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Mesosaurs are basal amniotes that lived at the beginning of the Permian or close to the Permo–Carboniferous boundary. Despite the several hundred specimens that have been found, including complete skeletons of adult and juvenile individuals, mesosaur taxonomy has been subjected to a high controversy over time. Currently, three monotypic genera, Mesosaurus tenuidens Gervais, Stereosternum tumidum Cope, and Brazilosaurus sanpauloensis Shikama & Ozaki are recognized, but identification of new specimens using the available diagnostic characters are arbitrary and influenced by high subjectivity. We performed anatomical and morphometric analyses to look for statistical support to these previously suggested basic diagnostic characters through an exhaustive anatomical revision of these characters and also of some new attributes discovered during the course of our study. We found a notable influence of taphonomic features in most of the diagnostic characters used to differentiate the three monotypic genera, including strong bias derived from the preservation of individuals in different ontogenetic stages, whose size and degree of ossification could have been controlled by particular environmental conditions that resulted in subtle polymorphisms of these and other few characters. Other features may even represent sexual dimorphism. After the detailed revision of the type specimens of the three currently acepted mesosaur taxa, for which we include here good-quality photographs, and considering the lack of statistical support for the most applied putative diagnostic features such as the different ratio found when comparing skull and cervical region lengths and the low or higher intensity of pachyosteosclerosis observed in dorsal ribs, which can be controlled by taphonomic and ecological conditions, we recognize Mesosaurus as the only mesosaurid taxon in the Parana and Karoo basins, probably including dwarf individuals. Therefore, S. tumidum and B. sanpauloensis are suggested here as nomina dubia taking into account that the autapomorphies that supported these taxa cannot be confirmed to be absent in Mesosaurus. Keywords: Mesosaurus, morphometrics, taxonomy, ?Early Permian, Gondwana. RESUMO – Mesossauros sao amniotas basais que viveram no inicio do Permiano ou proximo ao limite Permo–Carbonifero. A despeito das centenas de especimes encontrados, incluindo esqueletos completos de individuos adultos e juvenis, a taxonomia dos mesossaurostem sido tema de muita controversia ao longo do tempo. Hoje, tres generos monotipicos, Mesosaurus tenuidens Gervais, Stereosternum tumidum Cope, e Brazilosaurus sanpauloensis Shikama & Ozaki sao reconhecidos, mas a identificacao de novos especimes utilizando oscaracteres diagnosticos disponiveis e arbitraria e influenciada por alta subjetividade. Nos realizamos analises anatomica e morfometrica, tendo em vista obter um suporte estatistico para estes caracteres sugeridos como diagnosticos basicos por meio de uma exaustiva revisao anatomica destes caracteres, e de alguns novos caracteres descobertos durante o desenvolvimento de nosso estudo. Nos notamos uma notavel influencia de fatores tafonomicos na maioria dos caracteres diagnosticos utilizados para os tres taxons monotipicos e incluindo uma forte preconcepcao derivada da preservacao dos individuos em diferentes estagios ontogeneticos, cujos tamanho e grau de ossificacao poderiam ser controlados por condicoes ambientais que resultaram em sutis polimorfismos destes poucos caracteres. Outros aspectos podem mesmo representar dimorfismo sexual. Considerando a falta de suporte estatistico para a maioria dos putativos caracteres diagnosticos, tais comoas diferentes relacoes entre comprimento do crânio e da coluna cervical e a pressao das condicoes tafonomicas e ecologicas, que podem ter controlado um menor ou maior grau de paquiosteoesclerose nas costelas dorsais, nos reconhecemos Mesosaurus como o unico taxonde mesosaurideo nas bacias do Parana e Karoo, provavelmente incluindo populacoes anas, e sugerimos que S. tumidum e B. sanpauloensis devem ser considerados como nomen dubium, levando em conta que as autapomorfias que suportam estes taxons nao podem ser confirmadas como nao estando presentes em Mesosaurus. Palavras-chave: Mesosaurus, morfometria, taxonomia, ?base do Permiano, Gondwana.

