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Macrauchenia patachonica Owen, 1838 was among the last and largest litopterns, an extinct order of South American native ungulates. Macrauchenia patachonica had anatomical peculiarities as extremely retracted nasals, enlarged cervical vertebrae, and limb bones proportions without good living analogs that lead to asking about its paleobiology. To quantitatively assess the strange combination of limb bone features in M. patachonica, we constructed an indicator of differences in anatomical adaptations for efficient running between forelimb and hind limb (IDFH). We also made a multivariate analysis using data on osteological ratios of living mammals and two other litopterns. We discuss several biomechanical and paleobiological implications of the striking differences between hind limb and forelimb design in M. patachonica. Our main suggestion is that M. patachonica, during fast locomotion, probably used a posture with the neck in a horizontal position.

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.

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...

Canids are a very diverse and widely distributed group of carnivorous mammals. These animals entered South America in the early stages of faunistic interchange and later during the Pleistocene. However, the fossil record of these organisms is quite scarce on the continent, particularly in Uruguay. In the present contribution, two skulls associated with mandibles are described. Both materials were referred to as individuals of the Pampas fox Lycalopex gymnocercus, which was supported by morphological and morphometric analysis. These materials were found in late Pleistocene sediments (Sopas Formation) from different localities of northern Uruguay. Some aspects of their systematic and trophic dynamics are discussed. The remains of these animals have previously been listed but never described; thus, this material is the first fossil record reliably determined for this species in Uruguay.

The Felidae are known in South America from the Ensenadan Stage/Age onwards. Among them, machairodonts of the genus Smilodon stand out. Three species are recognized, and all three are present on the continent: S. gracilis from the early-middle Pleistocene in north-east Venezuela; S. fatalis, found only in Lujanian sediments on the west side of the Andes (north-west of Peru and south-west of Ecuador); and S. populator, which inhabited the eastern part of the Andes during the Ensenadan and Lujanian. This distribution has led to the suggestion that the last two felids were allopatric during the Lujanian. Here, we report the first evidence of S. fatalis in the eastern part of the continent (Sopas Formation, late Pleistocene of Uruguay), based on an almost complete skull. This finding not only enlarges its distribution in South America but questions the idea of allopatric distribution. It also adds a new component to the mammalian predator trophic level of Uruguay, with the capacity to predate large South American herbivores and megaherbivores. A revision of materials previously assigned to S. populator in the extra-Andean zone of South America will be required.

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.

The fossil record of carnivorous mammals in Uruguay is scarce and fragmentary, but informative. In the present contribution, two new records of canids allocated in sediments of the Dolores Formation (late Pleistocene-early Holocene) are described. These records, based on their anatomical-comparative study and multivariate analysis, correspond to two foxes: one of medium size, Cerdocyon thous, conforms to the first record of this taxon in the country, meanwhile the other one, of larger size, is referred to Dusicyon avus and is the first fossil record of this animal in the south of the territory and the second record in the whole country. Until now, the only carnivorous mammals registered in this formation were the hunters of large herbivores (Arctotherium sp. and Smilodon populator). In this way, these discoveries complement and expand the set of placental mammals with a carnivorous diet for this unit, particularly with the capacity to predate over small- and medium-size mammals.

Procyonids were the first carnivorans that arrived from North America to South America during the late Miocene, before the full emergence of the Panama Isthmus. In South America, this family comprises five living genera (Bassaricyon, Nasua, Nasuella, Potos and Procyon) and two extinct genera (Cyonasua and Chapalmalania) that are recorded from the late Miocene to early Pleistocene. In this contribution, we report and describe specimen MNHN 2965 assigned to Cyonasua sp., which represents the first record of Procyonidae from Uruguay. This specimen was collected at the coastal cliffs of Río de La Plata on the San José Department, in stratigraphic levels that belong to the Camacho Formation (late Miocene). In addition, the presence of Cyonasua sp. in Camacho Fm. is in agreement with the substrate use and locomotor mode inferred for the genus (terrestrial and generalized, with some degree of climbing habits), and with what is known about the paleoenvironment of other formations were Cyonasua was found. Fil: Soibelzon, Leopoldo Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina Fil: Rinderknecht, Andrés. Museo Nacional de Historia Natural; Uruguay Fil: Tarquini, Juliana. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentina Fil: Ugalde, Raúl. Universidad Mayor; Chile. Universidad de la República; Uruguay

