Where: Madre de Dios, Peru (12.6° S, 70.1° W)

• Paleocoordinates: 12.0° S, 67.8° W (Wright 2013)

• coordinate stated in text

• hand sample-level geographic resolution

When: Ipururo Formation (Contamana Group), Chasicoan (10.0 - 9.0 Ma)

• From deposits atthe top ofthe Contamana Group (Kummel, 1948) [Solimoes Formation in Brazil (Moraes Rego, 1930; Caputo et al., 1971)], immediately below the Ucayali Unconfonnity separating the Contamana Group :from the overlyingMadredeDiosFormation(Oppenheim, 1946; CampbellandRomero-P., 1989). During the annual dry season, when the river is at its lowest, the fonnational contact is right at or just below the water line ofthe river (Fig. 8), thus it is difficult to determine with certainty the specific nature ofthe fossil-producing horizon, e.g., whether or not it might be a channel deposit and what its relationship to the underlying strata might be. The absence of data pertaining to the older Tertiary strata underlying the Ucayali Unconfonnity in this region precludes an unquestionable assignment ofthe horizon in question to a specific fonnation within the Contamana Group, although it is most probable that it lies within the Ipururo Fonnation (Kummel, 1948; Guizado, 1975; Pardo andZuñ:i.ga, 1976). PalaciosM. et al. (1996) refer to these beds as part of the Ipururo Group, citing Kummel (1948) as the source forthe denomination. However, Kummel (1948) referred onlyto an "IpururoF onnation" within the Contamana Group.

•The minimum age for the specimen is postulated to be at least ~9. 5 Ma, or late Miocene (Chasicoan SALMA; 12-9 Ma). This is based on the fact that the specimen comes from below the Ucayah Unconformity; a 40 ArP9 Ar date on a volcanic ash, the Cocama ash, :from above the Ucayali Unconfonnityis 9.01±0.28 Ma (Campbell et al., in press ). This ash date corroborates the prior interpretation that the faunas derived :from above the Ucayali Unconfonnity were late Miocene in age based on characteristic Huayquerian taxa (Fra:iley, 1986). Others, however, ha ve suggested that these faunasmight be older (e.g., Broin et al., 1993; Webb, 1995). The date for the Cocama ash indicates that these faunas are truly borderline as to whether they are Chasicoan or Huayquerian in age, but we conclude that they will probably pro veto be latest Chasicoan. The presence ofthe same taxa both abo ve and below the Ucayali Unconfonnity suggests that there might not be a huge time d1fference between faunas above and below the unconfonnity in all instances, although this might certainly be true in sorne instances. A more detailed discussion ofthe age ofthe fauna is presented below (see Geology).

Environment/lithology: wet floodplain; poorly lithified, silty siltstone and poorly lithified, muddy claystone

Size classes: macrofossils, mesofossils

Preservation: original phosphate

Collection methods: Repository: Paleontology collections of the Instituto Geologico, Minero, y Metalurgico de Peru

Primary reference: K. E. Campbell, C. D. Frailey, and L. Romero-Pittman. 2000. The Late Miocene Gomphothere Amahuacatherium peruvium (Proboscidea: Gomphotheriidae) from Amazonian Peru: Implications for the great american faunal interchange. INGEMMET, Boletin N. 23 1-127 [C. Jaramillo/A. Cardenas ]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 144515: authorized by Carlos Jaramillo, entered by Andrés Cárdenas on 09.05.2013

Creative Commons license: CC0 (CC0)