Made available in DSpace on 2021-06-25T11:02:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Dinosaurs possess a form of tooth attachment wherein an unmineralized periodontal ligament suspends each tooth within a socket, similar to the condition in mammals and crocodylians. However, little information is known about tooth attachment and implantation in their close relatives, the silesaurids. We conducted a histological survey of several silesaurid taxa to determine the nature of tooth attachment in this phylogenetically and paleoecologically important group of archosaurs. Our histological data demonstrate that these early dinosauriforms do not exhibit the crocodilian/dinosaur condition of a permanent gomphosis, nor the rapid ankylosis that is plesiomorphic for amniotes. Instead, all sampled silesaurids exhibit delayed ankylosis, a condition in which teeth pass through a prolonged stage where the teeth are suspended in sockets by a periodontal ligament, followed by eventual mineralization and fusion of the tooth to the jaws. This suggests that tooth attachment in crocodylians and dinosaurs represent the further retention of an early ontogenetic stage compared to silesaurids, a paedomorphic trend that is mirrored in the evolution of synapsid tooth attachment. It also suggests that the dinosaur and crocodylian gomphosis was convergently acquired via heterochrony or, less likely, that the silesaurid condition represents a reversal to a plesiomorphic state. Moreover, if Silesauridae is nested within Ornithischia, a permanent gomphosis could be convergent between the two main dinosaur lineages, Ornithischia and Saurischia. These results demonstrate that dental characters in early archosaur phylogenies must be chosen and defined carefully, taking into account the relative duration of the different phases of dental ontogeny. Departamento de Biologia Universidade de São Paulo Department of Biological Sciences University of Alberta Faculty of Dentistry Oral & Craniofacial Sciences King's College London Department of Geosciences Virginia Tech Programa de Pós-Graduação em Biologia Animal Instituto de Biociências Letras e Ciências Exatas UNESP Campus de São José do Rio Preto Natural History Museum of Utah and Department of Geology & Geophysics University of Utah Laboratório de Estratigrafia e Paleobiologia Departamento de Geociências Universidade Federal de Santa Maria Museu de Ciências Naturais Secretaria do Meio Ambiente e Infraestrutura Programa de Pós-Graduação em Biologia Animal Instituto de Biociências Letras e Ciências Exatas UNESP Campus de São José do Rio Preto

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.

The Sanga do Cabral Formation of southern Brazil has a rich fossil tetrapod assemblage and is suggested to have an Early Triassic age mainly based on the presence of the parareptile Procolophon trigoniceps . However, a Permo-Triassic age can be also suggested for this unit taking into account the presence of putative Permian taxa and some previous stratigraphic assessments. We describe here several large vertebrae from the Sanga do Cabral Formation that display a distinctive morphology that includes the presence of a transverse distance across postzygapophyses more than twice the transverse width of the centrum, and accessory articulation structures in the neural arch that remind the hyposphene and hypantrum present in some basal parareptiles and diadectomorphs. Vertebrae with a similar large size and morphology had been previously reported from the same locality as belonging to the genus Procolophon based on their parareptile appearance (mainly the presence of a swollen neural arch) and the fact that the vertebrae were collected at the same locality where a large fragmentary skull assigned to this taxon was found. However, these vertebrae lack a comparable consistent morphology with those of Procolophon and basic statistical analyses demonstrate that these vertebrae are significantly larger than those expected in the largest known Procolophon skulls of South Africa. The morphology of these vertebra is consistent with that present in seymouriamorphs, pareiasaurs and diadectomorphs, but the absence of exclusive diagnostic characters precludes an assure assignation to either of these taxa. According to their current stratigraphic range, seymouriamorphs are the most plausible postulation, as their younger representatives are known from Late Permian deposits of Russia, but the other candidates cannot be excluded. The presence of any representative of those groups in the Sanga do Cabral Formation would be important because: (1) they would represent the first and only known record of seymouriamorphs or diadectomorphs in Gondwana, regarding the characters that the described vertebrae share with these groups; (2) they would suggest a survivorship for pareisaurs up to the Latest Permian or through the Permian-Triassic boundary, according to geochronological data currently available for this unit; (3) they might also suggest a Late Permian age for at least part of the Sanga do Cabral Formation if the intraformational conglomerates that yielded the vertebrae resulted from the rejuvenation of older levels of the same unit, and they do not include reworking of stratigraphically older strata.

