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Macrofossils, Boivin et al. (2021): These levels were originally mapped as belonging to the lower member of Ipururo Formation (middle Miocene in age in the Huallaga basin) [Antoine et al. 2021], an assignation in agreement with the nature of their facies and depositional environment sequence. The fossil content of the TAR-31 encompasses plants, amber clasts, crabs, chondrichthyans, osteichthyans, anurans, chelonians, crocodylomorphs, birds, and mammals (including metatherians, xenarthrans, liptoterns, notungulates, sirenians, chiropterans, primates, and caviomorph rodents). The TAR-31 mammal assemblage includes a didelphid marsupial (currently under study by one of us, NSS), the interatheriine notoungulate Miocochilius sp., the didolodontid Megadolodus sp., the platyrrhine primate Neosaimiri aff. fieldsi [Marivaux et al. 2020], and the caviomorph fauna described here (see ‘Age of TAR-31’ section of this present work). This assemblage recalls some of the Laventan SALMA localities: Quebrada Honda in Bolivia (13.112.2 Ma) [Gibert et al. 2020], the Fitzcarrald local fauna in SE Peru [Tejada-Lara et al. 2015], and especially the lower part of the Villavieja Formation in the La Venta area in Colombia (13.8–11.6 Ma; [Flynn et al. 1007] and see above). Accordingly, the TAR-31 locality most likely documents the late middle Miocene Laventan SALMA [Marivaux et al. 2020]., Boivin et al. (2021): TAR-31 consists of a 10–15 cm-thick yellow microconglomerate interbedded within a grey cross-stratified and sandstone-dominated fluvial unit (Fig 2A [Marivaux et al. 2020]). The latter is intercalated between thick violin-grey variegated paleosols pointing to the existence of a meandering river with a sustainable floodplain [Marivaux et al. 2020]. |