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A new material of a Quaternary waterfowl is described here. The implications of this finding, in the context of the dispersal of Anatidae in the past, are discussed. The specimen consists in a partial humerus coming from the Upper Pleistocene of austral Chaco from Santiago del Estero Province, Argentina. The specimen here described belongs to the tribe Cygnini, being larger than most members of the clade. The humerus shows different size than with other members of the tribe Cygnini, being larger than the humeri referred to the Andean goose (Oressochen melanopterus), the Sheldgeese of the genus Chloephaga, the Comb Duck (Sarkidiornis sylvicola), and larger than the Ruddy Shelduck (Tadorna ferruginea). However, the humerus have several anatomical characters indicating that it belongs to a basal anserine duck. These combinations of features allow us to assign this fossil to a species of waterfowl: Coscoroba coscoroba. This finding, it context with the history of the South American Cygnini, provides new environmental interpretations associated with wetlands, which will be tested in the austral Chaco and Northern Pampa through future multi-proxy studies. Keywords: Anseriformes bird, goose, Coscoroba coscoroba, Quaternary, South America, Santiago del Estero.

Felids are the top predators in the environments they inhabit. They entered South America at the Pliocene-Pleistocene boundary, but their fossil record in Uruguay, although informative, is scarce. In the present contribution, three new materials (two hemimandibles and an isolated first lower molar) assigned to Panthera onca (Linnaeus, 1758) are described. This material came from Quaternary sediments (Sopas, Dolores, and Libertad Formations) from several localities in Uruguay. Based on this material, different aspects of the paleobiology and paleoecology of jaguars are discussed. Remains of these felids were previously listed but never described; thus, the material analyzed here is the first fossil records reliably determined for P. onca in Uruguay. These felids would have shared an ecological niche with other large carnivores during the late Pleistocene in Uruguay, such as saber-toothed cats (Smilodon populator Lund, 1842; S. fatalis Leidy, 1868), Puma concolor Linnaeus, 1771, and short face bears Arctotherium Burmeister, 1879; and they would have fed upon medium-sized herbivores, principally in vegetated environments.

Felidae entered South America from North America during the Ensenadan Stage/Age (Early to Middle Pleistocene). For Uruguay their fossil record is scarce but informative, although mostly correspond to large felids (Smilodon, Panthera onca). In this work describes fossil remain of a skull and a mandible assigned, based on morphology and statistical analysis, to Puma concolor. These materials were unearthed from Late Pleistocene sediments (Sopas Formation) from northern Uruguay. Based on these remains some paleobiological and paleoecological aspects are discussed. This specimen had a body mass of about 45 kg, with the potential capacity to hunt animals over 200 kg, which is in agreement with previous reports for other fossil puma remains. During Late Pleistocene, in the current territory of Uruguay, Puma concolor would have shared ecological niche with other large carnivore such as sabre-tooth cats (Smilodon populator, S. fatalis), the jaguar Panthera onca, the canid Protocyon troglodytes, and short-faced bears Arctotherium, feeding upon medium-sized animals in diverse environment.

Among the three recognized species of Smilodon, S. populator is the largest in size and has the widest distribution across South America. The present contribution describes an almost complete skull...

Living elephants produce seismic waves during vocalizations and locomotion that are potentially detectable at large distances. In the Mesozoic world, seismic waves were probably a very relevant source of information about the behavior of large dinosaurs. In this work, we study the relationship between foot shape and the directivity pattern of seismic waves generated during locomotion. For enlarged foot morphologies (based on a morphological index) of theropod dinosaurs, there is a marked effect of seismic wave directivity at 20 m. This effect is not important in the foot morphologies of other dinosaurs, including the foot shapes of herbivores and theropods such as therizinosaurids. This directivity produces a lower intensity in the forward direction that would slightly reduce the probability of detection of an ambush predator. Even more relevant is the fact that during the approach of a predator, the intensity of seismic waves detected by potential prey remains constant in the mentioned distance range. This effect hides the predator's approach, and we call this “seismic wave camouflage”. We also discuss the potential relationship of this effect with enlarged fossil footprints assigned to metatarsal support.

We report new fossil evidence of terror bird survival until the end of the Pleistocene in Uruguay. The new specimens comprise the distal portion of right tarsometatarsus and a left humerus; the latter is assigned to the genus Psilopterus. The sedimentary context of the remains yields a characteristic Pleistocene mammalian association along with numerical age dating giving an undoubted late Pleistocene age (OSL 96,040 ± 6300 years). We also revise and discuss the systematic placement of late Pleistocene phorusrhacid material previously published. The trophic role of terror birds and other South American carnivorous birds in late Pleistocene ecosystems should be revised based on the increasing findings of avian fossil materials.