O presente trabalho apresenta a descrição comparativa de crânio, pós-crânio e osteodermos do Dasypodini (Xenarthra, Cingulata) MNRJ 552-V, proveniente dos depósitos quaternários da Gruta de Itaporanga, Sorocaba-SP. Seu crânio foi tomografado e comparado àqueles de táxons viventes, de modo a abarcar as três subfamílias de Dasypodidae, enquanto seu pós-crânio foi comparado ao de Dasypus novemcinctus. Ademais, como MNRJ 552-V foi inicialmente descrito como pertencente a Propraopus punctatus, foram analisados materiais, especialmente osteodermos, atribuídos a este gênero depositados em coleções paleontológicas brasileira e argentinas. Para definir as relações do referido espécime com outros Dasypodini, um estudo filogenético foi realizado. Além de MNRJ 552-V, o grupo interno abarcou cinco unidades taxonômicas operacionais (OTUs), incluindo duas espécies viventes de Dasypus, dois espécimes atribuídos a P. grandis, bem como parte do material tipo de Dasypus sulcatus Lund, 1842, proveniente de Lagoa Santa-MG, tendo exclusivamente este sido analisado apenas por meio da literatura. O grupo externo, definido com base em estudos filogenéticos prévios, inclui Stegotherium tesselatum e Cabassous tatouay. Nesta análise, os osteodermos, que figuram historicamente como de grande relevância sistemática para Cingulata, igualmente mostraram-se fundamentais para diferenciar as OTUs do grupo interno. A única árvore mais parcimoniosa obtida por meio de busca exata sugere maior proximidade de MNRJ 552-V às espécies viventes de Dasypus, parecendo preferível atribuir tal espécime a D. punctatus Lund, 1840, o que coincide com a proposta nomenclatural original da espécie. Já o outro clado, que consiste de uma politomia com três outras OTUs, por incluir materiais referidos à espécie tipo do gênero (P. grandis) foi nomeado Propraopus. Deste modo, a OTU Dasypus sulcatus deve ser tratada como Propraopus sulcatus. A politomia que forma clado Propraopus corrobora a difícil distinção entre materiais P. sulcatus e P. grandis, previamente apontada por diversos autores. This work presents the comparative description of the skull, postcranium and osteoderms of the Dasypodini (Xenarthra, Cingulata) MNRJ 552-V, collected in the quaternary deposits of Gruta de Itaporanga, Sorocaba-SP, Brazil. The skull was CT scanned and compared to those of extant taxa of all three Dasypodidae subfamilies, while the postcranium was compared to that of Dasypus novemcinctus. Given that MNRJ 552-V was originally described as Propraopus punctatus, it was compared to fossils (especially composed of osteoderms) attributed to this genus in paleontological collections of Brazil and Argentina. In order to define the relations of the described specimen to other Dasypodini, a phylogenetic study was performed. Along with MNRJ 552-V, the ingroup comprises five operational taxonomic units (OTUs), including two extant species of Dasypus, two specimens attributed to P. grandis, as well as part of the type material of Dasypus sulcatus Lund, 1842 from Lagoa Santa-MG, the latter solely analyzed based on the literature. The outgroup was defined based on previous phylogenetic studies and includes Stegotherium tesselatum and Cabassous tatouay. The osteoderms, which are skeletal parts historically relevant to Cingulata systematics, were also fundamental to differentiate the ingroup OTUs in the analysis. The single most parsimonious tree obtained with an exact search suggested that MNRJ 552-V is more closely related to the extant Dasypus species. Accordingly, it is preferable to attribute that specimen to D. punctatus Lund, 1840, following the original designation of the species. The sister clade of Dasypus, which consists of a polytomy with three other OTUs, was assigned to the genus Propraopus, once it includes material referred to its type species (P. grandis). Therefore, the OTU Dasypus sulcatus should be treated as Propraopus sulcatus. The polytomy that forms the Propraopus clade highlights the problem in differentiating P. sulcatus and P. grandis, as previously pointed by many authors.

