Biostratigraphy of Baghamshah Formation based on calcareous nannofossils in the Southwest Tabas, Iran

The Tabas Block is part of the Central Iran microcontinent, located between the Lut Block in the East and the Yazd Block in the West. The Baghamshah Formation is the second lithostratigraphic unit from the sedimentary cycle of the Magu Group and the Baghamshah Subgroup in the Jurassic of Tabas Block. This formation is conformably underlaid with the grey pisoidal limestones of the Parvadeh Formation and overlaid with the Pectinid limestones of the Kamar-e-Mehdi Formation (Esfandiar Subgroup). In this research, the biostratigraphy of the Baghamshah Formation in the Rizu and Kamar-e-Mehdi sections, based on calcareous nannofossils, is examined. The thickness of the Baghamshah Formation in the Rizu section is 270 m (mostly including marl and green shales with intercalation of limestones and calcareous sandstones), and in the Kamar-e- Mehdi section is 236 m (composed of gypsiferous marly shales, marl, marly shales and alternation of marl-shale with limestones and calcareous sandstones). According to the taxonomic studies in the Rizu section, 52 species belong to 24 genera, and in the Kamar-e-Mehdi section, 45 species belong to 23 genera of calcareous nannofossils. Based on index calcareous nannofossils, the CC1, CC2, CC3, and CC4 biozones established by Sissinghh in both sections were determined. It is mentioned that CC5 biozone only occur in Kamar-e-Mehdi section. According to the identified biozones, the suggested age of the Baghamshah Formation is early Berriasian–early Hauterivian in the Rizu section, and early Berriasian–late Hauterivian in the Kamar-e-Mehdi section. Keywords: biostratigraphy, Baghamshah, calcareous nannofossils,Tabas, Iran.

Upper Pleistocene–Holocene in the continental slope of the Cará Basin: an integrated analysis based on planktic foraminifera, sedimentological and geochemical aspects

This research addresses paleoclimatic variations using sedimentological, geochemical, and planktic foraminifera. The study was carried out in a survey core (ANP 1011) collected on the continental slope of the Icaraí Sub-basin (Ceará Basin), on the coast of the Municipality of Itapipoca, CE, Brazil. Particle size analysis, CaCO3 content, Ti/Ca and Fe/Ca ratios, and the analysis of foraminifera associations for biostratigraphic purposes were performed. Based on the relative abundance of planktic foraminifera, with indicators of warm and cold water throughout the studied cores, two biozones (Y: Upper Pleistocene and Z: Holocene), and two subzones (Z2 and Z1) were recognized. The data of sedimentological markers obtained confirmed the occurrence of more wet phases in northeastern Brazil during the early stages of the Holocene. The Ti/Ca and Fe/Ca ratios, as well as the geochemical and micropaleontological proxies, indicated a farther north displacement of the Intertropical Convergence Zone (ITCZ) in the Pleistocene–Holocene transition. This may have caused greater precipitation in the Northeastern region of Brazil, effectuating the entry of a high volume of terrestrial sediments directly into the ocean basin. Keywords: Quaternary biostratigraphy, marine sedimentation, ITCZ mobility, paleoclimate.

Palinologia de turfas do alto curso do Arroio Cará, Coxilha Rica, Santa Catarina, Brasil

Palynology of peaty sediments from the high course of Cará Brook Creek, Coxilha Rica, Santa Catarina, Brazil. This paper presents the results of the palynological study of a sedimentary core collected in a bog in the upper part valley of Cará Brook Creek, in the cultural territory of Coxilha Rica, located in the Campos Gerais Plateau in Santa Catarina, Southern Brazil. The base of the core was dated in 6.900 14C years BP (7,845–7,690 cal years BP). The identification of the palynomorphs and the cluster analysis made possible to define two distinct palynological phases, despite the predominance of grassland vegetation throughout the whole core. From 34 cm, the frequency of bryophytes decreases, accompanied by the increase of the diversity of all vegetal taxa. Throughout the core, the most frequent families are Poaceae, Cyperaceae Apiaceae. The results indicate that the landscape of the upper course of the Brook Creek was characterized by grasslands from 6,900 14C years BP under a regional and humid climate, with a temperature increase in the historical period. Keywords: Middle Holocene, palynomorphs, grasslands, Araucaria forest, Highland.

