Telen (Melchor, 2000) (Miocene of Argentina)

Where: La Pampa, Argentina (36.3° S, 65.5° W: paleocoordinates 36.5° S, 63.3° W)

• coordinate stated in text

When: Cerro Azul Formation, Huayquerian (9.0 - 6.8 Ma)

• The Cerro Azul Formation crops out in most of La Pampa Province, except in the southern region (Linares et al., 1980). It is a continental, nearly flat-lying unit composed of massive, pale red to pinkish siltstones and fine-grained sandstones with interbedded, poorly developed palaeosols (e.g., Linares et al., 1980; Goin et al., 2000). This lithostratigraphic unit is considered the distal portion of a clastic wedge related to the late Cenozoic Andean fold and thrust belt that is well developed in the neighbouring Mendoza Province. The maximum outcropping thickness is about 40 m, although the exposures are generally less than 5 m thick. The Cerro Azul Formation has yielded numerous vertebrate remains, specially mammals, which are referred to the Huayquerian land mammal age, which is of late Miocene age (Pascual and Bondesio, 1982; Montalvo and Casadío, 1988; Goin et al., 2000; Verzi et al., 1991, 1994, 1995, 1999, 2003, 2004; Montalvo et al., 1995, 1996, 1998; Esteban et al., 2001; Cerdeño and Montalvo, 2001, 2002). The base of the Cerro Azul Formation is covered and its top is overlain by Pliocene and younger (mostly aeolian) sediments or is composed of a discontinuous calcrete crust that forms a resistant layer responsible for the preservation from erosion of the unit. In the subsurface, the unit reaches ~370 m thick overlying older Cenozoic sediments or basement rocks (De Elorriaga and Tullio, 1998).

•Schmidt et al. 2018: Figure 2 illustrates the stratigraphic distribution of the locality giving a general age estimate of 7.2-7.5Ma

Environment/lithology: "floodplain"; lithified, paleosol/pedogenic, brown, gray, calcareous siltstone and lithified, fine-grained sandstone

• The recovered fauna, notoungulates and rodents specially, is indicative of steppes or herbaceous plains. Particularly, the hegetotheriid Paedotherium minor (Notoungulata) was a typical dweller of these environments in dry to humid warm climates (Bond et al., 1995), very abundant in this region during the late Miocene (Zetti, 1972; Cerdeño and Bond, 1998; Montalvo, 2004).

•Schmidt et al. 2018: Deposits at Telen, Bajo Giuliani, El Guanaco and Caleufú were interpreted as loess-like deposits with immature palaeosols and little diagenetic alteration

• The lithology of the section is monotonous, and mostly composed of carbonate-cemented greyish orange pink (5 YR 7/2) siltstones and fine-grained sandstones. The distinction of horizons in the soil profiles is poor and the stacked palaeosols are 1.7 m (lower) and 1.9 m (upper) thick. Both palaeosols are separated by a 2 to 7 cm thick, discontinuous bed of laminated, greyish-pink mudstone with mudcracks. Beneath the lower palaeosol lies a 0.5 m thick interval with poor pedogenic modification, which is a siltstone with abundant glass shards and no carbonate cementation. Each palaeosol exhibits a 1.2 to 1.4 m thick interval with greater carbonate cementation that is considered as a calcic horizon. The upper soil profile shows a second uppermost horizon, 0.30 m thick, more clayey than the rest of de soil, with fine prismatic peds and Celliforma isp. (fossil bee cell). Most conspicuous features of both palaeosols include pervasive (although not uniform) carbonate (micritic calcite) cementation, pedogenic slickensides and clastic dykes. Carbonate cementation is not homogeneous in the section. Calcium carbonate content is minimum (~1%) in the lower part of each palaeosol, increasing upward (~10%). At the field, carbonate cement appears as calcareous concretions with dominantly sub-vertical arrangement (up to 15 cm long and 5 cm diameter) and scarce nodules (1 to 2 cm in diameter). Pedogenic slickensides constitute curved, striated, clayey surfaces with a circular roughly concentric arrangement in plan view and a conical 3D pattern. These structures are 0.2 to 0.7 m in diameter and 1 m deep. Clastic dykes are 1 to 7 cm thick, sub-vertical, and filled by two to four pairs of symmetrical muddy laminae showing subtle lithology and colour contrasts. The classic dykes show no preferred orientation.

Size classes: mesofossils, microfossils

Preservation: original phosphate

Collection methods: bulk, sieve,

• The collection includes all materials from surface prospecting. The low gradient of the modern margin of the depression favoured the erosive action by physical processes that loosened the fossils from the host material. For this reason, bone remains are frequently found in small concentrations produced by running water during rains. During a single visit to the site, 1955 specimens were recovered, 94.53% of them loose, and just 5.47% within the host material. Both the loose and in situ remains appeared throughout the exposed surface of the two palaeosol levels, randomly distributed, disarticulated and dispersed. The in situ material was found scattered in the host siltstone as well as in calcite concretions.