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.

Enamel hypoplasia is characterized by reduction in the enamel thickness, resulting from a disruption of ameloblast activity due to systemic physiological stress. The euhypsodont teeth of Toxodon, a notoungulate from the Pleistocene of South America, often exhibit signs of enamel hypoplasia, in the form of continuous grooves or a series of pits where the enamel is thinner than in normal areas. These defects alternate with areas of normal enamel, and sometimes more than one form of enamel hypoplasia is present on the same tooth. This study analysed teeth of Toxodon from the Pleistocene Touro Passo Formation and the coastal plain of State of Rio Grande do Sul, Southern Brazil. Six types of enamel hypoplasia were observed. Upper teeth present mainly superficial grooves on the buccal surface, and the defects are less severe than those observed in the lower teeth. In the lower incisors, deep grooves with mesiodistal rows of pits were observed, showing clearly cyclical changes, which to a lesser degree, exist in all teeth. These changes are likely related to the continuous growth of euhypsodont teeth. Seven specimens were analysed under scanning electron microscopy and optical microscopy, which showed the occurrence of microstructural changes associated with the macroscopic enamel defects. Enamel underlying in the vicinity of hypoplastic defects was aprismatic and associated with prominent pathologic striae. These pathological findings might indicate that toxodonts were exposed to some stressing conditions or that their teeth were more easily abraded due to a change in diet items, related to shifting climatic conditions.

The comparative description of the most complete specimen of Dasypus punctatus (Xenarthra, Cingulata), from southeastern Brazil, reveals that the species differs from other Dasypodini by the numerous foramina it has in both buckler and movable osteoderms, providing the basis for the lectotype designation. This species was historically allocated to Propraopus, but the inclusiveness and monophyly of that genus are uncertain. A new phylogenetic analysis groups D. punctatus with the living species of Dasypus in a monophyletic clade for the genus, also supporting a Propraopus clade composed of P. sulcatus and the type species P. grandis. The palatal anatomy corroborates previously suggested affinities between D. kappleri and D. punctatus. On the contrary, the possible synonymy between P. grandis and P. sulcatus needs further investigation, given that they differed on a single character. As usual in cingulate systematics, characters related to osteoderm ornamentation proved essential to determine the r...

Unlike most rauisuchians, which are known based on partially preserved specimens, fossils attributed to Decuriasuchus quartacolonia include a monotaxonomic assemblage com- posed of nine associated individuals (MCN-PV10.105a-i), three with almost complete skulls (MCN-PV10.105a,c,d), and a partial disarticulated skull (MCN-PV10.004) collected in the Mid- dle Triassic (Ladinian, Dinodontosaurus Biozone) beds of the Santa Maria Formation, in south Brazil. Because of its completeness and possible phylogenetic position, as one of the most basal loricatans, D. quartacolonia is a key taxon for anatomic, evolutionary and biomechanical stud- ies of rauisuchians. The comparative description of its osteology reveals that the skull and mandi- ble of D. quartacolonia are very similar to those of cf. Prestosuchus chiniquensis and Saurosuchus galilei, sharing a drop-shaped subnarial fenestra, a subtriangular antorbital fenestra with an elon- gated and narrow anterior point, a 'roman nosed' nasal, and a posteroventrally oriented ridge on the lateral surface of the ventral ramus of the squamosal. Among the differences are the autapomor- phies of D. quartacolonia: numerous maxillary teeth (17), lateral expansion of the nasal/lacrimal covering the antorbital fenestra dorsally, and squamosal and quadratojugal forming a subtriangular projection that invades the lower temporal fenestra. The study of rauisuchians began in the middle of the 20th century, when the German palaeontolo- gist Friedrich von Huene discovered archosaur fossils in Brazil. Huene (1938b, 1942) described four new taxa currently considered as rauisuchians: Prestosuchus chiniquensis, Prestosuchus loricatus, Procerosuchus celer and Rauisuchus tiradentes. The generic name of the latter taxon, in honour of Guilherme Rau, a Brazilian-German dentist who collaborated with Huene, achieved family and class status in later works (e.g. Huene 1956; Krebs 1976; Bonaparte 1984; Parrish 1993; Brusatte et al. 2010; Nesbitt 2011). Since then, several fur- ther rauisuchian remains have been discovered in Brazil, including rather complete specimens such as that of cf. Prestosuchus chiniquensis (UFRGS-PV0156T; Barberena 1978). However, more recently, about 70 years after Huene's discov- eries, a new taxon was proposed (Franca et al. 2011a). Named Decuriasuchus quartacolonia, the taxon was based on a monotaxonomic assemblage

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...

