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The avian fossil record of southern Brazil is scarce, consisting of few isolated remains. Here is described a ciconiid fossil from the assemblage of mammalian remains of the Santa Vitoria Formation (SVF). The specimen is a cervical vertebra morphologically similar to Ciconia maguari (maguari stork), common in southern Brazil today. Nevertheless, its larger dimensions suggest that it could be either a morphotype of that species or another, extinct species. The taphonomic modifications of the vertebra result of a combination of autogenic and allogenic factors including the aquatic habit, shape and transportation by flowing water and burial in a shallow stream. The fossil-bearing sediment dated by luminescence was deposited during the late Pleistocene, at 37.9 ka b2k, and exhibits physical features indicating deposition under variable discharge and seasonal oscillations of the water table. The presence of an aquatic bird in these sediments indicates a period of increased precipitation, chronocorrelated to one of the millenial-scale warming pulses recorded in ice cores from Antarctica (Antarctic Isotope Maxima) that characterized the interstadial MIS 3. On the other hand, the dry and cold climate of the following glacial MIS 2 may have forced ciconiids and aquatic mammals to retreat to suitable areas (refugia), as indicated by their absence in the loess deposits (Cordao Formation) overlying the SVF, until returning during the Holocene when climate became wet and warm again. The results presented here increase the avian fossil record of southern Brazil and help understand the role of climate change on the distribution of ciconiid birds and other taxa during the Quaternary in southern South America.

Megamammals constituted an important component in the Pleistocene faunal communities of South America. Paleobiological and paleoecological studies involving different megamammal taxa have increased significantly in the last years, but there are still several poorly-known issues of its life history. In this work, we analyze an assemblage composed of 13 individuals of different ontogenetic stages, and possibly different sex, belonging to the giant ground sloth Lestodon armatus (Xenarthra, Folivora), recovered from Playa del Barco site (Pampean Region, Argentina). A dating of 19,849 years Cal BP allows assigning this assemblage to a period of the MIS (Marine Isotope Stage) 2 related to the end of the Last Glacial Maximum. Based on multiple lines of research (e.g. taphonomy, paleopathology, osteohistology, isotopy), we interpret the origin of the assemblage and diverse paleobiological and paleoecological aspects (e.g. social behavior, ontogenetic changes, sexual dimorphism, diseases, resource and habitat use, trophic relationships) of L. armatus. Evidence suggests that the assemblage was formed by a local single event of catastrophic mortality, which affected different members of a social group. This record represents the first accurate evidence of gregariousness for this ground sloth, providing new data on a poorly-known behavior among extinct Folivora., The research was supported by the scientific projects 06G Facultad de Ciencias Exactas y Naturales (UNLPam), National Geographic-Waitt Foundation #W467-16, CGL2016-79334-P, and PGC2018-094955-A-I00 of the Spanish Ministry of Science, Innovation and Universities. This is a contribution of the research group UCM 910607 on Evolution of Cenozoic Mammals and Continental Palaeoenvironments, CSIC-i-COOP project COOPB-20287.

Modifications on the cheek teeth and dentary bone (loss of dental tissues on the extra-alveolar portion of the cheek teeth, and corrosion on the surface of the dentary bone) of fossil specimens of medium to giant South American rodents (mainly neoepiblemids) from the Neogene (Brazil and Argentina) are documented here. These features are similar to those observed in teeth and bones of small hypsodont rodents (recent and Quaternary fossils) that were subjected to digestive process by predators/scavengers. Based on comparisons, we tentatively hypothesize that acid-etching resulting from digestive processes could have caused the modifications in the specimens, providing evidence of a palaeoecological interaction between neoepiblemids (and other rodents), and predators or scavengers.

The non-dinosaurian dinosauriform silesaurids are the closest relatives of crown-group dinosaurs and are thus, important for understanding the origins of that group. Here, we describe the limb bone histology of the Late Triassic silesaurid Sacisaurus agudoensis from the Candelária Sequence of the Santa Maria Supersequence, Rio Grande do Sul state, Brazil. The sampled bones comprise eight femora and one fibula from different individuals. The microscopic analysis of all elements reveals uninterrupted fibrolamellar bone tissue indicating rapid growth. A transition to slower growing peripheral parallel-fibered bone tissue in some individuals indicates a decrease in growth rate, suggesting ontogenetic variation within the sample. The osteohistology of Sacisaurus agudoensis is similar to that of other silesaurids and supports previous hypotheses that rapid growth was attained early in the dinosauromorph lineage. However, silesaurids lack the complex vascular arrangements seen in saurischian dinosaurs. Instead, they exhibit predominantly longitudinally-oriented primary osteons with few or no anastomoses, similar to those of some small early ornithischian dinosaurs. This simpler vascular pattern is common to all silesaurids studied to date and indicates relatively slower growth rates compared to most Dinosauria.

