Megatherium Research Articles

More than fossils: Paleoburrows as geoheritage and paleoenvironmental archives in the Caminhos dos Cânions do Sul UNESCO Global Geopark, Southern Brazil

The paleoburrows (paleotocas) are ichnofossils produced by the autochthonous megafauna of South America. The Caminhos dos Cânions do Sul UNESCO Global Geopark (CCSUGG), Southern Brazil, contains a large amount of these ichnofossils, which are regarded as internationally relevant. This article aims to discuss paleoburrows as geoheritage and paleoenvironmental records, using the examples present in the CCSUGG. For this purpose, bibliographic research, paleoburrows cataloguing fieldwork and mapping routine were carried out. So far, 24 paleoburrows have been compiled. Mostly found in sedimentary friable rocks, such as the Botucatu Formation sandstones, can also occur in harder, weathered lithologies in a smaller amount. Some bioerosive structures show claw scrapping and digging signs, attributed to the Pliocene-Pleistocene South American megafauna, such as the giant sloths and the giant armadillos. Despite these 24 paleoburrows, four of them are recognized as geosites of regional and international value. These ichnofossils provide geological and paleontological values, considering their builders are already extinct and their presence allows to infer paleoenvironmental changes and megamammals distributions. Besides tangible values, these burrows evoke myths and histories about indigenous people and settlers who used these burrows as shelter, representing intangible cultural heritage. Even though these values, paleoburrows face threats that endanger their conservation, like unguided visitors, water flow and block falls. Hence, there are geoeducational efforts to preserve these ichnofossils for future generations. All these processes are evident in geosites with scientific, scenic and touristic values, the paleotocas giant paleoburrows.

Anthropogenic modification of a giant ground sloth tooth from Brazil supported by a multi-disciplinary approach

Identifying evidence of human modification of extinct animal remains, such as Pleistocene megafauna, is challenging due to the similarity of anthropogenic and non-anthropogenic taphonomic features observed under optical microscopy. Here, we re-investigate a Late Pleistocene ground sloth tooth from northeast Brazil, previously suggested as human-modified based only on optical observation. To characterize the macro- and micro-morphological characteristics of the marks preserved in this tooth and evaluate potential human modification, we used stereomicroscope and scanning electron microscopy (SEM) supplemented by energy dispersive spectroscopy (EDS), UV photoluminescence (UV/PL), synchrotron-based X-ray fluorescence (SR-XRF), and synchrotron micro-computed tomography (SR-µCT). These methods allowed us to discriminate non-anthropogenic taphonomic features (root and sedimentary damage), anthropogenic marks, and histological features. The latter shows the infiltration of exogenous elements into the dentine from the sediments. Our evidence demonstrates the sequence of anthropogenic and non-anthropogenic taphonomic modification of this tooth and supports its initial intentional modification by humans. We highlight the benefits of emerging imaging and spectral imaging techniques to investigate and diagnose human modification in fossil and archaeological records and propose that human modification of tooth tissues should be further considered when studying possibly anthropogenically altered fossil remains.

Deep-learning-enabled antibiotic discovery through molecular de-extinction.

Molecular de-extinction aims at resurrecting molecules to solve antibiotic resistance and other present-day biological and biomedical problems. Here we show that deep learning can be used to mine the proteomes of all available extinct organisms for the discovery of antibiotic peptides. We trained ensembles of deep-learning models consisting of a peptide-sequence encoder coupled with neural networks for the prediction of antimicrobial activity and used it to mine 10,311,899 peptides. The models predicted 37,176 sequences with broad-spectrum antimicrobial activity, 11,035 of which were not found in extant organisms. We synthesized 69 peptides and experimentally confirmed their activity against bacterial pathogens. Most peptides killed bacteria by depolarizing their cytoplasmic membrane, contrary to known antimicrobial peptides, which tend to target the outer membrane. Notably, lead compounds (including mammuthusin-2 from the woolly mammoth, elephasin-2 from the straight-tusked elephant, hydrodamin-1 from the ancient sea cow, mylodonin-2 from the giant sloth and megalocerin-1 from the extinct giant elk) showed anti-infective activity in mice with skin abscess or thigh infections. Molecular de-extinction aided by deep learning may accelerate the discovery of therapeutic molecules.

