The trophic structure of South American Late Pleistocene mammal communities has long posed an apparent energetic paradox: exceptionally high herbivore biomass combined with a scarcity of large carnivores and seemingly limited primary productivity. Here, this issue is re-examined using the Arroyo del Vizcaíno Local Fauna (Uruguay), an unusually rich and minimally time-averaged Lujanian assemblage dated to the end of Marine Isotope Stage 3. Population densities, standing crop biomass and energetic demands were estimated using established allometric relationships, with explicit treatment of uncertainty through sensitivity and Monte Carlo analyses. Under baseline assumptions of strict herbivory, herbivore energetic demand approaches the upper bounds of plausible primary productivity for Late Pleistocene southeastern South America, while prey biomass exceeds the energetic requirements of the sole large carnivore, Smilodon populator. Sensitivity analyses show that absolute energetic estimates depend strongly on physiological parameters, but the qualitative imbalance is robust across a wide parameter space. Introducing partial omnivory in ground sloths produces a marked reduction in herbivore demand for primary productivity and substantially narrows the apparent mismatch between herbivore biomass and carnivore demand. Even modest proportions of animal-derived energy (10–30

Several sites in the Americas are proposed to have evidence of human occupation before the Last Glacial Maximum (LGM). The timing of human colonisation of the Americas is a matter of debate due to its intrinsic interest, but also because of the implications of that arrival for the extinction of the megafauna. Here, we study a notable indentation in the right calcaneus of a giant extinct ground sloth Lestodon armatus from the Arroyo del Vizcaíno site, Uruguay, dated to 33 cal kyBP. We use a combination of 3D CT-scan modelling, high-resolution silicone casting, and microscopic wear and residue analysis to describe the morphology of the lesion, its associated residues, and the possible mechanisms behind its formation. Considering the indentation’s features, including its shape, depth, and the presence of organic residues, we argue that it could have been created by a penetrating object with a rounded tip, possibly a bone, ivory or hardened wood tip attached to a shaft. This evidence contributes to discussions on the dates of human arrival in South America and the potential interactions with the megafauna.

Understanding the role of megamammals in shaping terrestrial ecosystems and landscapes during the South American Late Pleistocene is crucial for estimating the impacts of extinctions on current ecological dynamics. Here, we aimed to investigate the mobility patterns and landscape use of the extinct giant ground sloth Lestodon armatus , a member of South America’s megafauna, where the Pleistocene extinction was the hardest. We report, to our knowledge, the first strontium isotope ratio ( 87 Sr/ 86 Sr) analysis for L. armatus , acquired from bone and dentin samples across six Uruguayan localities, including six individuals and serial sampling of a tooth from one of the sites. Our results show a highly localized 87 Sr/ 86 Sr signature for L. armatus in the study area, suggesting limited movement within a defined home range consistent with their body mass. These results rule out the existence of extensive seasonal migrations in this species. Finally, we complemented our isotopic results with a connectivity analysis to explore landscape connectivity in southern Uruguay during the Late Pleistocene. The results provide a baseline for studying the spatial ecology of megamammal communities in the region and expand the knowledge on how the extinction of large herbivores might have influenced landscape connectivity in South America during and after the Late Pleistocene.

This dataset consists of 3D digital models of fossilised remains from the Pleistocene megafauna of Uruguay, now publicly available for scientists, educators, and general public. The fossils, housed in collections across Uruguay, were digitised through photogrammetry, structured light, and CT scanning. The dataset includes models extinct species such as ground sloths, glyptodonts, mastodonts, and a sabre-toothed cat, which played significant roles in the Pleistocene ecosystems. The dataset is stored in the MorphoSource repository under an open licence, allowing for broad reuse research, education, and public outreach.

Since the publication of Megafauna: Giant Beasts of Pleistocene South America by Fariña et al. in 2013, much has been published on this fascinating subject. Here, we sum up those contributions according to their aim: taxonomic, geographical and phylogenetic novelty, new approaches to the natural history of those species, and extinction and its aftermath. The traditional centres of interest since the 19th century, especially the Río de la Plata region, have now been complemented as a source of information by many other regions in South America, and the remains are now being studied by biogeochemistry and molecular biology, as well as with finite element analysis and constantly refined statistics. Finally, scholars and the public are becoming more interested in the demise of the megamammals as the starting point of the current process of biodiversity loss.

