PBDB Collection

Arazati II (Miocene of Uruguay)

Where: San Jose, Uruguay (34.6° S, 57.0° W: paleocoordinates 34.6° S, 54.8° W)

• coordinate stated in text

• outcrop-level geographic resolution

When: Camacho Formation, Late/Upper Miocene (11.6 - 5.3 Ma)

• In Arazati the sediments of the Camacho Formation represent the first 2–5 m of the base of the cliffs and the exposed littoral platform at sea level (Perea and Martinez 2004; Sprechmann et al. 2000). Field observations indicate that the sediments continue into the Rio de La Plata, although the extent and thickness under the surface of the water are unknown (Sprechmann et al. 2000).

•* The said it's Huayquerian in age.

•

•Rinderknecht, et al. 2019: The mammalian fossil assemblage shows affinities with the upper Miocene Chasicoan and Huayquerian Ages/Stages of Argentina, especially with the one informally known as the “Mesopotamiense” (formerly considered as a Huayquerian local fossil fauna), of the Entre Ríos Province (Bostelmann & Rinderknecht, 2010; Brandoni, 2013; Mones & Rinderknecht, 2004; Perea et al., 1994; Perea, 2005; Perea et al., 2013; Rinderknecht et al., 2011; Vizcaíno et al., 2003).

•40Sr/39 Sr dated levels of the Paraná Formation and its southern correlative, the Puerto Madryn Formation (Scasso et al., 2001), renders a late Miocene 9.5 Ma–10 Ma (Tortonian) age for the top of the Paranean Sea in Argentina.

•Recently, the Camacho Formation was dated in 7.5–6 Ma. using Sr-isotope stratigraphy (del Río et al., 2018) or 11–9 Ma. (Soibelzon et al., 2019)

Environment/lithology: estuary or bay; lithified, sandy mudstone

• The sediments of the Camacho Formation are composed of conspicuous greenish gray friable and moderately compacted pelite that becomes greenish-brownish toward the top of the formation in its contact with the superposed Raigon Formation. This sedimentation episode probably represents a late Miocene transgressive event. The facies includes oyster patch reefs and incrusted ichnofossils such as Ophiomorpha nodosa and Thalassinoides sp. (Sprechmann et al. 1998, 2000), and vertebrates such as fishes, freshwater turtles, estuarine birds, and an abundant record of terrestrial mammals (Perea 2005). The holotype of A. castiglionii was recovered from the greenish sandy pelite a few meters above the shoreline of the Rio de la Plata in the Kiyu lithofacies of the Camacho Formation (Sprechmann et al. 2000).

Size class: macrofossils

• Posterior part of the skull (MNHN 2521), Right occipital region (MNHN 2521, reversed side), Right auditory region (MNHN 2521), Atlas (MNHN 2521), right P4–M3 (MNHN 2521)

Preservation: original phosphate

Collection methods: Specimen is located in the Museo Nacional de Historia Natural (MNHN), Montevideo, Uruguay.

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•Rinderknecht, et al. 2019: The studied specimen is housed in the Vertebrate Paleontological Collection of the Facultad de Ciencias, Departamento de Paleontología, Uruguay (FC-DPV)

Primary reference: A. Rinderknecht, E. Bostelmann, and M. Ubilla. 2011. New genus of giant Dinomyidae (Rodentia: Hystricognathi: Caviomorpha) from the late Miocene of Uruguay. Journal of Mammalogy 92(1):169-178 [C. Jaramillo/A. Cardenas ]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 152542: authorized by Carlos Jaramillo, entered by Andrés Cárdenas on 24.11.2013, edited by Juan Carrillo and Miranta Kouvari

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names

Mammalia
Placentalia -	Cetacea indet.², Litopterna sp.² Cetacea indet.² Brisson 1762 whale Litopterna sp.² placental
Rodentia -	Hystricognatha indet.² Hystricognatha indet.² rodent
Rodentia - Dinomyidae	Tetrastylus sp.², Arazamys castiglionii, Isostylomys laurillardi¹ Tetrastylus sp.² Ameghino 1886 caviomorph FC-DPV 2891 Arazamys castiglionii Rinderknecht et al. 2011 caviomorph Holotype Isostylomys laurillardi¹ Ameghino 1883 caviomorph MNHN 2187
Marsupialia -	Marsupialia indet.² Marsupialia indet.² marsupial

¹Rinderknecht et al. 2018; ²Rinderknecht et al. 2019