The metamorphosis of the Megatherium: Examples of Goethe's heterodox palaeontology

In this paper I present the well-known German literary giant Johann Wolfgang von Goethe (1749–1832) as a heterodox thinker in palaeontology. In Britain, Goethe is best known as a poet, playwright and man of letters, despite producing substantial and detailed scientific studies to which he occasionally attached highly controversial interpretations. In his scientific studies and perhaps especially in palaeontology, Goethe was at times orthodox and at other times highly heterodox. His fundamental project was to comprehend the unifying principle within all nature and in that respect he was one of the early, great holistic thinkers. Goethe proposed a theory of a dynamic unifying ‘type’ for both plants and animals, working together with an inherent creative drive, which he believed was present in all nature. Here I show how he used this model to interpret the morphologies of extinct Plio-Pleistocene mammals such as the aurochs and giant sloth, and also demonstrate how Goethe's dynamic thinking led to some tentative pre-Darwinian transformationist (‘evolutionary’) propositions.

Nomenclatural history of Megalonyx Jefferson, 1799 (Mammalia, Xenarthra, Pilosa, Megalonychidae).

Both authorship and spelling of the extinct giant sloth genus Megalonyx and its type species, M.jeffersonii (Mammalia, Xenarthra, Pilosa, Megalonychidae), have been inconsistent. The genus-group name has been cited with two different authorships and three dates, and it has been spelled with two different suffixes. The species-group name has been cited with four different authors and dates, and it has been spelled with two different endings. Megalonyx Jefferson, 1799 is the first valid use of the genus-group name; the correct original spelling has the -onyx suffix. The type species of Megalonyx is Megatheriumjeffersonii Desmarest, 1822; the correct original spelling has an -ii ending. A vernacular word, megalonyx, refers to species classified in the genus Megalonyx Jefferson, 1799.

Paleoecological inferences about the Late Quaternary giant sloths

Paleoecological inferences about the Late Quaternary giant sloths

Eiko Kitao: Fossil Hunter and Passionate Educator

From uncovering giant ground sloths to helping build a fossil database, Kitao goes above and beyond as a laboratory technician at Santa Barbara City College.

Histotaphonomy of a Pleistocene megamammal assemblage from Argentine Pampas

This work involves a multy-proxy approach of taphonomic features of the extinct giant ground sloth Lestodon armatus (Xenarthra, Mylodontidae). The study is based on paleohistological, mineralogical, and geochemical analyses from the Late Pleistocene Playa del Barco site (Buenos Aires Province, Argentina). Transverse thin sections of ribs and vertebrae were studied under light microscope, polarizing petrographic microscope, and scanning electron microscope (SEM), combined with chemical analysis using energy dispersive spectroscopy (EDS) and micro-X-ray diffraction (μXRD). The internal crystalline structure and mineral composition remains almost unaltered. The bone microstructure is well preserved in all the samples, although it was affected by different types of microfractures and infillings. Numerous radial microcracks were identified in the secondary osteons of all specimens evidencing wet depositional environment. The mineralogical and geochemical composition of the infillings and encrustations indicates that the enrichment with new elements was due to direct exchange with the sediments in which they were buried. Mineralogical evidence from the infillings allows to identify different diagenetic pathways; most of the skeletal elements were quickly buried in the vadose zone, while others were buried in the phreatic zone, directly or after some time immersed in a continental aquatic context. The fossildiagenetic information obtained from the Lestodon armatus fossils provides novel information to interpret and reconstruct the whole taphonomic history and the environmental and climatic conditions that favored the preservation of the Playa del Barco fossil assemblage during the end of the Last Glacial Maximum.

Evidence of artefacts made of giant sloth bones in central Brazil around the last glacial maximum.

The peopling of the Americas and human interaction with the Pleistocene megafauna in South America remain hotly debated. The Santa Elina rock shelter in Central Brazil shows evidence of successive human settlements from around the last glacial maximum (LGM) to the Early Holocene. Two Pleistocene archaeological layers include rich lithic industry associated with remains of the extinct giant ground sloth Glossotherium phoenesis. The remains include thousands of osteoderms (i.e. dermal bones), three of which were human-modified. In this study, we perform a traceological analysis of these artefacts by optical microscopy, non-destructive scanning electron microscopy, UV/visible photoluminescence and synchrotron-based microtomography. We also describe the spatial association between the giant sloth bone remains and stone tools and provide a Bayesian age model that confirms the timing of this association in two time horizons of the Pleistocene in Santa Elina. The conclusion from our traceological study is that the three giant sloth osteoderms were intentionally modified into artefacts before fossilization of the bones. This provides additional evidence for the contemporaneity of humans and megafauna, and for the human manufacturing of personal artefacts on bone remains of ground sloths, around the LGM in Central Brazil.