The Megafauna3D project integrates advanced 3D scanning technologies and paleontological research to bring the extinct megafauna of Uruguay to formal and informal educational settings. Through the use of digitized fossil models, interactive education materials, and a web platform, the project engages the public and educational institutions in understanding the country’s paleontological heritage. This manuscript presents Megafauna3D’s multidisciplinary approach, its outreach initiatives, and the educational resources developed, such as 3D models and printed replicas, a book integrated with augmented reality, fanzines, and a teaching box. With a focus on open science, inclusivity, and accessibility, the project fosters public engagement with paleontological content and promotes fossil heritage conservation.

The study of fossils shows the changes through which life found its way from the original conditions of the primitive Earth to evolve from self-organized chemical reactions, to gathering in colonies, to gain from symbiosis as eukaryotes and to multicellular organisms. Since about 541 million years ago, fossils are found in great quantities, especially from marine environments (but also from other organisms), allowing us to study the sigmoidal growth of life, the turnover of evolutionary faunas and the catastrophic events called mass extinctions, which are also important lessons to deal with current processes of dwindling diversity.

The colonization of the pelagic realm by the vertebrates represents one of the major transitions in the evolutionary success of the group and in the establishment of modern complex marine ecosystem. It has been traditionally related with the Devonian rise of jawed vertebrates, but new evidences indicate that first active swimmers, invading the water column, occurred within earlier armoured jawless fishes ("ostracoderms"). These "primitive" fishes lacked conventional fish control surfaces and the precise mechanism used to generate lift and stabilizing forces still remains unclear. We show that, because of their shape, the rigid cephalic shield of Pteraspidiformes, a group of Silurian-Devonian "ostracoderms", generate significant forces for hydrodynamic lift. Particle Image Velocimetry and force measurements in a water channel shows that the flow over real-sized Pteraspidiformes models is similar to that over delta wings, dominated by the formation of leading-edge vortices resulting in enhanced vortex lift forces and delayed stall angles of attack. Additionally, experiments simulating ground effect show that Pteraspidiformes present better hydrodynamic performance under fully pelagic conditions than in a benthic scenario. This suggests that, lacking movable appendages other than the caudal fin, leading-edge vortices were exploited by earliest vertebrates to colonize the water column more than 400 Mya. Digital particle image velocimetry and force measurements in a water channel provide evidence that leading-edge vortices could be exploited by earliest vertebrates to colonize the water column more than 400 Mya.

Nutrient foramina are small openings in the periosteal surface of the mid-shaft region of long bones that traverse the cortical layer and reach the medullary cavity. They are important for the delivery of nutrients and oxygen to bone tissue and are crucial for the repair and remodeling of bones over time. The nutrient foramina in the femur’s diaphysis are related to the energetic needs of the femur and have been shown to be related to the maximum metabolic rate (MMR) of taxa. Here, we investigate the relationship between nutrient foramen size and body mass as a proxy to the aerobic capacity of taxa in living and extinct xenarthrans, including living sloths, anteaters, and armadillos, as well as extinct xenarthrans such as glyptodonts, pampatheres, and ground sloths. Seventy femora were sampled, including 20 from extant taxa and 50 from extinct taxa. We obtained the blood flow rate (Q̇) based on foramina area and performed PGLS and phylogenetic ANCOVA in order to explore differences among mammalian groups. Our results show that, among mammals, taxa commonly associated with lower metabolism like living xenarthrans showed relatively smaller foramina, while the foramina of giant extinct xenarthrans like ground sloths and glyptodonts overlapped with non-xenarthran placentals. Consequently, Q̇ estimations indicated aerobic capacities comparable to other placental giant taxa like elephants or some ungulates. Furthermore, the estimation of the MMR for fossil giant taxa showed similar results, with almost all taxa showing high values except for those for which strong semi-arboreal or fossorial habits have been proposed. Moreover, the results are compatible with the diets predicted for extinct taxa, which indicate a strong consumption of grass similar to ungulates and in contrast to the folivorous or insectivorous diets of extant xenarthrans. The ancestral reconstruction of the MMR values indicated a lack of a common pattern for all xenarthrans, strongly supporting the occurrence of low metabolic rates in extant forms due to their particular dietary preferences and arboreal or fossorial habits. Our results highlight the importance of considering different evidence beyond the phylogenetic position of extinct taxa, especially when extinct forms are exceptionally different from their extant relatives. Future studies evaluating the energetic needs of giant extinct xenarthrans should not assume lower metabolic rates for these extinct animals based solely on their phylogenetic position and the observations on their extant relatives.