In this contribution we report a fossil avian egg with an exceptional preservation. This material was recovered from sediments assigned to the Late Pleistocene-Early Holocene of Uruguay and it could be included as one of the few Cenozoic cases of complete preservation of fossil avian eggs. The micro and macrostructural analysis of the egg and its eggshell allow us to assign it to Family Tinamidae.

We report the first avian bone collected in the Late Pleistocene Dolores Formation, which crops out near Colonia city. The fossil was identified as a femur belonging to an Anatidae that represents the second Anseriform from Uruguay. Two bioerosive traces found on this fossil consist of borings of different sizes and depths were probably occasioned by larvae insect. These traces might have been produced during a brief period of subaerial exposure, in a continental paleoenvironment with dry episodes.

The fossil record of South American cathartids, with few exceptions, is largely restricted to Late Pleistocene and Holocene sites. This contribution provides for the first time fossil records of cathartids from Uruguay. The specimens reported here include an; almost complete fibula, an incomplete furcula, and the distal end of a tibiotarsus. The; first two specimens came from Late Pleistocene beds at two localities of from Northern Uruguay, and the last one comes from Late Pleistocene-Early Holocene beds from South-western Uruguay. All the specimens were associated with several megafaunal fossil remains. The systematic assignation and paleobiological implications of these scavenger birds are here discussed.

South American giant fossil rodents represent a notable example of an extreme evolutionary trend towards size differentiation among caviomorph lineages. Although spectacular, fossil remains of these animals are uncommon and usually highly incomplete. We here describe fully grown adult and juvenile fossil specimens from the rodent family Dinomyidae Alston, 1876, collected from the same location, lithostratigraphical formation and fossiliferous horizon: the coast of the Rio de la Plata of southern Uruguay in pelitic sediments assigned to the late Miocene Camacho Formation. The adult remains consist of an almost complete skull with partial jaw and represent the first published description of associated craneo-mandibular remains of a giant rodent within the subfamily Eumegamyinae. The juvenile specimen is the first to be recognized as such for the entire subfamily, and consists of a complete mandible and a right calcaneus. Based on the homologies observed in the configuration of the teeth, the new specimens a...

Fossiliferous Quaternary sedimentary beds in the Santa Lucia Basin (southern Uruguay) are potentially useful for the study of the last occurrences of extinct taxa, as well as the environmental and climatic patterns in the late Pleistocene to the early Holocene. They have provided a chronological framework (AMS 14C and Optically Stimulated Luminescence dates), a mammalian diversity and interpretations of last occurrence, the climatic-environmental setting, and some associated biogeographic processes. The ages produced encompass the last 30 to 7 ka interval (latest Pleistocene-early Holocene). The mammalian assemblage (36 genera, 24 species) includes typical South American late Pleistocene mammals, extinct species of extant genera, and some extant species that still exist elsewhere on the continent. The preservation pattern includes articulated and semi-articulated skeletons of large and small mammals. The presence in the southern Uruguayan Pampean area of some mammals currently inhabiting Patagonia, northwest and central Argentina (Dolichotis, Galea, Microcavia, Chaetophractus, Lagostomus, and Vicugna) is explained by the predominance of open areas and cold climates associated with the Last Glacial Maximum. The mammalian record depicts local extinctions or shifting ranges occurring in latest Pleistocene or early Holocene. The sedimentary chronological framework and taphonomic features suggest the persistence into the early Holocene of Eutatus seguini, Morenelaphus brachyceros, Equus neogeus, Hemiauchenia sp., Lama sp., and Vicugna sp. Glyptodon and Glossotherium seem to persist at least to the latest Pleistocene. This pattern can substantiate the hypothesis that some megafauna and large mammals persisted for some millennia alongside people with extinction occurring before, during, and after human colonization.

