PBDB Collection

MD-67 (Miocene to of Peru)

Where: Cuzco, Peru (12.7° S, 71.3° W: paleocoordinates 13.4° S, 67.5° W)

• coordinate stated in text

• outcrop-level geographic resolution

When: Yahuarango Formation, Burdigalian to Burdigalian (20.4 - 13.8 Ma)

• The fossiliferous outcrop dips 35 SW with a N130 strike. It crops out in the southern flank of the Pantiacolla anticline and was originally mapped as part of the PaleoceneeEocene Yahuarango Formation, based on sedimentary facies, but without any biostratigraphic constraint (Vargas and Hipólito, 1998). The Yahuarango Formation (northern Perú) is poorly dated and it consists mainly of red siltstones and mudstones forming distal fluvial deposits (see Roddaz et al., 2010 for a review).

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•Antoine et al., 2013: Apatite Fission Track provides a detrital age (17.1 ± 2.4 Ma) for the vertebrate-yielding locality, slightly older than its inferred biochronological age (Colloncuran-early Laventan South American Land Mammal Ages: ∼15.6–13.0 Ma). Be as it may, the middle Miocene age of the concerned outcrop is fully contradictory to its original assignment to the Paleocene-Eocene Yahuarango Formation (Vargas and Hipólito, 1998).

Environment/lithology: wet floodplain; lithified, red, silty siltstone and lithified, red, muddy mudstone

• Lithology of the fossil-bearing beds (i.e., channel-iron deposits, with Fe-rich pisolite gravels) provides valuable information on the depositional environment and associated diagenetic processes: pisolites might have formed in the ground by alteration and concretion of highly ferruginous groundwater solutions under warm, humid, and seasonally-contrasted conditions (Tardy, 1992). Accordingly, isotopic analyses performed on coeval mollusc shells from the Iquitos area (w1000 km more to the North) show the region was experiencing a seasonal water influx under a monsoonal-like tropical climate by that time (Kaandorp et al., 2006; Wesselingh et al., 2006). Both proxies are therefore in good agreement.

•One of the striking features of the Miocene of Amazonia is the presence of a large and long-lasting “mega-wetland”. The Amazonian mega-wetland reached its maximum extent during the Middle Miocene (also called “Pebas phase” sensu Hoorn et al., 2010) and it consisted of a complex mosaic of lakes, embayments, swamps, rivers, and fluvio-tidal environments (see review in Hoorn et al., 2010). Our data suggest the absence of this megawetland in the Amazonian Madre de Dios Subandean Zone of Perú (Fig. 4), while other coeval localities such as IQ-26 and NA069 (nearby Iquitos; Antoine et al., 2006; Pujos et al., 2009) or the Fitzcarrald Local Fauna (Antoine et al., 2007; Goillot et al., 2011) were under its influence during the same period (Fig. 4). This environmental contrast might in turn have played some role in the faunal discrepancies as observed in middle Miocene times between Northern and Southern South America (Madden et al., 1997).

• The Yahuarango Formation (northern Perú) is poorly dated and it consists mainly of red siltstones and mudstones forming distal fluvial deposits (see Roddaz et al., 2010 for a review).

Size classes: macrofossils, mesofossils

Preservation: original phosphate

Collection methods: Repository: Museo de Natural de la Uni- versidad Nacional Mayor San Marcos, Lima, Perú

Primary reference: P. O. Antoine, M. Roddaz, S. Brichau, J. Tejada-Lara, R. Salas-Gismondi, A. Altamirano, M. Louterbach, L. Lambs, T. Otto and S. Brusset. 2013. Middle Miocene vertebrates from the Amazonian Madre de Dios Subandean zone, Peru. Journal of South American Earth Sciences 42:91-102 [C. Jaramillo/A. Cardenas ]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 144513: authorized by Carlos Jaramillo, entered by Andrés Cárdenas on 09.05.2013, edited by Kateryn Pino

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names

Mammalia
Sparassodonta -	Sipalocyon sp. Sipalocyon sp. Ameghino 1887 metatherian
Didelphimorphia - Didelphidae	"Marmosa cf. laventica" = Micoureus laventicus "Marmosa cf. laventica" = Micoureus laventicus Marshall 1976 woolly mouse opossum
Rodentia - Dinomyidae	Scleromys sp. Scleromys sp. Ameghino 1887 caviomorph
Rodentia - Acaremyidae	Acaremyidae indet. Acaremyidae indet. Wood 1949 caviomorph
Rodentia -	Nuyuyomys chinqaska, Guiomys sp. Nuyuyomys chinqaska Boivin et al. 2021 caviomorph Guiomys sp. Pérez 2010 caviomorph
Cingulata - Glyptodontidae	Glyptodontinae indet. Glyptodontinae indet. Gray 1869 glyptodon