El yacimiento del Arroyo del Vizcaíno en el sur de Uruguay presentamiles de restos fósiles de la megafauna sudamericana extinguida hace unosdiez mil años. Algunos de esos huesos muestran marcas que han sido asignadas a la acción de herramientas, una evidencia indirecta de presenciahumana a la inesperadamente alta edad de más de 30.000 años, duplicandolo que se aceptaba como la presencia humana más antigua del continenteamericano. Esta importancia y su propia riqueza fosilífera y taxonómica(con 16 especies diferentes), con un excepcional estado de conservación,y la base de estudios isotópicos y paleomoleculares realizados, nos hanpermitido emprender una amplia tarea de divulgación científica con visitasorganizadas, plataforma web y un libro de divulgación “Megafauna 3D: Unlibro de huesos”, entre otras actividades que aquí se detallan.

Not so long ago, huge mammals weighing more than 1,000 kg existed practically all over the world. We call these giants the Pleistocene megafauna because they lived in a time period called the Pleistocene and were almost completely extinct around 11,700 years ago. These mammals lived on Earth for millions of years and were very important to almost all land-based ecosystems. However, natural climate change and humans decreased their ability to survive. Today, we find fossils of Pleistocene megafauna all over the world, including bones, hair, droppings, and even footprints. Scientists dig for these fossils to learn more about these animals and why they went extinct. Studying these ancient animals also gives scientists important information that helps them understand the risks that today’s living animals face in our world.

We report fossil mammal burrows from backshore beach facies in the Camacho Formation of southern Uruguay, of Late Miocene (Huayquerian SALMA) age. The presence of desiccation cracks and rhizoliths indicate the occurrence of relatively extended periods of subaerial exposure and the incipient development of vegetation. The analysis of the burrows' spatial extent, size, and structure reveals the existence of exceptionally well-preserved and intercrossing tunnel systems. We show the existence of different size classes of burrows, which indicate that at least four different taxa were responsible for their construction. Considering the inferred body masses of the trace makers obtained from allometric relationships and the body masses of taxa recovered for the Camacho Formation, the burrows may have been produced by a combination of the following mammals: one of several rodents, notoungulates, cingulates, folivorans, and a carnivoran. The fossil association represents an exceptional case of a community of ecosystem engineers in the Late Miocene of southeastern South America.

The analysis of stable isotopes on fossil mammals has become a widely used tool for understanding the paleoecology and paleodiet of these organisms. In this work, we study the stable isotope composition of collagen (δ13C and δ15N) and bioapatite (δ13C and δ18O) of fossil bones from Arroyo del Vizcaíno, a fossiliferous site in southern Uruguay dated to ∼32 ka cal BP. Fourteen taxa were analyzed: the ground sloths Lestodon armatus, Glossotherium robustum, Mylodon darwinii, Valgipes bucklandi and Nothrotheriops sp.; the glyptodonts Glyptodon reticulatus, Panochthus tuberculatus, and Doedicurus clavicaudatus; the equids Hippidion principale and Equus neogeus; the proboscidean Notiomastodon platensis; the notoungulate Toxodon platensis; the saber-tooth felid Smilodon populator; and an indeterminate cervid. In general, the percentage of nitrogen in collagen and the C:N ratio were within the limits expected for collagen preservation in fossil bone. The δ13C and δ15N results of the herbivores indicated that most taxa consumed high proportions of C3 plants in open, relatively dry environments, but significant variations were observed. Furthermore, relatively high values of δ18O in bone bioapatite, which approximately tracks local drinking water, indicated low precipitation and/or high evaporation. Our results show that the herbivorous taxa present at the site covered a considerable range of the grazer-browser spectrum and support the existence of niche partitioning among closely related taxa. Overall, these kinds of approaches are indispensable to better understand how these communities thrived during the Pleistocene in the region, supporting an outstanding number of giant species, before their extinction at the Pleistocene-Holocene transition.

