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Overkill of large mammals is recognized as a key driver of Pleistocene megafaunal extinctions in the Americas and Australia. While this phenomenon primarily affected mega-mammals, its impact on large Quaternary reptiles has been debated. Freshwater turtles, due to the scarcity of giant forms in the Quaternary record, have been largely neglected in such discussions. Here we present a new giant podocnemidid turtle, Peltocephalus maturin sp. nov., from the Late Pleistocene Rio Madeira Formation in the Brazilian Amazon, that challenges this assumption. Morphological and phylogenetic analyses of the holotype, a massive partial lower jaw, reveal close affinities to extant Amazonian species and suggest an omnivorous diet. Body size regressions indicate Pe. maturin possibly reached about 180 cm in carapace length and is among the largest freshwater turtles ever found. This finding presents the latest known occurrence of giant freshwater turtles, hinting at coexistence with early human inhabitants in the Amazon.

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Tardigrades are a diverse group of charismatic microscopic invertebrates that are best known for their ability to survive extreme conditions. Despite their long evolutionary history and global distribution in both aquatic and terrestrial environments, the tardigrade fossil record is exceedingly sparse. Molecular clocks estimate that tardigrades diverged from other panarthropod lineages before the Cambrian, but only two definitive crown-group representatives have been described to date, both from Cretaceous fossil deposits in North America. Here, we report a third fossil tardigrade from Miocene age Dominican amber. Paradoryphoribius chronocaribbeus gen. et sp. nov. is the first unambiguous fossil representative of the diverse superfamily Isohypsibioidea, as well as the first tardigrade fossil described from the Cenozoic. We propose that the patchy tardigrade fossil record can be explained by the preferential preservation of these microinvertebrates as amber inclusions, coupled with the scarcity of fossiliferous amber deposits before the Cretaceous.

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The phylogenetic paradigm of eukaryotic evolution has changed dramatically over the past two decades, with profound reflections on the understanding of life on earth. Arcellinida testate (shelled) amoebae lineages represent some of the oldest fossils of eukaryotes, and the elucidation of their phylogenetic relationships opened a window to the distant past, with important implications for understanding the evolution of life on earth. This four-part essay summarises advances made in the past 20 years regarding: (i) the phylogenetic relationships among amoebae with shells evolving in concert with the advances made in the phylogeny of eukaryotes; (ii) paleobiological studies unraveling the biological affinities of Neoproterozoic vase-shaped microfossils (VSMs); (iii) the interwoven interpretation of these different sets of data concluding that the Neoproterozoic contains a surprising diversity of organisms, in turn demanding a reinterpretation of the most profound events we know in the history of eukaryotes, and; (iv) a synthesis of the current knowledge about the evolution of Arcellinida, together with the possibilities and pitfalls of their interpretation.

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Notoungulates were a diverse group of South American ungulates that included the rodent-like typotherians. However, they are typically compared with other ungulates and interpreted as grazers. Here we present the first detailed reconstruction of the masticatory muscles of the pachyrukhine typotherians Paedotherium and Tremacyllus. An outstanding feature is the presence of a true sciuromorph condition, defined by an anterior portion of the deep masseter muscle originating from a wide zygomatic plate that reaches the rostrum, a trait traceable since the Oligocene pachyrukhines. Consequently, pachyrukhines are the first case of sciuromorph non-rodent mammals. This morphology would have allowed them to explore ecological niches unavailable for the exclusively hystricomorph coexisting rodents. This innovative acquisition seems to be synchronous in Pachyrukhinae and sciuromorph rodents and related to hard-food consumption. We postulate the expansion of nut and cone trees during the major environmental changes at Eocene-Oligocene transition as a potential trigger for this convergence.