The Early Permian mesosaurids are the oldest known aquatic amniotes with an exclusively Gondwanan distribution. Although several hundred of complete skeletons have been discovered and intensively studied, the anatomy and taxonomic composition of the group, as well as its phylogenetic relationships remain controversial. Several well-preserved mesosaurid specimens found in Uruguay justify a new anatomical reconstruction of the skull of Mesosaurus tenuidens, differing from earlier ones especially in the presence of a lower temporal fenestra. The significance of this structure for the evolution of temporal fenestration in amniotes is evaluated according to the two most recent phylogenetic hypotheses, in which mesosaurids are basalmost sauropsids or basalmost parareptiles. A synapsid-like fenestration may be the primitive condition for Amniota, and it may be also a basal condition for parareptiles, because recent phylogenies suggest a basal position for mesosaurids and lanthanosuchoids within that group, and both possess a lower temporal fenestra. Our results also give a moderately strengthened support for diapsid affinities of turtles.

For more than 30 million years, in early Mesozoic Pangea, "rauisuchian" archosaurs were the apex predators in most terrestrial ecosystems, but their biology and evolutionary history remain poorly understood. We describe a new "rauisuchian" based on ten individuals found in a single locality from the Middle Triassic (Ladinian) Santa Maria Formation of southern Brazil. Nine articulated and associated skeletons were discovered, three of which have nearly complete skulls. Along with sedimentological and taphonomic data, this suggests that those highly successful predators exhibited some kind of intraspecific interaction. Other monotaxic assemblages of Triassic archosaurs are Late Triassic (Norian-Rhaetian) in age, approximately 10 million years younger than the material described here. Indeed, the studied assemblage may represent the earliest evidence of gregariousness among archosaurs, adding to our knowledge on the origin of a behavior pattern typical of extant taxa.

A new species of Tapirus (Perissodactyla: Tapiridae) is described from the upper Pleistocene of the Rio Madeira Formation in Araras, Nova Mamore Municipality, Rondonia State, Brazil. Tapirus rondoniensis sp. nov. is represented by a nearly complete skull with a unique combination of characters that differ from those of extant and fossil species of Tapirus described from South America. It is diagnosed mainly by its broad frontals that bear a pneumatization extending to the frontoparietal suture, a high sagittal crest, a weakly molarized P2 lacking a protoloph, and a metaloph that merely reaches the base of the ectoloph. T. rondoniensis sp. nov. is similar in some respects to T. terrestris, but it retains some primitive dental and cranial character states in common with T. pinchaque, such as broad frontals and a weakly molarized P2.

A redescription of the extinct snake genus Colombophis is presented, on the basis of new specimens from the late Miocene of southwestern Brazilian Amazonia, and those previously reported for the middle Miocene of Colombia and Venezuela. The reappraisal of Colombophis allows the recognition of a new species, C. spinosus sp. nov. The revised diagnosis of the genus is based on the midtrunk vertebrae, distinct from those of other snakes mainly in the features of the neural arch, position and shape of the neural spine, inclination of the zygapophyses, shape of the centrum, and development of the haemal keel. The affinities of Colombophis with “Anilioidea” are still unresolved; it is distinguished from all known extinct and extant “anilioids” due to its great vertebral size and the frequent presence of paracotylar foramina. The posterior paired apophyses of the haemal keel in some vertebrae, and the high neural spine of C. spinosus also contrast significantly with the “anilioid” genera, making the allocation of the genus into this probably paraphyletic group not well supported. Here, we recognized Colombophis as a basal alethinophidian of uncertain relationships.