Ubilla, M. & Rinderknecht, A., April 2016. Lagostomus maximus (Desmarest) (Rodentia, Chinchillidae), the extant plains vizcacha in the Late Pleistocene of Uruguay. Alcheringa 40, xxx–xxx. ISSN 0311-5518The extant plains vizcacha, Lagostomus maximus, is described from the Late Pleistocene (Dolores Formation) of Uruguay based on an almost complete articulated skeleton. It is compared with the nominally extinct Pleistocene species of the genus. An AMS 14C taxon-age is determined for L. maximus at 11 879 ± 95 years BP (cal. BP 13 898–13 941). Lagostomus maximus is absent from modern mammal communities in Uruguay, and no Holocene evidence is available. Because L. maximus exhibits remarkable sexual and ontogenetic dimorphism, we examined a range of juvenile, sub-adult and adult male and female specimens. It is not possible to differentiate the articulated Pleistocene fossil from sub-adult specimens of L. maximus based on this sample. Moreover, the skull characteristics, including a broad vertical ramus of the z...

The first record for Uruguay of the dinomyid rodent Tetrastylus Ameghino, an almost complete right mandible from the upper Miocene Camacho Formation, is described. According to the p4 and m3 morphology it is inferred a juvenile-subadult ontogenetic stage for this specimen

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 fossil record of the genus Didelphis, despite its current diversity (6 species, 5 occurring in South America) and wide distribution (from southern Canada to Patagonia, Argentina), is very scarce. The oldest record of the genus in South America comes from Late Miocene sediments and the youngest records from the Late Holocene and historical times. In Uruguay, the only record is stratigraphically questionable because the material has been lost. The present contribution describes the first materials with a precise stratigraphic context assigned to Didelphis cf. D. albiventris, based on comparative morphological and numerical analysis. The materials were unearthed from several outcrops of the Sopas Formation (Late Pleistocene, northern Uruguay) and consist of an associated skull and mandible, right hemimandible, and postcranial material. These findings allow us to discuss several aspects related to the biology and ecology of Didelphis. These animals, which exhibit a mixed diet, were able to feed at intermediate levels of the food chain in highly diverse environments during the Late Pleistocene.

The family Caviidae is a diverse group of South American caviomorph rodents with many living and extinct taxa. Paleontological information about the caviid genus Galea is scant; only two extinct species have been described from fragmentary material so far. Recently, complete skulls and mandibles of the extinct Galea ortodonta have been found (Dolores Fm., Late Pleistocene; Santa Lucia river basin, southern Uruguay). Based on anatomical and quantitative analyses, we provide an expanded diagnosis and description of G. ortodonta, which thus becomes the best-known extinct species of the genus, accompanied by a critical assessment of skull, mandible and dental characters at the generic level. The wide intra-specific variability observed in several characters makes difficult to identify exclusive characters at the species level and to describe species based on fragmentary materials or on mandibles alone. G. ortodonta is characterized by the following associated features: large size; orthodont upper incisor; latero-external face of the incisors with extended enamel; small and laterally compressed auditory bullae; wide basioccipital; maxillary zygomatic process with apophysis; upper cheek teeth with external primary and secondary folds; palatine wide at the mesopterygoid fossa; and horizontal mandibular crest starting at p4. This character association differs from all other living and extinct species of the genus but resembles the G. musteloides species group to some extent. Biostratigraphic information and absolute ages support a Late Pleistocene age for the new material and a correlation with the late phases of Marine Isotope Stage MIS3. Galea occupied lowland areas in southern Uruguay during the Late Pleistocene and, like other associated mammals, suggests open or semi-open areas with an arid or semi-arid context, an environmental scenario arguably influenced by the late phases of MIS3.