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Widespread fish clades that occur mainly or exclusively in fresh water represent a key target of biogeographical investigation due to limited potential for crossing marine barriers. Timescales for the origin and diversification of these groups are crucial tests of vicariant scenarios in which continental break-ups shaped modern geographic distributions. Evolutionary chronologies are commonly estimated through node-based palaeontological calibration of molecular phylogenies, but this approach ignores most of the temporal information encoded in the known fossil record of a given taxon. Here, we review the fossil record of freshwater fish clades with a distribution encompassing disjunct landmasses in the southern hemisphere. Palaeontologically derived temporal and geographic data were used to infer the plausible biogeographic processes that shaped the distribution of these clades. For seven extant clades with a relatively well-known fossil record, we used the stratigraphic distribution of their fossils to estimate confidence intervals on their times of origin. To do this, we employed a Bayesian framework that considers non-uniform preservation potential of freshwater fish fossils through time, as well as uncertainty in the absolute age of fossil horizons. We provide the following estimates for the origin times of these clades: Lepidosireniformes [125-95 million years ago (Ma)]; total-group Osteoglossomorpha (207-167 Ma); Characiformes (120-95 Ma; a younger estimate of 97-75 Ma when controversial Cenomanian fossils are excluded); Galaxiidae (235-21 Ma); Cyprinodontiformes (80-67 Ma); Channidae (79-43 Ma); Percichthyidae (127-69 Ma). These dates are mostly congruent with published molecular timetree estimates, despite the use of semi-independent data. Our reassessment of the biogeographic history of southern hemisphere freshwater fishes shows that long-distance dispersals and regional extinctions can confound and erode pre-existing vicariance-driven patterns. It is probable that disjunct distributions in many extant groups result from complex biogeographic processes that took place during the Late Cretaceous and Cenozoic. Although long-distance dispersals likely shaped the distributions of several freshwater fish clades, their exact mechanisms and their impact on broader macroevolutionary and ecological dynamics are still unclear and require further investigation.

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Fossil remains provide useful insights into the long-term impact of anthropogenic phenomena on faunas and are often used to reveal the local (extirpations) or global (extinctions) losses of populations or species. However, other phenomena such as minor morphological changes can remain inconspicuous in the fossil record depending on the methodology used. In this study, we used the anole of Marie-Galante Island (Anolis ferreus) in Guadeloupe (French, West Indies) as a model to demonstrate how the morphological evolution of an insular lizard can be tracked through the Pleistocene/Holocene climatic transition and the recent anthropization of the island. We used a fossil assemblage of nearly 30 000 remains and a combination of anatomical description, traditional morphometry and geometric morphometrics. These fossils are attributed to a single taxon, most likely to be A. ferreus on the basis of morphological and morphometric arguments. Our results show the disappearance of a distinct (sub)population of large specimens that were about 25% larger than the modern representatives of A. ferreus We also demonstrate an apparent size stability of the main fossil population of this species since the Late Pleistocene but with the possible occurrence of a reduction in morphological diversity during the Late Holocene. These results highlight the impact of anthropic disturbances on a lizard whose morphology otherwise remained stable since the Late Pleistocene.

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Ancient DNA of extinct species from the Pleistocene and Holocene has provided valuable evolutionary insights. However, these are largely restricted to mammals and high latitudes because DNA preservation in warm climates is typically poor. In the tropics and subtropics, non-avian reptiles constitute a significant part of the fauna and little is known about the genetics of the many extinct reptiles from tropical islands. We have reconstructed the near-complete mitochondrial genome of an extinct giant tortoise from the Bahamas (Chelonoidis alburyorum) using an approximately 1 000-year-old humerus from a water-filled sinkhole (blue hole) on Great Abaco Island. Phylogenetic and molecular clock analyses place this extinct species as closely related to Galápagos (C. niger complex) and Chaco tortoises (C. chilensis), and provide evidence for repeated overseas dispersal in this tortoise group. The ancestors of extant Chelonoidis species arrived in South America from Africa only after the opening of the Atlantic Ocean and dispersed from there to the Caribbean and the Galápagos Islands. Our results also suggest that the anoxic, thermally buffered environment of blue holes may enhance DNA preservation, and thus are opening a window for better understanding evolution and population history of extinct tropical species, which would likely still exist without human impact.

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The Tremarctinae are a subfamily of bears endemic to the New World, including two of the largest terrestrial mammalian carnivores that have ever lived: the giant, short-faced bears Arctodus simus from North America and Arctotherium angustidens from South America (greater than or equal to 1000 kg). Arctotherium angustidens became extinct during the Early Pleistocene, whereas Arctodus simus went extinct at the very end of the Pleistocene. The only living tremarctine is the spectacled bear (Tremarctos ornatus), a largely herbivorous bear that is today only found in South America. The relationships among the spectacled bears (Tremarctos), South American short-faced bears (Arctotherium) and North American short-faced bears (Arctodus) remain uncertain. In this study, we sequenced a mitochondrial genome from an Arctotherium femur preserved in a Chilean cave. Our molecular phylogenetic analyses revealed that the South American short-faced bears were more closely related to the extant South American spectacled bear than to the North American short-faced bears. This result suggests striking convergent evolution of giant forms in the two groups of short-faced bears (Arctodus and Arctotherium), potentially as an adaptation to dominate competition for megafaunal carcasses.