The Chiroptera do not have an extensive fossil record. To date, for the Quaternary of Brazil, only material from Minas Gerais, Sao Paulo, Bahia and Goias States are known. For Rio Grande do Sul State, in contrast to the studies about the Pleistocene megafauna, little is known about Holocene small mammals, this being the first contribution about the Chiroptera of this age found in Rio Grande do Sul. The material was excavated from two archaeological sites, dating from ± 9,400 yrs BP to ± 4,250 yrs BP. The taxa recorded were: Chrotopterus auritus, Pygoderma bilabiatum (Phyllostomidae); Eptesicus brasiliensis, E. fuscus, Myotis cf. Myotis ruber, Vespertilionidae aff. Lasiurus (Vespertilionidae); Tadarida brasiliensis, and Molossus molossus (Molossidae). The presence of E. fuscus extends its Holocene distribution far southwards into the south temperate zone; its previous Quaternary occurrences were in Bahia State, Brazil, as well as in Venezuela, Mexico and the USA.

The South American Teiidae fossil record is restricted to the Cenozoic, and the most conspicuous remains were found in Early to Late Miocene of Argentina and Middle Miocene of Colombia and Peru, all represented by Tupinambinae lizards. Here, we describe a right fragmentary dentary and one dorsal vertebra collected in the Solimoes Formation at the Talisma locality, situated on the Purus River, in the southwestern Brazilian Amazonia (Late Miocene). The material is tentatively conferred to the extinct genus Paradracaena. It represents the first record of lizards for the Neogene southwestern Brazilian Amazonia.

In the last few years, studies about climate successions in Rio Grande do Sul State (southern Brazil) during the Quaternary increased significantly, mostly due to palynological studies. The knowledge about Quaternary small mammals from Rio Grande do Sul is very poor. However, among the results obtained by archeological research there is an interesting collection of small mammals exhumated from rock shelter deposits. Here we describe the marsupial fauna found in two sites: Garivaldino and Sangao. Both sites are located at the boundary between two large Neotropical subregions, Chaco and Parana. Sediments from these two sites are from the early, middle, and part of the late Holocene. Additionally, we discuss paleobiogeographic, paleoenvironmental, and paleoclimatic aspects, on the basis of the seven taxa recorded: Gracilinanus microtarsus, G. agilis, Monodelphis americana, Thylamys velutinus, Thylamys cf. T. velutinus, Philander opossum, and Didelphis sp. Paleoenvironmental aspects inferred for both sites are consistent: the emergence of typical elements of the current Parana biogeographic subregion was probably established by the end of the early Holocene or the beginning of the middle Holocene. Conclusions are also coherent with the results previously obtained from palynological sequences in these same localities. The micro-marsupials sequence suggests that the environmental changes were not abrupt but gradual during the Holocene in Rio Grande do Sul State.

The Triassic of Southern Brazil is well-known for its rich tetrapod body fossils. However, trace fossils such as tetrapod trackways and trails were discovered only recently from the Predebon outcrop (upper part of the Alemoa Member, Santa Maria Formation), providing new information on small-sized animals. The trackways can be identified as Rhynchosauroides retroversipes isp. nov., Rhynchosauroides isp., Rhynchosauroides? isp. and drag marks produced by swimming animals of lacertoid affinity. The preservation of the tracks and trackways was influenced by the water level whilst they were being made and subsequent subaerial exposure. The trackmaker of R. retroversipes isp. nov. corresponds to a lacertoid quadruped tetrapod with primitive autopodia, a sprawling gait and possibly a long tail, whilst the pes was directed postero-laterally. The trackmaker may have been a climbing animal, with adaptations that include curved claws and reversion of the pes. On the ground this animal would have had a slow, lumbering locomotion, although it could attain higher speeds over short distances using a bipedal gait. These trackways can be attributed to lacertoid reptiles, possibly sphenodontids, whose skeletons are encountered in the Caturrita Formation, which overlies the Santa Maria Formation.