Sloths are represented today only by two distantly-related small, arboreal, and folivorous genera. However, the fossil record of the clade is composed of many more taxa, with much more diverse morphologies, including giant terrestrial forms with no clear modern analogs. In this context, several approaches have been implemented in order to explore the ecological adaptations of fossil taxa and, in particular, their dietary preferences. In this work we used 3D Finite Elements Analysis (FEA) coupled with Geometric Morphometrics (GMM) to explore the ecomorphology of sloths and possible differences among taxa related to dietary adaptations. Digital models of the mandibles of 14 taxa were obtained (two extant and twelve extinct), representing members of all the major clades within the group. We modeled the actions of the three major muscles involved in mastication (masseter, temporalis, and pterygoideus) and simulated unilateral mastication in four different conditions, one for each tooth along the toothrow. The results were analyzed qualitatively regarding the distribution of von Mises stress (vMs) and quantitatively using the mesh-weighted arithmetic mean (MWAM) vMs, strain energy (SE), and mechanical efficiency (ME). Differences in the distribution of high-vMs areas and lower SE values were found among taxa predicted to be grazers in comparison to those predicted to be browsers. Furthermore, when simulating biting with the most anterior tooth, we observed considerably higher vMs and SE values in taxa with a caniniform, which could indicate its involvement in sexual display rather than in food processing, acquisition, or other strenuous activities.

Sloths represent one of the most successful South American clades that reached North America during the Great American Biotic Interchange (GABI). At least four families are known from the Pleistocene of North America: Mylodontidae, Megalonychidae, Megatheriidae, and Nothrotheriidae. Members of the Nothrotheriidae are known from the Middle Miocene to the Pleistocene/Holocene transition in the Americas, but Nothrotheriops is the only genus in the family recorded in North America. Recently, femora with characteristic nothrothere morphology were recovered from Santa Fe, Argentina, and assigned to Nothrotheriops , thus greatly expanding the geographic distribution of this taxon. In Uruguay, records of Quaternary Nothrotheriidae are scarce, and previous reports are limited to the genus Nothrotherium . In this work, we describe a humerus from Arroyo del Vizcaíno (AdV), a ~30 ka site located in southern Uruguay, and assign it to the nothrotheriid Nothrotheriops sp. We also discuss several specimens from Uruguay originally assigned to Nothrotherium , which upon re-examination can be tentatively reassigned to Nothrotheriops sp. Furthermore, we employ stable isotope analysis to explore the climatic and dietary preferences of this taxon in South America. The new records are consistent with the materials reported from Argentina, thus providing new knowledge of the geographic distribution of the taxon, as well as its climatic and dietary preferences. Stable isotope results showed δ 13 C values consistent with diets based mainly on C 3 plants, similar to those published for N. shastensis in North America.

ABSTRACT With the excuse of writing a critique to Domínguez-Rodrigo et al. (2021, duly replied here: Domínguez-Rodrigo & Baquedano, 2022), Holcomb et al. (this volume) intend to deny the proposal that the Arroyo del Vizcaíno (AdV, Fariña et al. 2014) is a site with evidence of human presence in South America before the LGM. Among the flaws of their critique, it must be mentioned that they decide to utterly ignore a few lines of evidence that sustain the questioned hypothesis (mortality profile of the individuals of the megafauna found there, representation of their anatomical regions, relative proportions of the Voorhies groups, etc.), state misled interpretation of the chronology and stratigraphy, refuse to accept the presence of human-modified lithics and show also non-acceptance of the conclusions of our thorough study of the key evidence, the cut-marks (Fariña et al. 2014, Fariña 2015, Domínguez-Rodrigo et al. 2021), based on a purported ideal of how a site should be researched, which leave aside those that point out at different conclusions from theirs.