The fossil-bearing stratigraphic sections of the Solimoes Formation (southwestern Brazilian Amazonia) are exposed mainly along the Jurua, Purus, and Acre rivers, and in road cuts. These deposits have provided fossils of the four main lineages of Caviomorpha – Cavioidea, Erethizontoidea, Octodontoidea, and Chinchilloidea, contributing to the understanding on the evolution of tropical Neogene rodents. Herein, our knowledge about fossil rodents from this region is reviewed. New specimens are recorded, including taxa mentioned for this region for the first time, such as basal cavioids, Dolichotinae, Caviodon (Hydrochoeridae), and Drytomomys (Dinomyidae). Unfortunately, the deposits have no absolute ages, and based on palynological data and the biochronology of several taxa (mainly mammals), the encompassed fauna has been constrained to the late Miocene. However, some rodent lineages recorded here seem to be more related to older faunas, from the middle Miocene and Paleogene. Regarding the biogeographic and paleoenvironmental affinities, most of the Neogene rodents from the Acre region show more similarities to those from the Entre Rios, Argentina, and Urumaco, Venezuela, where wet environments were present during Neogene times. An increase in prospecting along southwestern Amazonian rivers looking for rodents (among other vertebrates) associated with methods to better constrain the ages of these faunal assemblages will contribute to a better understanding of the evolution of the tropical rodents as well as the stratigraphy and age of that portion of the basin.

Here are described post mortem modifications (pseudopaleopathologies) in 762 specimens of extinct mammals from three middle to late Pleistocene assemblages (Campanha, Chui Creek and continental shelf) of the state of Rio Grande do Sul, southern Brazil. These assemblages include mostly large-sized herbivores preserved in fluvial facies, although the assemblage from the shelf consist of remains that were reworked several times by sea-level oscillations. Although some patterns of modification are similar between the assemblages (e.g. post-fossilization plain fractures), others such as the grade of abrasion or weathering varies according to the depositional setting. The scarcity of modifications that could be attributed to predators or scavengers indicate that carnivory was not a major process driving the formation of the assemblages. Most of the fossils from the Campanha are complete, but a relatively high proportion of them exhibits advanced stage of weathering, whereas those from Chui Creek and the continental shelf are mostly unweathered. Most of the remains from the Campanha and Chui Creek are unabraded, whereas all fossils from the shelf were subject to abrasion. Few fossils exhibit signs of modification by organisms such as plants and insects. Fossils from the continental shelf have crusts of beach rock, and some specimens from the Campanha and Chui Creek have crusts of calcium carbonate or iron oxide. Besides the abrasion, the main difference between fossils from the continental and marine assemblages is the dark color and higher mechanical resistance of the latter. This difference is related to post depositional geochemical processes in the marine environment. The chemical composition of fossils from Chui Creek and continental shelf was qualitatively analyzed using energy dispersive X-ray spectrometry (EDX) and compared with recent bones. The results show the presence in the fossils of several elements not found in recent bones, incorporated through diagenetic processes controlled by specific conditions of each depositional environment.

Sacisaurus agudoensis is the only silesaurid known from the Triassic beds of the Santa Maria Supersequence and the correlation of its type locality to the other Triassic deposits of south Brazil has always been controversial. In an attempt to improve this, a handful of dinosaur and cynodont remains found associated to S. agudoensis are here described and compared. The anatomy of the sauropodomorph is more similar to that of Norian forms such as Pantydraco caducus and Unaysaurus tolentinoi than to that of Carnian taxa such as Saturnalia tupiniquim and Pampadromaeus barberenai. The cynodonts recovered based on isolated teeth include a brasilodontid and a Riograndia-like form. This assemblage is consistent with a Norian age, as is also suggested by local stratigraphic correlation, which positions the site in the Caturrita Formation. O Sacisaurus agudoensis é o único silesaurídeo conhecido dos leitos Triássicos da Supersequência Santa Maria e da a correlação de sua localidade-tipo com os demais depósitos triássicos do sul do Brasil sempre foi controversa. Numa tentativa para melhorar isto, são aqui descritos alguns restos de dinossauros e cinodontes encontrados associados a S. agudoensis e comparado. A anatomia do sauropodomorfo é mais semelhante à das formas Norian, como Pantydraco caducus e Unaysaurus tolentinoi do que aos táxons Carnianos como Saturnalia tupiniquim e Pampadromaeus barberenai. Os cinodontes recuperados com base em dentes isolados incluem um brasilodontídeo e uma forma do tipo Riograndia. Esta montagem é consistente com uma idade Norian, como também é sugerido pela correlação estratigráfica local, que posiciona o sítio no Formação Caturrita.