The South American Late Triassic offers the most comprehensive window to the early radiation of dinosaurs. This is enhanced by the discovery of Sacisaurus agudoensis, a new dinosauriform from the Caturrita Formation of Brazil. Various morphological features suggest its close phylogenetic affinity to Silesaurus, and both may be basal ornithischian dinosaurs. Sacisaurus has a pair of elements forming the tip of its lower jaw, hypothesized to be equivalent to the ornithischian predentary. This suggests that during an initial stage of their evolution, those dinosaurs had a paired predentary, which later fused into a single structure. As an originally paired bone, the predentary is comparable to elements that more often form the vertebrate mandible, such as the mentomeckelian bone. Although synapomorphic for ornithischians, the predentary does not seem neomorphic for the group, but primarily homologous to parts of the symphyseal region of the lower jaw of other vertebrates.

The sphenodontian fossil record in South America is well known from Mesozoic and Paleogene deposits of Argentinean Patagonia, mainly represented by opisthodontians, or taxa closely related to the modern Sphenodon. In contrast, the Brazilian fossil record is restricted to the Caturrita Formation, Late Triassic of Rio Grande do Sul, represented by several specimens of Clevosauridae, including Clevosaurus brasiliensis Bonaparte and Sues, 2006. Traditionally, Clevosauridae includes several Late Triassic to Early Jurassic taxa, such as Polysphenodon, Brachyrhinodon, and Clevosaurus, the latter well-represented by several species. The detailed description of the specimen MCN-PV 2852 allowed the first systematic revision of most Clevosaurus species. Within Clevosauridae, Polysphenodon is the most basal taxon, and an IterPCR analysis revealed Brachrhynodon as a possible Clevosaurus; C. petilus, C. wangi, and C. mcgilli as possibly distinct taxonomic entities; and the South African Clevosaurus sp. is not closely related to C. brasiliensis. These data indicate the need of a deep phylogenetic review of Clevosauridae, in order to discover synapomorphic characters among the diversity of these Triassic/Jurassic sphenodontians.

PLEISTOCENE RODENTS OF COASTAL PLAIN OF RIO GRANDE DO SUL STATE, BRAZIL. This work deals with the first Lujanian (late Pleistocene) record of the rodents Reithrodon auritus and Myocastor coypus for Rio Grande and Santa Vitoria do Palmar municipalities, and the first record of a Caviidae Dolichotinae-like and an Echimyidae for the Rio Grande do Sul State.

NEW MATERIAL OF CARNIVORA FROM THE PLEISTOCENE OF RIO GRANDE DO SUL STATE, BRAZIL. Carnivora materials coming from the Sistema Laguna-Barreira III, southern portion of the Coastal Plain of Rio Grande do Sul State, Late Pleistocene are decribed. New postcranial remains of Smilodon populator and Otaria byronia are presented. Isolated teeth of Dusicyon cf. D. avus and cf. Theriodictis represent the first Canidae record for this State.

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 …

The coastal plain of the state of Rio Grande do Sul, in southern Brazil, includes four barrier-lagoon depositional systems formed by successive Quaternary sea-level highstands that were correlated to marine isotope stages (MIS) 11, 9, 5 and 1, despite the scarcity of absolute ages. This study describes a sea-level highstand older than MIS 5, based on the stratigraphy, ages and fossils of the shallow marine facies found in coastal barrier (Barrier II). This facies outcrops along the banks of Chuí Creek, it is composed of fine, well-sorted quartz sand and contains ichnofossils Ophiomorpha nodosa and Rosselia sp., and molluscan shells. The sedimentary record indicates coastal aggradation followed by sea-level fall and progradation of the coastline. Thermoluminescence (TL) and electron spin resonance (ESR) ages from sediments and fossil shells point to an age of ∼220 ka for the end of this marine transgression, thus correlating it to MIS 7 (substage 7e). Altimetric data point to a maximum amplitude of about 10 meters above present-day mean sea-level, but tectonic processes may be involved. Paleoceanographic conditions at the time of the highstand and correlations with other deposits in the Brazilian coasts are also discussed. A planície costeira do estado do Rio Grande do Sul, no sul do Brasil, inclui quatro sistemas deposicionais do tipo laguna-barreira formados por sucessivas transgressões marinhas do Quaternário, correlacionadas aos estágios isotópicos marinhos (MIS) 11, 9, 5 e 1, apesar da escassez de idades absolutas. Este estudo descreve um máximo transgressivo marinho mais antigo que o MIS 5, com base na estratigrafia, datações e fósseis encontrados na fácies marinho raso de uma barreira costeira (Barreira II). Esta fácies encontra-se exposta ao longo das barrancas do Arroio Chuí, é composto por areia quartzosa fina, bem-selecionada, com icnofósseis Ophiomorpha nodosa e Rosselia sp., e conchas de moluscos. O registro sedimentar indica agradação da costa seguida por regressão do nível do mar e progradação da linha de costa. Datações por termoluminescencia (TL) e ressonância do spin do elétron (ESR) em sedimentos e conchas fósseis indicam uma idade de ∼220 ka para o final desta transgressão, correlacionando-a, portanto, ao MIS 7 (sub-estágio 7e). Dados altimétricos indicam amplitude máxima de aproximadamente 10 metros acima do nível atual do mar, mas processos tectônicos podem estar envolvidos. Condições paleoceanográficas à época da transgressão e correlações com outros depósitos da costa brasileira também são discutidos.