Inferences of the ecological habits of extinct giant sloths from the Brazilian Intertropical Region

ABSTRACTThree indices estimated from measurements of the humerus and ulna were used to suggest possible ecological habits of eight extinct giant sloths from the Late Pleistocene of the Brazilian Intertropical Region. To make these inferences, data from extant primates and xenarthras representing suspensory, climbing and digging forms were compared. The results indicate niche differentiation existed between these species; Ahytherium aureum, Australonyx aquae and Nothrotherium maquinense could have been climbers, Catonyx cuvieri, Ocnotherium giganteum and Glossotherium phoenesis were diggers, while Valgipes bucklandi and Eremotherium laurillardi were strictly terrestrial in their habits. These results suggest a general pattern in which members of the Megalonychidae and Nothotheriidae were mainly climbers, whereas mylodontines were mainly diggers, and scelidotheres were strictly terrestrial along with members of the giant Megatheriidae.

The Yale Geochronometric Laboratory and the Rewriting of Global Environmental History.

Beginning in the nineteenth century, scientists speculated that the Pleistocene megafauna-species such as the giant ground sloth, wooly mammoth, and saber-tooth cat-perished because of rapid climate change accompanying the end of the most recent Ice Age. In the 1950s, a small network of ecologists challenged this view in collaboration with archeologists who used the new tool of radiocarbon dating. The Pleistocene overkill hypothesis imagined human hunting, not climate change, to be the primary cause of megafaunal extinction. This article situates the Pleistocene overkill hypothesis in a broader history of the emergence of historical ecology as a distinct sub-discipline of paleoecology. Tracing the work of the Yale Geochronometric Laboratory and an interdisciplinary research network that included Paul Sears, Richard Foster Flint, Edward Deevey, Kathryn Clisby, and Paul S. Martin, it reveals how both the methods and the meaning of studying fossil pollen shifted between the 1910s and 1960s. First used as a tool for fossil fuel extraction, fossil pollen became a means of envisioning climatic history, and ultimately, a means of reimagining global ecological history. First through pollen stratigraphy and then through radiocarbon dating, ecologists reconstructed past biotic communities and rethought the role of humans in these communities. By the 1980s, the discipline of historical ecology would reshape physical environments through the practice of ecological restoration.

The last record of the last typotherid (Notoungulata, Mesotheriidae, Mesotherium cristatum) for the middle Pleistocene of the western Pampean region, Córdoba Province, Argentina, and its biostratigraphic implications

We document a new Last Appearance Datum of the mesotheriine notoungulate Mesotherium cristatum in 220 ± 13 ka, Middle Pleistocene of the west Pampean Region of the Province of Cordoba, Corralito, Santa María Department, Argentina. We increase the previous LAD of this taxon into ca. 530 ka compared to its latest occurrence in Ensenadan Age (ca. 1.95–0.4 Ma; Early-Middle Pleistocene) sediments from the east Pampean Region.Our detailed literature review of the traditional biostratigraphic support (“Mesotherium cristatum Biozone”) of the Ensenadan Age for the east Pampean Region, and our new temporal record of M. cristatum for the western region of the Pampean Region, .allows us to draw the following conclusions that affect the biostratigraphic model considered so far extensive in South America: (1) M. cristatum should no longer be considered as the guide taxon of the Ensenadan Age; (2) “M. cristatum Biozone” no longer constitutes the biostratigraphic support of the Ensenadan Age as it is also present in sediments of Bonaerian Age; (3) Distinct biostratigraphic units (“M. cristatum Biozone” and “Megatherium americanum Biozone”) overlap in their temporal ranges. In application of the International Stratography Code, we proclaim that the models of chronostratigraphic and biostratigraphic units, established for the Pampean Region, need a strong and consolidated biostratigraphic support, whose temporal limits must be defined by the presence of fossils and not by the temporal limits of the chronostratigraphic units.This study proclaims the biostratigraphic importance of the western Pampean Region near the Sierras Pampeanas (Córdoba Province) which due to its differential paleoecological conditions and its altitudinal diferenciation with respect to the eastern regions of the Pampean Region could have acted as a faunal reservoir during the Pleistocene.

