the Cerro Azul Formation are analyzed. This study supports the presence of both species, which had coexisted in several of the analyzed assemblages. The studied sample includes several incomplete specimens and others interpreted as juvenile individuals, which can only be determined as Lagostomus sp. Also, a similar behavior to that of the extant L. maximus (i.e., gregarious populations with fossorial habits) is proposed to explain the different representation of Lagostomus in each assemblage. In Cerro Azul Formation the presence of representatives of Lagostomus is mainly linked with levels with paleosols and accumulations by predator activity. Finally, we conclude that this genus has less biostratigraphic value than previously thought, at least for central Argentina. •New chinchillids materials were recovered from Cerro Azul Formation.•The oldest record of Lagostomus is late Middle Miocene.•Two species of Lagostomus are confirmed for assemblages from Cerro Azul Formation.•Specimens interpreted as juvenile individuals can only be determined as Lagostomus sp.•In this formation, Lagostomus is linked with paleosols and biological accumulations.