Scielo RSS <![CDATA[Anais da Academia Brasileira de Ciências]]> vol. 91 num. lang. en <![CDATA[SciELO Logo]]> <![CDATA[Distributional patterns of Aptian-Albian paleoichthyofauna of Brazil and Africa based on Track Analysis]]> ABSTRACT The Aptian-Albian paleoichthyofauna in Brazil and Africa is quite diverse, yet their geographic patterns still require accounts. This work consists of a panbiogeographical analysis of paleoichthyofauna from Aptian-Albian through track analysis. Geographic coordinates were obtained and converted into paleocoordinates. Individual Tracks (ITs) and Generalized Tracks (GTs) were built with the aid of ArcView GIS v3.2 program using Trazos2004 extension. As a result, four GTs and tree Biogeographic Nodes (A, B and C) had been identified. GTs 1 and 2 shows two different faunas. GT3 indicates similarity between Brazil and Africa paleoichthyofauna suggesting the break-up of Gondwana as the event that separated it. GT4 represents a probable local seaway produced by transgressions. In the Node A a unique fauna was found indicating the presence of a third biota with its own characteristics. Node B is associated with the break-up of the supercontinent Gondwana. Node C was related to fauna exchange promoted by marine ingression and epicontinental seas that occurred during Aptian-Albian. We concluded that there is a relationship between the distributional patterns of biota and events such as the break-up of Gondwana, the formation of Atlantic Ocean and eustatic movements that affected South America and Africa. <![CDATA[Holocene history of a lake filling and vegetation dynamics of the Serra Sul dos Carajás, southeast Amazonia]]> ABSTRACT Down-core changes in sedimentary facies, elemental geochemistry, pollen, spore, δ13C, δ15N and radiocarbon records from a filled lake, named R4, of the Serra Sul dos Carajás were used to study the relationship between the paleomorphological and paleoecological processes and their significance for Holocene paleoclimatology of the southeast Amazonia. The sediment deposition of the R4 lake started around 9500 cal yr BP. Increase of detrital components from 9500 to 7000 cal yr BP suggests high weathering of surrounding catchment rocks and soils, and deposition into the lake basin under mudflows. At that time, montane savanna and forest formation were already established suggesting predominance of wet climate. However, from 7000 to 3000 cal yr BP, a decline of detrital input occurred. Also, forest formation and pteridophytes were declined, while palms and macrophytes were remained relatively stable, indicating that water levels of the lake is likely dropped allowing the development of plants adapted to subaerial condition under drier climate conditions. After 3000 cal yr BP, eutrophication and low accommodation space lead to high lake productivity and the final stage of the lake filling respectively, and forest formation may has acquired its current structure, which suggests return of wetter climate conditions. <![CDATA[A new saurolophine hadrosaurid (Dinosauria: Ornithopoda) from the Upper Cretaceous of Shandong, China]]> ABSTRACT A new saurolophine hadrosaurid, Laiyangosaurus youngi gen. et sp. nov. is described and phylogenetically analyzed based on several cranial elements from the Jingangkou Formation, Wangshi Group, Upper Cretaceous of Laiyang, Shandong, China. Laiyangosaurus youngi differs from other members of the saurolophine clade on the basis of a number of autapomorphies, including a prominent and narrow ridge on the lateral side of the nasal which forms the posterodorsal and posterior margin of the circumnasal depression, a primary ridge that runs along most of the maxillary tooth row that is slightly deflected posteriorly, a retroarticular process of the surangular that is dorsolateroposteriorlly recurved, and orbital margins that are wider than the infratemporal margins of the jugal. This new taxon can be further distinguished by a number of unique combination of characters, including dorsal margin of nasal is flat, absence supracranial crest, a relatively shallow and rostrodorsally directed caudal margin of the lacrimal process of the jugal, and one or more foramina present on the rostral surface of the premaxilla. A phylogenetic analysis indicates that L. youngi comprises a monophyletic clade, which is known as Edmontosaurini. <![CDATA[New Crocodyliform specimens from Recôncavo-Tucano Basin (Early Cretaceous) of Bahia, Brazil]]> ABSTRACT In 1940, L.I. Price and A. Oliveira recovered four crocodyliform specimens from the Early Cretaceous Bahia Supergroup (Recôncavo-Tucano