An exceptionally well-preserved skull of the Pliocene rodent Telicomys giganteus allowed the first estimation of body mass and analysis of the bite mechanics of this species of South American giant rodent. In this study, we reconstructed the main anatomical features of the skull of this Pliocene rodent and related them to the bite force at the incisors. The average of an estimation body mass gives 100 kg. We also estimated the bite force using three different techniques. Two methods suggest that bite forces at the incisors have a range of 500–1000 N. However, the incisors seem to be stronger than expected for this bite force, implying that the bite forces may have been greater than 2000 N. We consider the hypothesis of defense against predators or other agonistic behavior to explain our results.

Mesosaurid biology has been subject of continuous debate since the first description of Mesosaurus tenuidens by Paul Gervais in 1867. Controversy surrounds their environmental and feeding preferenc...

The Miocene Santacrucian sloths are a very important assemblage because they represent the first major radiation among sloths and, therefore, they could provide many insights about sloth evolution and diversity. Based on other studies, the hearing capabilities of Pleistocene sloths were identified. For a deeper understanding of these capabilities from an evolutionary point of view, in this article we study the hearing capabilities of Santacrucian sloths. We estimate the frequency range and the best frequency of hearing of six species of stem-megatherines and one species of mylodont. In most cases, the best frequency of hearing is much lower than the expected value for the estimated body mass of the species. This general shift towards low values of frequency is different than the pattern observed in mammals where sound localisation is improved by an increased sensitivity to high frequencies. In this article, we also propose some palaeobiological inferences of the low-frequency shift of hearing range in Mio...

Although the growth and development of tissues and organs of extinct species cannot be directly observed, their fossils can record and preserve evidence of these mechanisms. It is generally accepted that bone architecture is the result of genetically based biomechanical constraints, but what about osteoderms? In this article, the influence of physical constraints on cranial osteoderms growth is assessed. Comparisons among lepidosaurs, synapsids, and archosaurs are performed; according to these analyses, lepidosaur osteoderms growth is predicted to be less energy demanding than that of synapsids and archosaurs. Obtained results also show that, from an energetic viewpoint, ankylosaurid osteoderms growth resembles more that of mammals than the one of reptilians, adding evidence to debate whether dinosaurs were hot or cold blooded. J. Morphol. 275:923–932, 2014. © 2014 Wiley Periodicals, Inc.

The unusual mix of morphological traits displayed by extinct South American native ungulates (SANUs) confounded both Charles Darwin, who first discovered them, and Richard Owen, who tried to resolve their relationships. Here we report an almost complete mitochondrial genome for the litoptern Macrauchenia. Our dated phylogenetic tree places Macrauchenia as sister to Perissodactyla, but close to the radiation of major lineages within Laurasiatheria. This position is consistent with a divergence estimate of ∼66 Ma (95% credibility interval, 56.64–77.83 Ma) obtained for the split between Macrauchenia and other Panperissodactyla. Combined with their morphological distinctiveness, this evidence supports the positioning of Litopterna (possibly in company with other SANU groups) as a separate order within Laurasiatheria. We also show that, when using strict criteria, extinct taxa marked by deep divergence times and a lack of close living relatives may still be amenable to palaeogenomic analysis through iterative mapping against more distant relatives., Classification of the extinct South American native ungulates (SANUs) has posed a challenge given the absence of close, surviving relatives. Here, Westbury et al. sequence the mitochondrial genome of the extinct SANU Macrauchenia patachonica and reconstruct the evolutionary history of the lineage.

The caracaras belong to a group of falconids with widespread geographical distribution in the Western Hemisphere, particularly in South America. Here we report fossil remains of a new species attributed to the genusCaracarafrom the late Pleistocene of Uruguay. This bird would have had an estimated body mass of 3700 grams, a value that greatly exceeds the maximum body mass reported for living falconids. Apparently, it would have had flying capabilities, in contrast to another paleospecies recently described from the Holocene of Jamaica. This fossil bird was found in association with mammal megafaunal remains and could offer new insights about the role of carnivorous birds in late Pleistocene environments of South America.

We report the youngest record of a phorusrhacid bird based on a distal portion of a right tarsometatarsus. This fossil comes from late Pleistocene sediments of Uruguay. The age determination was based on lithological features, biostratigraphical studies and absolute dating. The evidence indicates that these groundbirds co-occurred with the typical Pleistocene South American megafaunal mammals. The so far youngest fossils of phorusrhacids stem from the Pliocene or lower Pleistocene of South and North America.