Primary reference: C. I. Montalvo, R. N. Melchor, G. Visconti and E. Cerdeño. 2008. Vertebrate taphonomy in loess-palaeosol deposits: A case study from the late Miocene of Central Argentina. Geobios 41:133-143 [C. Jaramillo/A. Cardenas ]more details

Purpose of describing collection: taphonomic analysis

PaleoDB collection 152061: authorized by Carlos Jaramillo, entered by Andrés Cardenas on 05.11.2013, edited by Grace Varnham

Creative Commons license: CC BY (attribution)

Taxonomic list

• No complete skulls or skeletons were found in the studied assemblage. The whole recovered sample comprises 11,647 pieces, including 5598 anatomically and taxonomically iden- tified remains, and 6049 undetermined fragments, mostly splinters. Taxonomically determined remains include 1277 isolated postcranial elements attributed to undeterminable Mammalia, 23 to undeterminable Aves, 2894 scutes of xenarthran carapaces, and five tortoise scutes. Besides, there are 1396 cranial elements (including isolated teeth) assigned to different mammal taxa and three to Teiidae reptiles.
Reptilia
 Testudines - Panchelidae
Chelidae indet. sideneck turtle
1 specimen
Aves
  -
Aves indet. Linnaeus 1758 bird
7 specimens
Reptilia
 Squamata -
Tupinambis sp. Daudin 1802 tegu
1 specimen
Mammalia
 Notoungulata - Hegetotheriidae
Paedotherium minor Cabrera 1937 notoungulate
120 specimens
 Notoungulata - Mesotheriidae
Mesotheriinae indet. Alston 1876 notoungulate
6 specimens
 Rodentia - Chinchillidae
Lagostomus sp. Brookes 1828 viscacha
14 specimens
 Rodentia - Dinomyidae
Tetrastylus sp. Ameghino 1886 caviomorph
1 specimen
 Rodentia - Caviidae
Caviidae indet. Gray 1821 caviomorph
16 specimens
Dolicavia sp. Ameghino 1916 caviomorph
4 specimens
Palaeocavia sp. Ameghino 1889 caviomorph
18 specimens
 Rodentia - Octodontidae
Octodontidae indet. Waterhouse 1839 caviomorph
3 specimens
 Rodentia - Abrocomidae
Protabrocoma sp. Kraglievich 1927 chinchilla rat
13 specimens
 Rodentia - Echimyidae
Echimyidae indet. Gray 1825 spiny rat
1 specimen
Pampamys emmonsae Verzi et al. 1995 spiny rat
3 specimens
Reigechimys cf. plesiodon Verzi et al. 1994 spiny rat
7 specimens
Theridomysops parvulus Rovereto 1914 spiny rat
1 specimen
 Rodentia - Ctenomyidae
Ctenomyidae indet. Lesson 1842 caviomorph
4 specimens
 Carnivora - Procyonidae
Cyonasua sp. Ameghino 1885 procyonid carnivore
2 specimens
 Cingulata - Dasypodidae
Proeuphractus sp. Ameghino 1886 armadillo
1 specimen
Proeuphractus limpidus Ameghino 1886 armadillo
1 specimen
Euphractini indet. Winge 1923 armadillo
1 specimen
Chorobates villosissimus Reig 1958 armadillo
1 specimen
Macroeuphractus scalabrini armadillo
1 specimen
Macroeuphractus morenoi Rovereto 1914 armadillo
1 specimen
Vetelia perforata Scillato-Yané 1977 armadillo
1 specimen
Doellotatus inornatus Rovereto 1914 armadillo
1 specimen
Chasicotatus ameghinoi Scillato-Yané 1977 armadillo
1 specimen
 Xenarthra - Mylodontidae
Mylodontidae indet. Ameghino 1889 edentate
1 specimen
Elassotherium sp. Cabrera 1939 edentate
1 specimen
 Xenarthra -
Coscinocercus sp. Cabrera 1939 edentate
1 specimen
Aspidocalyptus sp. Cabrera 1939 edentate
1 specimen
Hoplophractus sp. Cabrera 1939 edentate
1 specimen
 Xenarthra - Panochthidae
Hoplophorus sp. Lund 1838 edentate
1 specimen
 Ungulata -
Litopterna indet. eutherian
3 specimens
 Ungulata - Proterotheriidae
Proterotheriidae indet. Ameghino 1887 eutherian
cf. Brachytherium cuspidatum Ameghino 1883 eutherian
 Sparassodonta - Borhyaenidae
Borhyaenidae indet. Savage 1951 metatherian
1 specimen
 Polydolopimorphia - Argyrolagidae
Argyrolagidae indet. Ameghino 1904 metatherian
1 specimen
 Didelphimorphia - Didelphidae
Didelphinae indet. Gray 1827 opossum
2 specimens
Thylatheridium sp. Reig 1952 opossum
1 specimen
Thylatheridium dolgopolae Reig 1952 opossum
1 specimen
Thylatheridium hudsoni Goin and Montalvo 1988 opossum
1 specimen
Hyperdidelphys pattersoni Reig 1952 opossum
2 specimens
 Didelphimorphia - Sparassocynidae
Sparassocynidae indet. Reig 1958 marsupial
1 specimen