Fotogrametria de um icnofóssil escavado por preguiças-gigantes (Megaichnus major)

Photogrammetry of an excavated ichnofossil by giant sloths (Megaichnus major). During the Pliocene and Pleistocene, the extinct giant mammals that lived in South America had the burrowing behavior that, in the search for shelter and refuge, produced large ichnofossils called Megaichnus (paleoburrows). Megaichnus are biogenic structures in the form of tunnels and halls excavated by Folivora (Megaichnus major) and Cingulata (Megaichnus minor). On the ceiling and walls of these paleoburrows, it is possible to observe traces of excavation of these animals. Photogrammetry was performed by imaging M. major to generate the Three-Dimensional Digital Model (3DM). The paleoburrow is located in the Municipality of Doutor Pedrinho (Santa Catarina State) and was excavated in the sandstone of the Taciba Formation (Permian). The photographs were processed to generate the 3DM and the virtual reality interface with 3D glasses. The 3DMs are available for viewing on the Sketchfab website through the links (GoPro 4; https://skfb.ly/6RYyn) and (Nikon D60; https://skfb.ly/ooprJ). 3DM allows easy access to the ichnofossils, making it possible to study them remotely from anywhere in the world. The construction of 3DMs of the paleoburrows, through high-resolution photogrammetry, is an innovative proposal, and allows wide dissemination of knowledge about these structures. Keywords: paleoburrows, Quaternary, megafauna, 3D imaging.

Megafauna kill sites in South America: A critical review

South America is the continent with the largest amount of megafauna extinctions at the end of the Pleistocene (∼50 genera), but the empirical evidence of megafauna exploitation by humans is little known by the international scientific community and often ignored from systematic reviews of global megafauna extinctions. Here, we systematically searched for archaeological records with human-megafauna interaction in South America, and then classified and described the megafauna kill sites (MKSs) by following three protocols with successively restricting criteria: Grayson and Meltzer (2015, 2002), Borrero (2009) and Mothé et al. (2020). We identified 134 studies presenting 69 archaeological sites with evidence of human-megafauna interactions over the late Quaternary of South America (from ∼17,000 cal yr BP to ∼7,900 cal yr BP), from which we classified up to 17 reliable MKSs with 15 exploited megafauna genera. Our results show that humans have exploited mastodons, giant ground sloths, giant armadillos, equids, bears, cervids and camelids for over 10,000 years, a much longer period than predicted by Paul Martin's overkill hypothesis. By synthesizing the complete evidence about human-megafauna interaction in an unnoticed continent, our database (available at www.killsitedatabase.com) fill an important gap from the international literature and will shed light on the analyses about the role of the human hunting activity on late Quaternary extinctions.

A comparative study of the postcranial skeleton of Patagonian and Pampean specimens of the Pleistocene giant sloth genus Mylodon Owen, 1839 (Xenarthra, Pilosa) and its implications

ABSTRACT In this work, we describe postcranial elements of Mylodon listai distributed in collections from Argentina, Chile and Europe. Mylodon listai remains from Patagonia are clearly different from those from the Pampean region (Mylodon darwinii), presenting morphological differences in their postcranium such as a smaller intercondylar space and less displacement of the medial condyle in the femur. These anatomical features reveal that M. listai had less bowed legs than M. darwinii. We propose that this would be an adaptation to a less fossorial lifestyle in their habitats in southern Patagonia without having to do directly with differences in body mass in the southern specimens, because M. listai would have reached similar or even larger sizes than M. darwinii.

A new specimen of Eremotherium laurillardi (Xenarthra, Megatheriidae) from the Late Pleistocene of Chiapas, and comments about the distribution of the species in Mexico

Eremotherium laurillardi was a common giant ground sloth in the Late Pleistocene of the Americas. A right femur referable to this species was recovered from fluvial sediments in Constitución 27 colony, Socoltenango municipality, in the southern State of Chiapas, Mexico. The femur shows the morphological characteristics of E. laurillardi, such as: large size; rectangular shape, it is dorsoventrally flattened; lateral and medial margin rectilinear and parallel, and patellar trochlea transversely elongated with the medial margin in the sagittal plane of the femur. The record from Constitución 27 town, adds a new locality for E. laurillardi in Mexico, which adds to the previously known seven localities with remains of this species in Chiapas. In Mexico, E. laurillardi is present in 31 localities distributed in 13 states, mainly in the central and southern portion of Mexico, with an altitudinal range between 0-200 up to 2000-2500 meters above sea level, indicating a mostly tropical distribution of this species.