The paleoecology of Pleistocene giant megatheriid sloths: stable isotopes (δ13C, δ18O) of co-occurring Megatherium and Eremotherium from southern Brazil

The Pampa in subtropical Brazil (State of Rio Grande do Sul) is the only area of South America known so far where fossils of the Pleistocene giant megatheriid sloths Megatherium americanum, characteristic of subtropical-temperate areas, and Eremotherium laurillardi, widespread in the tropical zone, were discovered in the same deposits (Pessegueiro Creek and Chuí Creek), but it is not clear whether this co-occurrence is a product of taphonomic mixture, or co-existence, which would imply niche partitioning. In order to understand their paleoecology and reconstruct the associated paleoenvironments, dentin samples of both megatheriids from the two sites were analyzed for their carbon (δ13C) and oxygen (δ18O) isotope ratios. The δ13C values of Megatherium indicate mixed diet of C3-C4 plants with higher content of the latter in Pessegueiro Creek, whereas the δ13C values of Eremotherium indicate C3-dominated diets, the more negative value in Pessegueiro Creek possibly related to the canopy effect. The δ18O of Eremotherium points to 18O-depleted water sources, possibly also influenced by the diet, whereas Megatherium ingested 18O-enriched water. The results show that co-existence of both megatheriids would have been ecologically possible, and that the Pampa was occupied by open grasslands/woodlands, with closed forests in Pessegueiro Creek. The δ13C of Eremotherium from intertropical Brazil indicate a more generalist habit than Megatherium from subtropical Brazil and Argentina, which probably facilitated its dispersion from the tropics up to subtropical areas along two different routes, one along the coastal plain, and the other along the Paraná River Basin across central South America, following the southward expansion of riparian forests during warmer stages. The reduction of those forests during intervening cold stages possibly led to its disappearance in southern Brazil. Keywords: Quaternary, paleobiogeography, stable isotopes, Pampa, coastal plain, megafauna.

Gastropods from the Solimões Formation (upper Miocene), Acre Basin, Brazil

A taxonomic review of Miocene gastropods from the Solimões Formation, Acre Basin, Brazil, from specimens collected at Cachoeira do Bandeira, Oriente, and an outcrop named Spot 04, is here presented. Three ampullariid species (Pomacea maculata, P.planorbula, Pomacea sp.), one thiarid species (Aylacostoma sp.), and one cochliopid species (Sioliella sp.) are identified for these deposits. These gastropod are known to occur in freshwaters environments, thus consolidating the hypothesis of a non-influence of brackish water on the upper Miocene deposits of the Acre Basin. The previous identification of P. maculata and Aylacostoma sp. is changed here considering biometrical analyses and shell morphological descriptions. The first report of Sioliella in this basin increases the gastropod fauna known for these strata and expands the range of this genus. Keywords: Pomacea, Aylacostoma, Sioliella, Ampullariidae, Thiaridae, Cochliopidae.

Mesosaur taxonomy reappraisal: are Stereosternum and Brazilosaurus valid taxa?

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 accepted 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 Paraná 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.

New Cingulata (Mammalia, Xenarthra) from the Upper Lumbrera Formation (Bartonian, middle Eocene), Salta Province, Argentina

We describe isolated remains of a Paleogene cingulate from El Simbolar locality, Upper Lumbrera Formation (Bartonian), southern Salta Province, northwestern Argentina. The material consists of numerous fixed, movable, and caudal sheath osteoderms. The specimen has large-sized osteoderms, with a lageniform main figure, as in Utaetus buccatus, U. laxus, U. argos, ?U. deustus, Punatherium catamarcensis, and the basal euphractin Archaeutatus. The combination of morphological characters, in addition to its large size, allows us to recognize a new species of “Utaetini” for the Paleogene of northwestern Argentina. This new species of ?Utaetus represents the oldest record of Euphractinae in this region, and strengthens the endemic condition of its Paleogene faunas. Keywords: Cingulata, osteoderms, El Simbolar, Paleogene, Salta, Argentina.