A fossil humerus coming from the Rocha Department coasts (Uruguay) is assigned here to Spheniscus cf. S. magellanicus (Aves, Sphenisciformes). This finding, located within the current migratory route of the species, potentially constitutes the northernmost fossil record of S. magellanicus, and the first report of a fossil penguin from Uruguay. Briefly comments about the features supporting its systematic, ontogenetic, and taphonomic assignment are also given.

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.

Recently discovered stapes of Pleistocene South American ground sloths of the genera Lestodon and Glossotherium are studied. Available body mass estimates are larger for Lestodon (4100 kg) than for Glossotherium (1500 kg), reflecting the obvious difference in the overall size of the skull and other bones. However, as previously reported, the absolute size of incus and malleus is very similar in both genera. In a previous work, the frequency range of Glossotherium (from 44 Hz to 15,489 Hz) was estimated quantitatively from well-preserved tympanic ring dimensions. For the first time the frequency ranges of hearing in both genera are estimated by a method based on the footplate area of the stapes. The obtained frequency ranges are consistent with the previous estimation for Glossotherium and are similar in both genera, giving evidence of a frequency range of hearing independent of body size in this group of mammals. Some possible paleobiological implications of the results may include adaptation to some specific sound source, fossoriality, or long-range communication.

Blanco R.E., Rinderknecht, A. & Lecuona, G. 2011: The bite force of the largest fossil rodent (Hystricognathi, Caviomorpha, Dinomyidae). Lethaia, Vol. 45, pp. 157–163. An exceptionally well-preserved skull of the largest fossil rodent Josephoartigasia monesi allows the first analysis of the bite mechanics of this group of South American giant rodents. In this study, we reconstructed the main anatomical features of the skull of this Pliocene rodent, relating them to the bite force at incisors. Bite force was estimated using three different techniques. Two methods suggest that bite forces at incisors of around 1000 N were possible for these mammals. However, the incisors seem to be stronger than expected for this bite force implying that the bite forces may have been greater than 3000 N. We consider three hypotheses: allometric effects, teeth digging or defence against predators, to explain our results. □Bite force, Dinomyidae, incisors, largest rodent, Pliocene.

In this contribution we describe the fossil remains of a new genus and species of a giant rodent, Arazamys castiglionii (Mammalia, Rodentia, Dinomyidae), from Arazati beach in San Jose Department, southern Uruguay. The specimen was exhumed from pelitic sediments of the Camacho Formation, biostratigraphically assigned to the late Miocene Huayquerian South American Land Mammal Age. The remains include an incomplete skull (braincase, auditory region, and nearly full dentition) and the atlas. Based on comparative studies of the anatomy of the auditory region, we describe 2 morphologies for the subfamily Eumegamyinae, 1 characterized by a short meatus acusticus externus, a great development of the foramen stylomastoideum, and a conspicuous ectotympanic cavity, and a 2nd characterized by a long meatus acusticus externus and lack of the ectotympanic fossa. The potential taxonomic and systematic value of the auditory region in Dinomyidae is discussed.

New associated cranial and postcranial remains of a new genus and species of Mylodontinae: Lestobradys sprechmanni, gen. et. sp. nov (Mammalia: Xenarthra), were found on the coast of Kiyu beach (San Jose, southern Uruguay). The specimens described are from the late Miocene (Huayquerian SALMA) sediments of Camacho Formation. The mandibular configuration of this new taxon differs from all well-known members of the family in presenting a first alveolus strongly projected toward the labial region that is separated from the rest of the alveoli of the dental series by a marked diastema. It additionally differs in its combination of a subtriangular second alveolus, subquadrangular third alveolus, and a bilobed last alveolus. An incomplete skull, three thoracic vertebrae, and two caudal vertebrae were associated with the mandibular remains. We also refer a complete and well-preserved right astragalus to the new species. Aspects of the history, systematics, and taxonomy of the Mylodontidae and their propo...

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.

