Arroyo Seco de la Frazada (Lower Section) (Miocene of Argentina)

Where: Mendoza, Argentina (34.9° S, 68.5° W: paleocoordinates 35.6° S, 63.2° W)

• coordinate estimated from map

When: Aisol Formation, Colhuehuapian (21.0 - 17.5 Ma)

• Forasiepi et al 2015: This contribution presents a new radiometric dating of a 19.480 ± 0.025 Ma tuff bed, which constrains the absolute age of the mammalian assemblage at these latitudes to the Early Miocene.

Environment/lithology: terrestrial; sandstone

• The lower section (LS) of the profile is composed mainly of medium to fine-grained sandstones predominantly grey, reddish, yellow, and less frequently pale green; the entire bed is roughly sub-horizontal. The sandstones are calcite-cemented and the entire bed has strong cross- stratification (Fig. 2), with higher angles towards the middle and upper parts of the section. Between the sandstones, levels of reddish to brownish, fine siltstones are interbedded. The thickness of the siltstone levels is larger towards the lower part of the section. In contrast, towards the upper part, reddish to greenish siltstones intraclasts are frequently found within the sandstones (Fig. 2). The intraclasts are variable in size and their surfaces are mostly rounded. Fossil wood and vertebrate remains are common in different parts of the LS. With the exception of the bones found in the siltstone, other material is highly eroded, showing signals of transportation and corrosion of biological organisms. In the area of the profile, the LS is approximately 15 m thick. The base, however, was not observed; it is covered by recent deposits.

Size class: macrofossils

Collection methods: Museo de Historia Natural de San Rafael, Mendoza, Argentina

Primary reference: A. M. Forasiepi, A. G. Martinelli, M. S. Fuente, S. Dieguez, and M. Bond. 2011. Paleontology and stratigraphy of the Aisol Formation (Neogene), San Rafael, Mendoza. Cenozoic Geology of the Central Andes of Argentina 135-154 [E. Vlachos/E. Vlachos]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 189519: authorized by Evangelos Vlachos, entered by Evangelos Vlachos on 25.10.2017, edited by Miranta Kouvari

Creative Commons license: CC BY (attribution)

Taxonomic list

Planopinae indet.
MHNSR-PV1028, partial skull
 Salientia -
Anura indet. Fischer von Waldheim 1813 frog
MHNSR-PV1074, isolated vertebra
 Testudines - Pantestudinidae
Chelonoidis sp. Fitzinger 1835 turtle
MHNSR- PV1064, femur of giant size
 Notoungulata - Toxodontidae
Palyeidodon cf. obtusum Roth 1898 notoungulate
MHNSR-PV1021, partial skull
Nesodon taweretus n. sp. Forasiepi et al. 2015 notoungulate
MHNSR-PV1004 (Figs. 6C and 6D) and probably MACN-PV18603
 Notoungulata - Hegetotheriidae
Hegetotherium sp. Ameghino 1887 notoungulate
right M3 and broken pieces of the postcranial skeleton (MNHSR-PV 1052; Fig. 7B)
 Notoungulata - Interatheriidae
Protypotherium sp. Ameghino 1882 notoungulate
left dentary with dentition (MHNSR- PV1050)
 Rodentia - Chinchillidae
Chinchillidae indet. Bennett 1833 chinchilid
MHNSR-PV1056, an euhypsodont, left M3
 Litopterna - Macraucheniidae
cf. Theosodon sp. Ameghino 1887 eutherian
additional metapods (e.g., MHNSR-PV253; MHNSR- PV1032), astragalus (MHNSR-PV1005), portions of tibia (e.g., MHNSR-PV1016, MHNSR-PV1017), and femora (e.g., MHNSR-PV1025, MHNSR-PV1020)