‘Terror bird’ is a common name for the family Phorusrhacidae. These large terrestrial birds were probably the dominant carnivores on the South American continent from the Middle Palaeocene to the Pliocene–Pleistocene limit. Here we use a mechanical model based on tibiotarsal strength to estimate maximum running speeds of three species of terror birds:Mesembriornis milneedwardsi,Patagornis marshiand a specimen of Phorusrhacinae gen. The model is proved on three living large terrestrial bird species. On the basis of the tibiotarsal strength we propose thatMesembriorniscould have used its legs to break long bones and access their marrow.

The genus Neoglyptatelus Carlini, Vizcaíno and Scillato-Yané has been considered a member of Glyptatelinae, a group encompassing the purportedly basal-most glyptodonts. It is up to now represented by two species from Colombia: Neoglyptatelus originalis Carlini, Vizcaíno and Scillato-Yané, from the middle Miocene (a carapace fragment, isolated osteoderms and postcranial bones), and Neoglyptatelus sincelejanus Villarroel and Clavijo, from the middle or late Miocene (a partial carapace and a caudal armor). More scarce material assigned to this genus was recovered from the late Miocene of Uruguay and Brazil. In this article, we describe a new species, Neoglyptatelus uruguayensis, from the late Miocene Camacho Formation, Uruguay, based on an almost complete carapace and several postcranial bones. We conducted a phylogenetic analysis based on 167 morphological characters (23 new ones and 144 from previous analysis) scored for 19 taxa, encompassing some of the best known glyptodontid genera, one pampathere and four armadillos (including the enigmatic genus Pachyarmatherium Downing and White). In the most parsimonious tree that was obtained, Neoglyptatelus forms a clade with Pachyarmatherium (Pachyarmatheriidae), which is the sister group of the glyptodonts + pampatheres clade; consequently, it is not a glyptodont, as previously believed. This result, together with the known stratigraphic and geographic distribution of Neoglyptatelus and Pachyarmatherium, suggests that this new cingulate clade originated in South America and that Pachyarmatherium reached North America during the Plio--Pleistocene. The carapace of Neoglyptatelus and Pachyarmatherium comprises pelvic and scapular shields overlapping each other without separate intervening transverse mobile bands, an arrangement that differentiates both genera from the remaining cingulates. Fil: Fernicola, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Universidad Nacional de Luján; Argentina Fil: Rinderknecht, Andrés. Museo Nacional de Historia Natural; Uruguay Fil: Jones, Washington. Museo Nacional de Historia Natural; Uruguay Fil: Vizcaíno, Sergio Fabián. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina Fil: Porpino, Kleberson de Oliveira. Universidade Do Estado Do Rio Grande Do Norte; Brasil

Arctotherium angustidens Gervais and Ameghino, 1880 (the South American giant short-faced bear) is known for being the earliest (Ensenadan Age, early to middle Pleistocene) and largest (body mass over 1 ton) of five described Arctotherium species endemic to South America. Here we assess the diet of this bear from multiple proxies: morphology, biomechanics, dental pathology, stable isotopes and a previous study using geometric morphometric methodology. Results favor the idea of animal matter consumption, probably from large vertebrates in addition to vegetable matter consumption. Most probably, active hunting was not the unique strategy of this bear for feeding, since its large size and great power may have allowed him to fight for the prey hunted by other Pleistocene carnivores. However, scavenging over mega mammal carcasses was probably another frequent way of feeding. South American short-faced bears adjusted their size and modified their diet through Pleistocene times, probably as a response to the diversification of the carnivore guild (from the few precursory taxa that crossed the Panamanian Isthmus during the Great American Biotic Interchange). Fil: Soibelzon, Leopoldo Héctor. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Grispan, Gustavo A.. Universidad de la República; Uruguay Fil: Bocherens, Hervé. University Tübingen; Alemania Fil: Acosta, Walter Gustavo. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina Fil: Jones, Washington. Universidad de la República; Uruguay Fil: Blanco, Ernesto R.. Universidad de la República. Facultad de Ciencias; Uruguay Fil: Prevosti, Francisco Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

Although the growth and development of tissues and organs of extinct species cannot be directly observed, their fossils can record and preserve evidence of these mechanisms. It is generally accepted that bone architecture is the result of genetically based biomechanical constraints, but what about osteoderms? In this article, the influence of physical constraints on cranial osteoderms growth is assessed. Comparisons among lepidosaurs, synapsids, and archosaurs are performed; according to these analyses, lepidosaur osteoderms growth is predicted to be less energy demanding than that of synapsids and archosaurs. Obtained results also show that, from an energetic viewpoint, ankylosaurid osteoderms growth resembles more that of mammals than the one of reptilians, adding evidence to debate whether dinosaurs were hot or cold blooded.

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