ResumenEn el apéndice de su articulo reciente, Bracco (2006:511-540) realiza una serie de comentarios e interpretaciones de la evidencia científica interdisciplinaria producida por nuestro equipo en el sitio de Los Ajos en el sureste de Uruguay. Entre otras cosas, Bracco nos imputa: (a) de haber retrocedido la problemática de investigación en el área veinte años atrás, (b) de desconocer los trabajos anteriores realizados en la región, (c) de forzar nuestros datos paleoambientales a la secuencia cultural, y (d) de alegar, sin evidencia, la naturaleza doméstica de los montículos durante el período Montículo Precerámico en Los Ajos. En este comentario, nosotros respondemos a las alegaciones de Bracco.

The Sopas Formation is a late Pleistocene continental unit that includes trace fossils, woods, fresh-water mollusks, and vertebrates with mammals being the predominant taxa. Likely, relationships with the Last Interglacial Stage or with the Last Interstadial were proposed. The paleontological content of the Sopas Formation is updated, and the climatic and environmental signals provided by the fossil content are evaluated. Radiocarbon AMS dates ranging from 33,560 ± 700 year B.P. (cal 36,089 − 39,426 year) to 39,900 ± 1,100 (cal 42,025 − 45,389 year) and TL/OSL ages from 27,400 ± 3,300 to 71,400 ± 11,000 year (being the 45–28 ka time interval better represented), support a relationship with Marine Isotopic Stage 3 (MIS 3) in most outcrops. In the fossil assemblage are taxa that indicate open habitats, savannahs, and woodlands including gallery forests and perennial rivers; living representatives of taxa related to benign climatic conditions (mostly tropical to temperate climates), some taxa that suggest arid to semiarid environments, migrants, and seasonality indicators. A replacement versus mixed faunal models is discussed in the light of available evidence.

The xenarthrans of the sloth subfamily Mylodontinae are conspicuous members of South and North American Neogene faunas. They occupied a large latitudinal range from central North America to Tierra del Fuego in the austral extreme of South America (Latorre, 1998). The first undoubted representative of the subfamily is Glossotheriopsis pascualli, from the Friasian SALMA (middle Miocene) of Argentina. Beginning in the late Miocene (Huayquerian SALMA) the mylodontines are represented by numerous taxa that exhibit a range of morphological heterogeneity (Esteban, 1988) in contrast to the other subfamilies. Most of the mylodontine taxa described for the Neogene are based on very poor or fragmentary material making a comprehensive comparative description of the genera within the subfamily difficult. The best and most useful single bone that can be used to characterize mylodontid species is the mandible as it is commonly preserved and contains a complex suite of characters that makes it systematically informative (Perea, 1992). It is for these reasons that the majority of the Neogene sloth taxa are based on mandibular remains as they do allow an adequate morphologic comparison and subsequent phylogenetic conclusions that document the diversity within this subfamily of sloths. In this work we describe a right mandibular ramus originating from the Camacho Formation at Kiyu beach, Department of San Jose, Uruguay (Fig. 1). While the fossil shows some affinities with Pleistocene genera it also shares characters with older mylodontines as well. On the basis of its distinctive suite of morphological features it can be distinguished from all other known mandibular morphologies within the subfamily, indicating it represents a new genus and species. The material described here is deposited at the Paleontological Collection of Vertebrates, Facultad de Ciencias, Uruguay (FCDPV).

