Genus Neoreomys Ameghino, 1887 TYPE SPECIES. — Neoreomys australis Ameghino, 1887 by original designation. REFERRED SPECIES. — Neoreomys australis (type species), Neoreomys huilensi s Fields, 1957, and Neoreomys pinturensis Kramarz, 2006. GEOGRAPHIC AND STRATIGRAPHIC DISTRIBUTION. — Pinturas and Santa Cruz formations (Early-Middle Miocene) in Chubut and Santa Cruz provinces (Bordas 1939; Kramarz 2006a; Kramarz et al. 2010; Arnal et al. 2019; Montalvo et al. 2019); Chinches Formation (late Early Miocene) in San Juan Province (López et al. 2011); Collón Curá Formation (Middle Miocene) in Chubut, Río Negro and Neuquén provinces (Bondesio et al. 1980; Vucetich et al. 1993); Río Frías Formation (Vucetich 1984), and Río Zeballos Formation (Pérez & Gonzáles Ruiz 2022) Chubut province; La Tiza Formation (Early Miocene), Neuquén Province, Argentina (Garrido et al. 2012). Cura-Mallín Formation (late Early-Middle Miocene) in Biobío Region, Pampa Castillo and Galera formations in Chile (Flynn et al. 2008; Solórzano et al. 2020; McGrath et al. 2022). La Victoria and Villavieja formations (Middle Miocene), in Huila Department, Colombia (Fields 1957; Walton 1997). REMARKS Neoreomys differs from Dasyprocta, Myoprocta, and Cuniculus in several characters of the skull and mandible (e.g., development and configuration of the masseteric crest, horizontal crest, notch for the insertion of the tendon of the masseter medialis pars infraorbitalis muscle; development of the bones that conform the zygomatic arch; convergence of the molar series; development of the maxillary and palatine bones in the palate). The crown of the cheek teeth of Dasyprocta and Myoprocta are much lower, and the occlusal surface is more complex than in Neoreomys (e.g., presence and development of lophs/ids; retention of fossettes/ids). Concerning Cuniculus and Capromys, the morphology of the occlusal surface differs from Neoreomys in terms of the depth of the flexi/flexids and the extension of the lophs/ids. The differences between Alloiomys and Neoreomys are detailed inVucetich (1977). Still, they can be highlighted: cheek teeth higher than in Neoreomys, a solid tendency to lamination, abundant cement, and dental series more convergent than in Neoreomys. The cheek teeth in Mesoprocta (Croft et al. 2011a) are higher than in Neoreomys and do not form roots. The flexus/ids and fossetes/ids disappear more quickly with wear and present a significant quantity of cement. Chubutomys and Phanomys differ from Neoreomys in the higher degree of hypsodonty, more ephimerous flexus/ids and fossetes/ids, and less thick enamel layer (see Pérez & Vucetich 2012; Pérez et al. 2012). On the other hand, Eocardia, Schistomys and Matiamys presents euhypsodonts cheek teeth (continuous growth without root formation) (see Pérez 2010).

Published as part of Urrea-Barreto, Francisco J., Link, Andrés, Carrillo, Juan D., Vanegas, Andrés, Perdomo, César A., Cooke, Siobhán B., Tallman, Melissa & Pérez, María E., 2023, Systematic revision of Neoreomys huilensis Fields, 1957 (Rodentia, Hystricognathi) from the Middle Miocene of La Venta (Villavieja, Colombia), pp. 721-737 in Geodiversitas 45 (25) on pages 726-728, DOI: 10.5252/geodiversitas2023v45a25, http://zenodo.org/record/10421982