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The initial peopling of South America is a topic of intense archaeological debate. Among the most contentious issues remain the nature of the human-megafauna interaction and the possible role of humans, along with climatic change, in the extinction of several megamammal genera at the end of the Pleistocene. In this study, we present the analysis of fossil remains with cutmarks belonging to a specimen of Neosclerocalyptus (Xenarthra, Glyptodontidae), found on the banks of the Reconquista River, northeast of the Pampean region (Argentina), whose AMS 14C dating corresponds to the Last Glacial Maximum (21,090-20,811 cal YBP). Paleoenvironmental reconstructions, stratigraphic descriptions, absolute chronological dating of bone materials, and deposits suggest a relatively rapid burial event of the bone assemblage in a semi-dry climate during a wet season. Quantitative and qualitative analyses of the cut marks, reconstruction of butchering sequences, and assessments of the possible agents involved in the observed bone surface modifications indicate anthropic activities. Our results provide new elements for discussing the earliest peopling of southern South America and specifically for the interaction between humans and local megafauna in the Pampean region during the Last Glacial Maximum., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Del Papa et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The origin, affinity and paleoecology of macrofossils of soft-bodied organisms of the terminal Ediacaran Period have been highly debated. Previous discoveries in South America are restricted to small shelly metazoans of the Nama Assemblage. Here we report for the first time the occurrence of discoidal structures from the Upper Ediacaran Cerro Negro Formation, La Providencia Group, Argentina. Specimens are preserved in tabular sandstones with microbially-induced sedimentary structures. Flute marks and linear scours at the base of the sandstone layers indicate deposition under high energy, episodic flows. Stratigraphic, sedimentologic, petrographic and taphonomic analyses indicate that the origin of these structures is not related to abiotic process. Preservational and morphological features, as invagination and the presence of radial grooves, indicate that they resemble typical morphs of the Aspidella plexus. The large number of small-sized individuals and the wide range of size classes with skewed distribution suggest that they lived in high-density communities. The presence of Aspidella in the Cerro Negro Formation would represent the first reliable record of Ediacaran soft-bodied organisms in South America. It also supports the paleogeographic scenario of the Clymene Ocean, in which a shallow sea covered part of the southwest Gondwana at the end of the Ediacaran.

Pecoits et al. (Reports, 29 June 2012, p. 1693) describe bilaterian trace fossils and assign them an Ediacaran age based on the age of a granite interpreted as intrusive. We argue that the granite is not intrusive but in fact represents the basement of the sedimentary succession. Moreover, we show that identical trace fossils occur in nearby Carboniferous-Permian glacigenic rocks.

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The South American tetrapod track record is highly diverse and well known mainly from Argentina, Brazil, Bolivia, Chile and Peru. To date, many tracksites are known from Bolivia, most studied during the past century. From the Jurassic-Cretaceous La Puerta Formation of the Tunasniyoj locality (Incapampa-Icla syncline) thyreophoran trackways have previously been described. New geological studies related with the Central Atlantic Magmatic Province in Bolivia recognised the track-bearing unit as the Ipaguazú Formation, dated as Late Triassic in age. In this significantly new context, we present here a new track-bearing locality: Ruditayoj, neighbour to Tunasniyoj, near Icla, Chuquisaca, Bolivia. A detailed study of the trackways from this new site allowed new interpretations consistent with the geological context. Hundreds of Brachychirotherium trackways are present at the site with a wide diversity of preservational types. Behavioural issues such as gregariousness and grouping around ponds are suggested. Trackway parameters, track size and shape support large 'rauisuchid' or aetosaur pseudosuchian producers. Previous assignations to thyreophoran producers are discussed. This is the first record of Brachychirotherium from Bolivia, filling the lack of information about suchian fossils, well known in other South American sites. [ABSTRACT FROM AUTHOR]

In the Lago San Martín region (Santa Cruz Province, Argentina), the Springhill Formation (50-100 m thick) overlies the syn-rift El Quemado Complex, showing outcrops with wedge geometry. Four sedimentological sections were measured in the field, and three depositional palaeoenvironments were interpreted. The Springhill Formation starts with fluvial deposits, characterized by channel-fills and floodplains with palaeosol development, passing transitionally to a coastal plain and, finally, to marine sedimentation. The initial sandy transgressive deposits (Facies Association 9) are the main focus of this study, in which 10 ichnogenera ( Arenicolites, Bergaueria, Cylindrichnus, Diplocraterion, Macaronichnus, Palaeophycus, Planolites, Ophiomorpha, Rosselia and Skolithos) are described. Two ichnoassociations (foreshore and shoreface) were defined, and their distribution was controlled by the local palaeoenvironmental conditions, mainly energy, bathymetry and grain size of sediments. A highly bioturbated surface ( BI = 4) was recognized in Section 1 showing a limited occurrence and disappearing over short distances perpendicular to the palaeoshoreline. This surface shows a sharp sub-horizontal gently undulating top contact with a bioturbation thickness between 15 and 25 cm. This type of surface has limited usefulness as a key correlative surface, because it is spatially restricted in rift basins due to the tectonic activity, which creates high accommodation space rates. A more accurate characterization of the initial transgressive deposits of the Springhill Formation - which is the most important reservoir in southern Patagonia - could provide new ideas to solve problems in sub-surface studies. [ABSTRACT FROM AUTHOR]