A primitive ‘ictidosaur’ from lower Norian beds of southern Brazil, Riograndia guaibensis gen. et sp. nov., represented by a fragmentary skull and a lower jaw bearing a complete dentition, shows a more generalized morphology than Chaliminia from the Upper Triassic of Argentina and PachygenelusDiarthrognathus from the Lower Jurassic of South Africa, Canada and Greenland. The frontal bone borders the orbit, and ventrally contacts the dorsal process of the palatine. The secondary bony palate extends back to the last postcanine. I1 and i2 are reduced, whereas I2-3 and i1 are hypertrophied. Both PC 1–7 and pc 1–7 have blade-like crowns without cingula and with 5–9 small sharp cuspules. The upper postcanine crowns are semicircular in labial view with the cuspules around their margins. The lower postcanine crowns are asymmetrical with most of the cuspules dorsodistally distributed. The possible origin of this peculiar dentition is interpreted as the retention of the juvenile dentition of ancestors. The hypothesis that Riograndia guaibensis and the so-called ‘ictidosaurs’ might have been derived from gomphodont cynodonts is presented.

A male specimen of Mirounga leonina Linnaeus, 1758 age estimated betvveen 7-8 years old, collected at Santa Vitória do Palmar, Rio Grande do Sul State, soutiiernmost Brazil (32º44'S and 53º22'W) is presented. Ali the skeleton was recovered except the rostral region. It shows an advanced osteomyelitis in the lefl dentary, extending from the synfisis until the middle portion of the body; as well as Scheuermann disease at lumbar vertebrae. Such diseases could explain its presence at that locality, where rt was shot. The bullct was recovered from the rostrum, and might be responsible for death. This is the first vhlually complete skeleton of M. leonina recovered from Brazilian coast.

The studied species were Arctocephalus australis (Zimmermann, 1783) and Arctocephalus tropicalis (Gray, 1872), (five specimens of each one). Anomalies were discussed under the light of theories which relate the ancestry of pinnipeds with the Ursidae; as well as concerning the evolutionary trends supposed for the Otariidae. Pathologies were related to alimentary and reproductive habits.

Bone diseases and tooth alterations in 47 specimens of Otaria byronia (Blainville, 1820), from southern Brazilian coast, were analized. Tooth wear and the associated bone pathologies were determined, as well as their percentuals. The main infection was osteomyelitis associated with tooth alterations, such as fractures and attrition, both of them exposing the pulp chamber. Tooth attrition increases with age, favoring fractures and their complications, including osteomyelitis, causing a high frequency of them in specimens presenting more pronounced tooth wear. In one specimen tuberculosis was found in the maxilla, perhaps primarily pulmonary. The high frequency of enamel hypoplasia might reflect cyclic food deficit. Infections and tooth fractures might be related to behaviour, such as fishermen interaction, territorial fighting, and accidents during food capture.