Mylodontidae (Mammalia, Xenarthra) is a family of ground sloths widely distributed in the South American fossil record, with members also present in Central and North America. Within the Mylodontidae, Lestodon armatus is the largest species, with an estimated body mass of more than three tonnes. This work focuses on the enlarged lower caniniforms of L. armatus as possibly exaggerated sexually dimorphic structures. Lower caniniforms from the late Pleistocene of Argentina, Uruguay, and Bolivia were studied using specimens from seven palaeontological collections. The possible sexual dimorphism in the caniniforms and its implications regarding the existence of sexual selection was assessed through morphometric analyses. The results support the existence of sexual dimorphism in L. armatus. Sexual dimorphism in an exaggerated structure in a large mammal suggests the existence of sexual selection, via competition between males or female mate choice, resulting in the evolution of the dimorphic structure. In L. armatus, the enlarged caniniforms would correspond to males and could have functioned as armaments in intraspecific fights or ornaments for sexual display. Based on observations in extant mammals, a polygynous mating system is proposed as highly probable in L. armatus, although the existence or composition of social groups cannot be certainly determined.

The extinct Gomphotheriidae is the only proboscidean family that colonized South America. The phylogenetic position of the endemic taxa has been through several revisions using morphological comparisons. Morphological studies are enhanced by paleogenetic analyses, a powerful tool to resolve phylogenetic relationships; however, ancient DNA (aDNA) preservation decreases in warmer regions. Despite the poor preservation conditions for aDNA in humid, sub-tropical climates, we recovered ∼3,000 bp of mtDNA of Notiomastodon platensis from the Arroyo del Vizcaíno site, Uruguay. Our calibrated phylogeny places Notiomastodon as a sister taxon to Elephantidae, with a divergence time of ∼13.5 Ma. Additionally, a total evidence analysis combining morphological and paleogenetic data shows that the three most diverse clades within Proboscidea diverged during the early Miocene, coinciding with the formation of a land passage between Africa and Eurasia. Our results are a further step toward aDNA analyses on Pleistocene samples from subtropical regions and provide a framework for proboscidean evolution.

With eight species, Panochthus is one of the most abundant and diverse glyptodont genera during the Pleistocene of South America, as well as one of the largest glyptodonts. The relationship between the shape of the tube and its usage as weapons in the species of Panochthus is explored here; moreover, we intend to assess how they evolved among the species of the genus Panochthus. The morphology of the caudal tube is: (1) approximate to conical-cylindrical and (2) hilt-less Viking style sword. The form (1) is represented in P. subintermedius from Early Pleistocene - Middle Pleistocene (Ensenadan). The form (2) is present in the specimens from the Middle - Late Pleistocene (Bonaerian-Lujanian): P. tuberculatus, P. greslebini, P. florensis. P. intermedius, P. frenzelianus, P. jaguaribensis and P. hipsilis is not considered. The shape of the caudal tube (1) allows the glyptodont to perform its blows more effectively in all directions; which implies hitting with less precision. Whereas, the form (2) style of Viking sword, has the greater effectiveness in the blows delivered in a horizontal movement that requires greater accuracy. In the more recent species of Panochthus, those that show the form (2) present also more ornamentations that were possibly covered by corneous structures.

The earliest widely accepted presence of humans in America dates to approximately 17.5 cal kyr BP, at the end of the Last Glacial Maximum (LGM). Among other evidence, this presence is attested by stone tools and associated cut-marks and other bone surface modifications (BSM), interpreted as the result of the consumption of animals by humans. Claims of an older human presence in the continent have been made based on the proposed anthropogenic modification of faunal remains; however, these have been controversial due to the highly subjective nature of the interpretations. Here, we employ advanced deep learning algorithms to objectively increase the accuracy of BSM identification on bones. With several models that exhibit BSM classification accuracies greater than 94%, we use ensemble learning techniques to robustly classify a selected sample of BSM from the approximately 30 kyr BP site of Arroyo del Vizcaíno, Uruguay. Our results confidently show the presence of cut-marks imparted by stone tools on bones at the site. This result supports an earlier presence of humans in the American continent, expanding additional genetic and archaeological evidence of a human LGM and pre-LGM presence in the continent.