A well preserved assemblage of organic-walled microfossils is described from the Alicia and Cerro Negro formations of the La Providencia Group. The microbiota is dominated by Leiosphaeridia species (L. minutissima, L. tenuissima, L. crassa and L. jacutica) and comprises colonial sphaeroids (Synsphaeridium sp.) and filamentous microfossils of the genus Siphonophycus. The assemblage is assigned to the Late Ediacaran Leiosphere Palynoflora (LELP), which is consistent with the occurrence of the discoidal fossil Aspidella (<565 Ma) in the overlying unit. The distribution of microfossils within the Alicia Formation is mainly controlled by the shallowing upward trend and thus, environmental factors. This is indicated by the abundance and size of filaments, which tend to occur near to the paleoshore in shallow water settings. Furthermore, large leiospheres also occur in shallower facies together with filaments, in accordance with existing models for acritarch ecology and distribution in the Proterozoic marine successions. The absence of acanthomorphic acritarchs is thus interpreted as a real evolutionary trend, and not as a result of preservational or environmental biases. Regarding the preservation of microfossils, a higher Thermal Alteration Index for the Alicia Formation, compared with older and younger units, is interpreted as a result of hydrothermal overprint and/or contact metamorphism by basic dikes. • La Providencia Group was accumulated around 600 and 550 Ma. • The first record of microfossils of Alicia Formation is described. • The main assemblage is assigned to Late Ediacaran Leiosphere Palynoflora. • Acritarchs confirm the paleoenvironmental conditions of this part of SW-Gondwana. • Aspidella supports a Late Ediacaran age for the sedimentary succession. [ABSTRACT FROM AUTHOR]

We present the first taphonomic analysis on basal sauropodomorph dinosaur remains from the Los Colorados Formation. We analyzed 22 bone samples with X-ray diffractometry, three of these in petrographic sections and one of them in SEM. In this article we recognize the taphonomic processes (biostratinomic and fossil-diagenetic) involved in the genesis of the 'La Esquina Local Fauna'. Regarding fossil diagenesis, it was possible to recognize the different processes that acted on the bone remains. In this sense, we analyzed different types of fracture present in the bones and their relationship with expansion generated by changes in the volume of minerals (for example, carbonates, gypsum and anhydrite). Finally, the importance of more taphonomic studies throughout the Los Colorados Formation is highlighted in order to better understand the vertebrate fossil record it contains. • Sauropodomorph bones were affected by different taphonomic processes. • At least three types of fractures associated with volume changes of minerals. • The fractures analyzed in the bones are of fossil-diagenetic origin. • The fossil record of vertebrate remains is found in well-developed overbank/floodplain deposits and rarely within fluvial channel facies. • Major bone loss can be explained by actual exhumation. [ABSTRACT FROM AUTHOR]

We present the first record of an extinct procyonid for Bolivia (Tariquía Formation, La Angostura, Santa Cruz de La Sierra; Late Miocene). It corresponds to Cyonasua , the first Carnivore taxon to enter South America from North America before the Paniamian Isthmus raised and as a part of the "proto Great American Biotic Interchange" (GABI). Cyonasua fossil record, comprises the temporal lapse late Miocene to early Pleistocene in several localities of Argentina, Venezuela and Uruguay. This genus encompasses ten formally named species: C. argentina , C. brevirostris , C. longirostris , C. pascuali , C. groeberi , C. lutaria , C. clausa , C. robusta , C. argentines , and C. meranii. The mandible and teeth preserved of the new specimen, YPFBLIT-PAL-020, allows us to assign it to Cyonasua cf. C. pascuali. This record reinforces the paleoenvironment with warm climates and humid environments with abundant water bodies, vegetation and trees proposed previously for Tariquia Fm. Also, the proposed Huayquerian Age for this Formation is supported by this record. • On this contribution we present the first record of an extinct procyonid for Bolivia (Tariquía Formation, La Angostura, Santa Cruz de La Sierra; Late Miocene). • It corresponds to Cyonasua, the first Carnivore taxon to enter South America from North America before the Paniamian Isthmus raised and as a part of the "proto Great American Biotic Interchange" (GABI). • Cyonasua fossil record, comprises the temporal lapse late Miocene to early Pleistocene in several localities of Argentina, Venezuela and Uruguay. • The mandible and teeth preserved of the new specimen, YPFBLIT-PAL-020, allows us to assign it to Cyonasua cf. C. pascuali. • This record reinforces the paleoenvironment with warm climates and humid environments with abundant water bodies, vegetation and trees proposed previously for Tariquia Fm. • Also, the proposed Huayquerian Age for this Formation is supported by this record. [ABSTRACT FROM AUTHOR]