A incomum associação de peixes e caranguejos da Formação Romualdo, Aptiano-Albiano da Bacia sedimentar do Araripe, NE do Brasil

The unusual association of fish and crabs from Romualdo Formation, Aptian–Albian of the Araripe sedimentary Basin, NE Brazil. In a study and collection of fossils from the Romualdo Formation in “Araripe pernambucano”, an association of Vinctifer comptoni and Rhacolepis buccalis with eubrachyurans and orithopsids crabs was observed in four calcareous nodules. Associations were discussed based on ecological and taphonomic hypotheses. It is noted from the degree of articulation of the organisms, that either the death or the availability of crab moults in the sediment possibly occurred before the death of the fish. In addition, the fish do not have teething consistent with feeding on crabs. Thus, this association would occur due to fossilization processes and not due to ecological interactions. The study also emphasized systematic and paleogeographic aspects of the groups. Romualdocarcinus salesi is probably related to the “higher” true crabs (Eubrachyura), a hypothesis already raised in previous works, due to the preservation of its dorsal carapace next to a pleon of subquadrangular shape similar to those seen in this group. The occurrence of Exucarcinus gonzagai associated with fish, in concretions in the shales, can raise the question of E. gonzagai and Araripecarcinus ferreirai species as synonyms. The data obtained with the survey of the paleogeographic distribution of fish and crabs in geological formations of correlated age corroborates the hypothesis of the Tethyan marine influence in Araripe. Keywords: ichthyolites, decapods, paleoecology, taphonomy, Santana Group, Cretaceous.

Evolution of the Semideciduous-Riparian Forest (ecotone Cerrado-Atlantic Forest) during the late Holocene, Southeast of Brazil

The floodplains of meandering rivers in southeastern Brazil represent places where the sedimentary record associated with the history of transition/ecotone areas and exchange of biomes accumulates, such as the Cerrado (Cerradão Forest) and Atlantic Forest (Semideciduous-Riparian Forest). The present study aims to use palynological, isotopic (δ13C, δ15N and 14C), and anthracological indicators in cores taken from three abandoned meander bends to make inferences about environmental evolution, vegetation reconstruction, and climatic inferences. The study area is located in the Mogi Guaçu River Basin, in the countryside of São Paulo State. The studies show that ~2,730 BP (stage I), the area underwent through a more humid climatic phase compared to the current one, which allowed the expansion of the Riparian Semideciduous Forest. After that date, in stage II (1,800 to 510 BP), the percentage of the Cerrado (Cerradão Forest) increased, due to a drier period. From 510 BP to the present day (stage III), humidity has taken place with a new expansion of the Riparian Semideciduous Forest, although elements of Cerrado are present. Microscopic charcoal fragments were found in all stages and may infer the incidence of paleo-wildfires during the Late Holocene. The results indicate that both phytophysiognomies remained for the studied period, varying their expansion depending on the humidity present in each stage. Although lakes formed by abandoned meanders are not areas with the best palynological record, they are frequent environments in the interior of the continents. If properly interpreted, they may provide relevant information to vegetation and climatic changes for the areas. Keywords: paleoenvironmental studies, Holocene, river dynamics, pollen grains, isotopic analysis, charcoal fragments.

First occurrence of the giant shark Carcharocles megalodon (Agassiz, 1843) (Lamniformes; Otodontidae) at Buenos Aires Province, Argentina

Carcharocles megalodon is considered a macropredatory shark that inhabited the seas around the world from middle Miocene to late Pliocene. In Argentina, it has only been formally recorded at two localities. Here, we report the first record for this taxon in the Buenos Aires Province. This occurrence is based on an isolated tooth recovered on the beach at the Punta Médanos locality, which lacks clear stratigraphic context. Based on the regional geology, the specimen probably came from Pliocene beds. Its size indicates that it probably belongs to a juvenile individual. Keywords: Carcharocles megalodon, macropredatory shark, fossil teeth, Mar de Ajó.