Basin). In the present work, we describe four different fossil specimens: an osteoderm, a fibula, a tibia, and some autopodial bones. No further identification besides Mesoeucrocodylia was made due to their fragmentary nature and the reduced number of recognized synapomorphies for more inclusive clades. With exception of the fibula, all other specimens have at least one particular feature, which with new specimens could represent new species. The new specimens described here increase the known diversity of Early Cretaceous crocodyliforms from Brazil. This work highlights the great fossiliferous potential of Recôncavo-Tucano Basin with regard to crocodyliform remains. <![CDATA[A review of the Quaternary Scelidotheriinae (Mammalia, Xenarthra, Tardigrada) from the Tarija-Padcaya basin, Bolivia]]> ABSTRACT The Mylodontidae Scelidotheriinae (Mammalia, Xenarthra, Tardigrada) are a diversified clade of South American fossil ground sloths, with a wide geographic distribution, especially in high and middle latitudes. According to the last revision, the Quaternary diversity includes the genera Scelidotherium, Catonyx, and Valgipes. The clade Scelidotheriinae is well represented in the Pleistocene of the Tarija-Padcaya basin, and the first mention of these ground sloths correspond to the middle of the XIX Century. Since then, several species (i.e., Scelidotherium tarijensis, Scelidodon tarijensis, Scelidotherium capellini) have been reported as inhabiting the Tarija-Padcaya basin during the Pleistocene. Despite the abundance of fossil records of Scelidotheriinae in this area, no modern taxonomic revisions are available. In consequence, in this contribution a revision of the remains assigned to Scelidotheriinae from the Tarija-Padcaya basin is accomplished, and some biostratigraphic and geographic implications are discussed. Our results show that one single species (Catonyx tarijensis) can be recognized in the studied area, whereas a supposed smaller one (Scelidotherium patrium) actually corresponds to juvenile specimens of C. tarijensis. <![CDATA[<em>Baalsaurus mansillai</em> gen. et sp. nov. a new titanosaurian sauropod (Late Cretaceous) from Neuquén, Patagonia, Argentina]]> Abstract We describe a dentary of a new titanosaur sauropod, Baalsaurus mansillai, gen. et sp. nov. from the Late Cretaceous of Patagonia, Argentina. The material comes from the Portezuelo Formation, Neuquén Group. Titanosaur sauropods lower jaws are scarce and only nine taxa with dentaries have been described. There are two types of morphology in titanosaur dentaries; “L” shaped or “U” shaped based on the shape, without a phylogenetic issue. In this paper; we recognize a new taxa, Baalsaurus mansillai, represented by an “L” shaped dentary with three apomorphic characters that are not present in other taxa: dentary alveoli with 10 teeth in the anterior ramus, a ventrally and anteriorly inclined symphysis and a wide ventral Meckelian groove surrounded by a thin lamina that forms a keel on the ventral border of the dentary. <![CDATA[A new protodidelphid (Mammalia, Marsupialia, Didelphimorphia) from the Itaboraí Basin and its implications for the evolution of the Protodidelphidae]]> Abstract The Protodidelphidae was a group of marsupials that lived in Gondwana from the early to middle Eocene. Among South American faunas, the Itaboraí Basin calls attention by the presence of four genera and six species. Herein is described Bergqvistherium primigenia gen. et sp. nov., a new protodidelphid from the Itaboraí Basin - lower Eocene. This taxon differs from other protodidelphids in the smaller size, developed entocristid, less brachyo-bunoid adaptations, and entoconid more mesial than the hypoconid. These characters are recovered as plesiomorphies of the Protodidelphidae, supporting Bergqvistherium as an early-divergent lineage of this group. The Protodidelphidae fauna of the Itaboraí Basin is represented by less specialized “basal” taxa, such as Bergqvistherium and Periprotodidelphis; and more specialized apical taxa, such as Guggenheimia, Protodidelphis, and Carolocoutoia. This result indicates that the diversification of apical protodidelphids probably was a result of a relatively short-time event, occurring during the early Eocene. This evolutionary event can be directly correlated to the increase in the temperatures and the extension of tropical forests resulted by the Paleocene-Eocene Thermal Maximum during the Itaboraiense time span. The study supported a Late Cretaceous origin for the Protodidelphidae, which agrees with molecular studies for the Didelphimorphia.