We describe Pseudoseisuropsis cuelloi, a new fossil furnariid from the upper Pleistocene of Uruguay, and investigate its phylogenetic relationships. Results of a cladistic analysis using 52 osteological characters from 29 taxa, including the extinct Pseudoseisuropsis nehuen, were consistent with placing the new species in the genus Pseudoseisuropsis. We conclude that the skull of Pseudoseisuropsis was prokinetic, although the shape of the nostrils was like a typical schizorhinal and rhynchokinetic furnariid. This observation reveals the inadequacy of the traditional categories of nasal types in characterizing the diversity of morphologies found in skulls of the Furnariidae. Finally, the analysis did not support a close relationship between Pseudoseisuropsis and Pseudoseisura, as previously thought, but suggests that Pseudoseisuropsis either belongs to the Dendrocolaptinae, or represents a more basal lineage within the Furnariidae. Un Nuevo Furnárido Fósil del Pleistoceno de Uruguay, con Observaciones sobre Tipos Nasales, Quinesis Craneal y Relaciones Filogenéticas del Género Extinto Pseudoseisuropsis Resumen. En el presente estudio se describe a Pseudoseisuropsis cuelloi, una nueva especie fósil de Furnariidae del Pleistoceno superior de Uruguay, y se investigan sus relaciones filogenéticas. El resultado de un análisis cladístico con 52 caracteres osteológicos y 29 taxa, incluyendo el ejemplar tipo de Pseudoseisuropsis nehuen es consistente con la inclusión de la nueva especie en el género Pseudoseisuropsis. Se concluye que el movimiento craneal de Pseudoseisuropsis era proquinético, a pesar de que la forma de las aberturas nasales es similar al de un típico furnárido esquizorrino/rincoquinético. Esta aparente contradicción pone en evidencia que las categorías tradicionales de tipos nasales son poco adecuadas para caracterizar la diversidad morfológica del cráneo en los Furnariidae. Por último, el análisis filogenético revela que Pseudoseisuropsis no esta estrechamente emparentado con Pseudoseisura, como fuera propuesto originalmente, sino que sugiere su inclusión en Dendrocolaptinae o en un linaje más basal dentro de la familia Furnariidae.

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

Extant sloths are represented by only two genera (Bradypus and Choloepus) both of which are semi-arboreal, slow-moving mammals. However, fossil Bradypoda are much more diverse and were traditionally considered to be “ground sloths,” although some of them are now recognized as having been arboreal. This group was well represented in the American Pleistocene fauna and among the larger representatives of the extinct sloths is the genus Megatherium with a body mass of 4 to 6 tons (Farina and Blanco, 1996; Farina et al., 1998). In this work we studied the middle-ear morphology of two Pleistocene taxa of the Mylodontidae family: Glossotherium robustum with an estimated body mass of 1500 kg and Lestodon armatus with an estimated body mass of 4100 kg (Bargo et al., 2000). In the mammalian middle-ear, sound energy is transferred from the external auditory meatus to the cochlea. The bone mechanism responsible for this transfer acts as a transformer allowing the low impedance of the auditory meatus to be matched to the much higher impedance of the cochlear fluid. The sound is transmitted from the tympanic membrane to the cochlea by the three middle-ear ossicles: the malleus, the incus, and the stapes. Impedance is composed of resistance and reactance forces. The main resistive component of the ear is related to the viscosity of the inner ear fluid causing resistance against the motion of the stapes footplate and to a lesser degree, the friction caused by the moving components of the middle ear. Two types of reactance are involved in middle-ear impedance (Plassmann and Brandle, 1992; Webster and Plassmann, 1992 and references therein). One is the mass reactance that is due to the mass of middle-ear structures. This mass reactance affects high frequencies more than low frequencies, so the impedance due to mass reactance increases with increasing frequency. The other reactance component of the middle-ear is the spring-like property of the ligaments and muscles. This spring reactance mainly affects low frequencies. At the ideal frequency range these two reactive components (mass and spring) partially cancel each other, and the resistive component, which does not vary with frequency, dominates the middle-ear impedance. Therefore, larger middleear ossicles, producing high mass-reactance, are well adapted to transfer low frequency signals (Plassmann and Brandle, 1992

The discovery of an exceptionally well-preserved skull permits the description of the new South American fossil species of the rodent,Josephoartigasia monesisp. nov. (family: Dinomyidae; Rodentia: Hystricognathi: Caviomorpha). This species with estimated body mass of nearly 1000 kg is the largest yet recorded. The skull sheds new light on the anatomy of the extinct giant rodents of the Dinomyidae, which are known mostly from isolated teeth and incomplete mandible remains. The fossil derives from San José Formation, Uruguay, usually assigned to the Pliocene–Pleistocene (4–2 Myr ago), and the proposed palaeoenvironment where this rodent lived was characterized as an estuarine or deltaic system with forest communities.