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Understanding the dialogue between museums and their visitors enables museums to subsist, undergo transformations and become consolidated as socially valued cultural venues. The Museo de La Plata (Argentina) was created in the late nineteenth century as a natural history museum, and this study shows that currently the museum is valued socially as a venue for family leisure and education, at which people make sense to the objects exhibited through characteristics conferred upon them by both the institution and the visitor. Nevertheless, such dialogue is somehow affected by the museographic proposal and the public interpretation of the institutional narrative, which could be analysed within the frame of contextual learning. As a consequence, the evolutionary idea that the museum aims to communicate is distorted by the public. This article highlights the importance of considering the visitors' interpretations when planning museum exhibitions, a perspective that has been rather absent in the Argentinian museums.

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Divergence dating studies, which combine temporal data from the fossil record with branch length data from molecular phylogenetic trees, represent a rapidly expanding approach to understanding the history of life. National Evolutionary Synthesis Center hosted the first Fossil Calibrations Working Group (3–6 March, 2011, Durham, NC, USA), bringing together palaeontologists, molecular evolutionists and bioinformatics experts to present perspectives from disciplines that generate, model and use fossil calibration data. Presentations and discussions focused on channels for interdisciplinary collaboration, best practices for justifying, reporting and using fossil calibrations and roadblocks to synthesis of palaeontological and molecular data. Bioinformatics solutions were proposed, with the primary objective being a new database for vetted fossil calibrations with linkages to existing resources, targeted for a 2012 launch.

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In spite of the fact that South America was an insular continent for most of the Tertiary, it has the highest species diversity for many organismal groups, including bats. However, the colonization of South America by bats has been poorly studied, even though they are the second most speciose order of mammals. A review of taxonomy, systematics, distribution, and the fossil record suggest that there were several dispersals to South America within 3 superfamilies of bats (Emballonuroidea, Noctilionoidea, and Vespertilionoidea). The reconstruction of ancestral areas based on a phylogeny of bats infers that Africa is the geographic area of origin for most basal nodes. This implies that the diversification of Neotropical species in Noctilionoidea occurred after a single colonization of South America from Africa in the Eocene by an ancestor of the New World families Furipteridae, Mormoopidae, Noctilionidae, Phyllostomidae, and Thyropteridae. Within Emballonuroidea, a similar trans-Atlantic dispersal in the Oligocene gave rise to the New World tribe Diclidurini in the family Emballonuridae. The situation for Vespertilionoidea is more complex with multiple dispersals in 3 families (Molossidae, Natalidae, and Vespertilionidae). For Molossidae, there are hypothesized 5 dispersals to South America from Africa beginning in the Eocene but the exact timing and origin of these colonizations a

RESUMO

In spite of the fact that South America was an insular continent for most of the Tertiary, it has the highest species diversity for many organismal groups, including bats. However, the colonization of South America by bats has been poorly studied, even though they are the second most speciose order of mammals. A review of taxonomy, systematics, distribution, and the fossil record suggest that there were several dispersals to South America within 3 superfamilies of bats (Emballonuroidea, Noctilionoidea, and Vespertilionoidea). The reconstruction of ancestral areas based on a phylogeny of bats infers that Africa is the geographic area of origin for most basal nodes. This implies that the diversification of Neotropical species in Noctilionoidea occurred after a single colonization of South America from Africa in the Eocene by an ancestor of the New World families Furipteridae, Mormoopidae, Noctilionidae, Phyllostomidae, and Thyropteridae. Within Emballonuroidea, a similar trans-Atlantic dispersal in the Oligocene gave rise to the New World tribe Diclidurini in the family Emballonuridae. The situation for Vespertilionoidea is more complex with multiple dispersals in 3 families (Molossidae, Natalidae, and Vespertilionidae). For Molossidae, there are hypothesized 5 dispersals to South America from Africa beginning in the Eocene but the exact timing and origin of these colonizations a