Inferring the paleoecology of the Late Pleistocene giant ground sloths from the Brazilian Intertropical Region

This paper provides diet interpretations for nine giant ground sloth species that lived in the Brazilian Intertropical Region, through the relative muzzle width technique and occlusal surface area (except Mylodonopsis ibseni). We propose that Eremotherium laurillardi, Ocnotherium giganteum, Mylodonopsis ibseni, Glossotherium phoenesis, Catonyx cuvieri, Valgipes bucklandi, Ahytherium aureum, and Australonyx aquae were adapted to had a mixed-feeder diet, having a great oral food processing, which could indicate an adaptation to need less from the fermentation on digestive tract, and similar, or even higher, metabolic requirements in comparison with ungulates of similar body mass. While, N. maquinense was adapted to a browser diet, and probably presented high fermetantion capability and low metabolic requirement, in comparison with all other giant ground sloth taxa.

CT Visualization of Vasculature Channels in Modern and Fossil Sloth Ungual Claws

One of the interesting features of modern sloths is the vasculature patterns of their upper and lower limbs. Even though sloths are endothermic like other mammals, their mean body temperature tends to be lower, more variable, and more linked to the ambient temperature than other placental mammals. Like some other mammals from environments with temperature extremes, they possess rete arteriovenous bundles, which work as an effective heat exchange mechanism, where heat from distally flowing arterial blood is transferred to proximally flowing venous blood. This minimizes the heat loss from the extremities while still maintaining blood flow. The temperature gradient increases in the rete system when the animal’s core temperature decreases, which cools the limbs and preserves core body heat. When the body temperature rises the flow through the superficial venous system increases, which promotes heat loss and body cooling.This begs the question of how this complex vasculature system may or may not extend to the distal phalanges and claws of the sloth, perhaps their most distinctive feature. One possibility could be that to work with the limb cooling function of the rete system, the distal phalanx and claw may be poorly vascularized so as not to increase chances for heat loss. However, considering the extensive and important use of their claws, they may require extensive vascularization to withstand the large amount of stress they are often under. This study uses Micro CT scans of sloth ungual phalanges to visualize their vascular channels. In both modern and extinct giant ground sloths, vascular networks through the bone of the ungual phalanx are quite extensive, and are very clearly linked to externally visible channels and impressions left by the proper digital arteries. In ground sloths these internal vascular channels quickly branch on either side and continue distally, letting off smaller branches as they go. These channels are rather large, even appearing to be artificial drill holes on one specimen that has the distal end broken off. Modern sloths show a similar pattern, but their vascular channels take up proportionally less space in the bone than in the giant ground sloths. This difference may be due extinct giant ground sloths’ more varied use of their claws. These complex patterns show that sloth claws require a significant blood supply, and may indicate that the rete system is effective enough that by the time the arterial blood gets to the distal phalanx it has been sufficiently cooled to not be a significant source of heat loss.

Spinal fracture reveals an accident episode in Eremotherium laurillardi shedding light on the formation of a fossil assemblage

The Toca das Onças cave is one of the most important Quaternary mammal deposits of Brazil. Two different hypotheses have been proposed to explain the preservation mode of its skeletal remains: either the animals climbed down into the cave, or it could have functioned as a natural trap. Evaluation of pathological modifications on three articulated vertebrae of a single adult giant ground sloth Eremotherium laurillardi reveals a particular type of bone fracture caused by compressive force on the vertebral column, which split the vertebral bodies in the sagittal plane. This diagnosis suggests that the animal accidentally fell into the cave, in accordance with the second hypothesis proposed to the incorporation mode of skeletal remains into the cave.

Ice Age megafauna rock art in the Colombian Amazon?

Megafauna paintings have accompanied the earliest archaeological contexts across the continents, revealing a fundamental inter-relationship between early humans and megafauna during the global human expansion as unfamiliar landscapes were humanized and identities built into new territories. However, the identification of extinct megafauna from rock art is controversial. Here, we examine potential megafauna depictions in the rock art of Serranía de la Lindosa, Colombian Amazon, that includes a giant sloth, a gomphothere, a camelid, horses and three-toed ungulates with trunks. We argue that they are Ice Age rock art based on the (i) naturalistic appearance and diagnostic morphological features of the animal images, (ii) late Pleistocene archaeological dates from La Lindosa confirming the contemporaneity of humans and megafauna, (iii) recovery of ochre pigments in late Pleistocene archaeological strata, (iv) the presence of most megafauna identified in the region during the late Pleistocene as attested by archaeological and palaeontological records, and (v) widespread depiction of extinct megafauna in rock art across the Americas. Our findings contribute to the emerging picture of considerable geographical and stylistic variation of geometric and figurative rock art from early human occupations across South America. Lastly, we discuss the implications of our findings for understanding the early human history of tropical South America.This article is part of the theme issue ‘Tropical forests in the deep human past’.