Multidisciplinary investigations at the Los Ajos archaeological mound complex in the wetlands of southeastern Uruguay challenge the traditional view that the La Plata basin was inhabited by simple groups of hunters and gatherers for much of the pre-Hispanic era1,2,3,4. Here we report new archaeological, palaeoecological and botanical data indicating that during an increasingly drier mid-Holocene, at around 4,190 radiocarbon (14C) years before present (bp), Los Ajos became a permanent circular plaza village, and its inhabitants adopted the earliest cultivars known in southern South America. The architectural plan of Los Ajos during the following Ceramic Mound Period (around 3,000–500 14C yr bp) is similar to, but earlier than, settlement patterns demonstrated in Amazonia5,6,7,8,9,10, revealing a new and independent architectural tradition for South America.

Nopachtus Ameghino is a poorly known genus of glyptodontid. The genus includes 2 species recorded in Argentina: Nopachthus coagmentatus Ameghino, from Brochero Formation (Montehermosian-Chapadmalalian, Early Pliocene-Late Pliocene) of Sierras de Córdoba/El Polvorín Formation (Upper Chapadmalalian, Pliocene) of Sierras Bayas de Olavarría, Buenos Aires province, and Nopachthus cabrerai Zamorano, Scillato-Yané, González-Ruiz and Zurita, from Monte Hermoso Formation (Montehermosian, Early Pliocene) from SO of Buenos Aires province. The knowledge about the presence of Nopachtus outside Argentina, is due to Toriño y Rinderknecht (2005), who mention one osteoderm which possesses similar characters to those of Nopachtus and Panochthus intermedius Lydekker. Later, Toriño y Perea (2008) resume this consideration. In this paper, the materials referred to Nopachtus in Uruguay are studied. There are 2 isolated osteoderms corresponding to the dorsal carapace: FC-CVF 1825 and CF-CVF 2759, both from Camacho Formation (Late Miocene) or Raigón Formation (Late Miocene-Middle Pleistocene) of the coast cliffs of San José Departament, Uruguay. Due to the great similarity of these osteoderms to those of Nopachtus, and according to the comparative analysis conducted, both are assigned to the present genus, thus expanding the geographic distribution of this taxon to Uruguay., Nopachtus Ameghino es un género de gliptodóntido poco conocido. Cuenta con 2 especies registradas para Argentina: Nopachtus coagmentatus Ameghino, de la formación Brochero (Montehermosense-Chapadmalalense, Plioceno Temprano-Plioceno Tardío) de las sierras de Córdoba/formación El Polvorín (Chapadmalalense Superior, Plioceno) de las sierras Bayas de Olavarría, provincia de Buenos Aires; y Nopachtus cabrerai Zamorano, Scillato-Yané, González-Ruiz y Zurita, de la formación Monte Hermoso (Montehermosense, Plioceno Temprano) del SO de la provincia de Buenos Aires. El conocimiento sobre la presencia de Nopachtus fuera de Argentina se debe a la mención de Torino˜ y Rinderknecht (2005) de un osteodermo que posee características semejantes a Nopachtus y a Panochthus intermedius Lydekker; posteriormente, Torino˜ y Perea (2008) retoman esta consideración. En la presente contribución se realiza un estudio de materiales referidos a Nopachtus en Uruguay. Se trata de 2 osteodermos aislados correspondientes a la coraza dorsal: FC-CVF 1825 y FC-CVF 2759, ambos proceden de la formación Camacho (Mioceno Tardío) o formación Raigón (Mioceno Tardío-Pleistoceno Medio) de las barrancas costeras del departamento de San José, Uruguay. Dada la notoria semejanza de estos osteodermos con los de Nopachtus, y por comparaciones realizadas, se asignan al citado género, ampliándose así la distribución geográfica del taxón a Uruguay., Facultad de Ciencias Naturales y Museo