Mesosauridae comprises the oldest known aquatic amniotes which lived in Gondwana during the Early Permian. Previous work in the Uruguayan mesosaur-bearing Mangrullo Formation suggested that mesosaurids lived in an inland water body, inferred as moderately hypersaline, with exceptional preservational conditions that justified describing these strata as a Fossil-Lagerstatte. Exquisitely preserved articulated mesosaur skeletons, including gastric content and associated coprolites, from the Brazilian Irati Formation in the State of Goias (central-western Brazil) indicate excellent conditions of preservation, extending the Konservat-Lagerstatte designation to both units in the Parana Basin. The near-absence of more resistant fossil remains, like actinopterygian and temnospondyl bones, demonstrates the faunistic poverty of the mesosaur-bearing “salty sea”. Our studies of the alimentary habits of mesosaurids through the use of stereoscopic microscopy, light and electronic microscopy, and X-ray diffractometry suggest that the diet of mesosaurids was predominantly composed of pygocephalomorph crustaceans (possibly not exceeding 20 mm in length). However, the presence of bones and bone fragments of small mesosaurs in the gastric content, cololites, coprolites, and possible regurgitalites may also indicate cannibalistic and/or scavenging habits. Cannibalism is relatively common among vertebrates, particularly during conditions of environmental stress, like food shortage. Likewise, the apparent abundance of pygocephalomorph crustacean fossils in the Irati and Mangrullo Formations, outside and within the studied gastric, cololite, and coprolite contents, might have to do with environmental stress possibly caused by volcanic activity, in particular ash spread into the basin during the Early Permian. In this context, casual necrophagy on the dead bodies of small mesosaurs and large pygocephalomorphs might have been an alternative alimentary behavior adopted for survival in mesosaurs.

The earliest undisputed crown-group amniotes date back to the Late Carboniferous, but the fossil record of amniotic eggs and embryos is very sparse, with the oldest described examples being from th...

In their monograph Review of the Pelycosauria, Romer and Price (1940), proposed that the earliest synapsids (“pelycosaurs”) were cosmopolitan, despite the observation that amniotes appeared to be restricted to the paleotropics during the Late Carboniferous and Early Permian (290–282 Ma). Romer and Price (1940) accounted for the scarcity of terrestrial tetrapods, including “pelycosaurs,” in Lower Permian beds elsewhere to the absence of coeval continental deposits beyond North America and Europe. Indeed, most workers recognized a geographical and temporal gap between Permo-Carboniferous “pelycosaurs” and therapsid synapsids. Recent research has confirmed that varanopid and caseid “pelycosaurs” were components of therapsid-dominated Late Permian faunas preserved in Russia and South-Africa (Tatarinov and Eremina, 1975; Reisz, 1986; Reisz et al., 1998; Reisz and Berman, 2001). In this note, we report the first record of basal synapsids for South America (Fig. 1) and discuss its paleogeographic and temporal implications. These remains come from outcrops assigned to the Buena Vista Formation (Goso et al., 2001; Fig. 2), which filled part of the Parana Basin during Late Permian and probably Early Triassic (Bossi and Navarro, 1991). The Parana Basin is one of the major sedimentary basins of Gondwana, covering an area of nearly 1.5 million km2, in Brazil, Argentina, Paraguay and Uruguay (Franca et al., 1995; Zalan et al., 1990). At the beginning of basin development the Devonian marine and brackish conditions prevailed, but subsequently, during the Late Permian, there was a gradual change to continental sedimentation and the deposition of fossil-bearing red beds. Buena Vista Formation is characterized by reddish fine sandstone interbedded with lenticular clay layers and intraformational conglomerates (Fig. 2), (Bossi and Navarro, 1991; Goso et al., 2001). The paleoenvironment is related to the final withdrawal of the sea, and the upper part of this …