Enamel dentition microstructure of Mariliasuchus amarali (Crocodyliformes, Notosuchia), from the Upper Cretaceous (Turonian–Santonian) of the Bauru Basin, Brazil

SummaryBlind snakes (Scolecophidia) are minute cryptic snakes that diverged at the base of the evolutionary radiation of modern snakes. They have a scant fossil record, which dates back to the Upper Paleocene-Lower Eocene (∼56 Ma); this late appearance conflicts with molecular evidence, which suggests a much older origin for the group (during the Mesozoic: 160–125 Ma). Here we report a typhlopoid blind snake from the Late Cretaceous of Brazil, Boipeba tayasuensis gen. et sp. nov, which extends the scolecophidian fossil record into the Mesozoic and reduces the fossil gap predicted by molecular data. The new species is estimated to have been over 1 m long, much larger than typical modern scolecophidians (<30 cm). This finding sheds light on the early evolution of blind snakes, supports the hypothesis of a Gondwanan origin for the Typhlopoidea, and indicates that early scolecophidians had large body size, and only later underwent miniaturization.

The Bauru Basin (south-central Brazil) fossils have largely contributed to understand the faunal composition of South American Cretaceous. Among those, several turtle specimens were retrieved from those deposits, all belonging to Podocnemidoidae, the single group known from the Basin. On the other hand, only incomplete shell elements indicate large turtles such as ‘Peirópolis A’. Another shell fragment, a large peripheral plate from the Marília Formation, is described here. Its lack of surface ornamentation, and deep sulci are generally typical for podocnemidoids. The plate exhibits a narrow knob slightly projected onto the pleuro-marginal sulcus, absent in any other Bauru Basin turtle. According to extant and fossil podocnemidoids measures, we estimated this individual reached 1 m of carapace length, exceeding in size all other taxa known from the Basin. This new report reveals a broader size variation among podocnemidoids from the Late Cretaceous of Bauru Basin and a morphological diversity previously unknown for the period, comparable to those of the Amazon Basin today, in which inhabits the largest extant podocnemidoid Podocnemis expansa. Furthermore, the occurrence of such large turtles implies the presence of perennial streams on the northeastern portion of the Bauru Basin during the Maastrichtian and a richer environment than previously thought.

The first bony theropod record from the Campanian Uberaba Formation (Bauru Group) is described. It consists of an isolated caudal centrum (CPPLIP 1324) found in the city of Uberaba, Minas Gerais State, Brazil. The amphicoelous centrum possesses a length to height ratio of 1.74, deep elliptical lateral pneumatic foramen representing 26% of centrum length with three main sub-circular air chambers, andcamellate internal structure.This combination of features is shared with Aerosteon, Megaraptor, and Orkoraptor from the Late Cretaceous of Argentinaand with the Megaraptora indet. fromthe São José do Rio Preto Formation (Bauru Group), São Paulo State,allowing us to refer it to the Megaraptora clade (Tetanurae, Neovenatoridae). As such, the new specimen represents the second megaraptoran from the Late Cretaceous of Brazil and provides new information on tail anatomy on this bizarre group.

A new fossil frog (Lissamphibia: Anura) from the Late Cretaceous of Brazil and the early evolution of neobatrachians

A bone to pick: stable isotope compositions as tracers of food sources and paleoecology for notosuchians in the Brazilian Upper Cretaceous Bauru Group

Theropod teeth from the Adamantina Formation (Bauru Group, Upper Cretaceous), Monte Alto, São Paulo, Brazil

The Upper Cretaceous Bauru Group deposits furnished several species of Crocodylomorpha, especially notosuchians. However, little is known about the feeding habits of this diverse group of crocodylomorphs. The dental histology is a destructive approach that can provide important information on tooth growth and feeding habits of fossil vertebrates. So far, few studies dealt with crocodylomorph dental histology and the ones available mainly focused on fossil and living neosuchians. In this work, we analyse the dental histology of three notosuchians commonly found in the Upper Cretaceous rocks of the Bauru Group: juvenile and adult Baurusuchidae, a large Sphagesauridae, and Mariliasuchus amarali. Our analyses indicate that tooth formation varied in these three taxa. In Mariliasuchus, a tooth took less than 2 months to be completely grown. On the other hand, in Sphagesauridae and Baurusuchidae, the tooth formation could take about 6 months to be completed. Mariliasuchus and Sphagesauridae have proportionally thicker enamel in comparison to Baurusuchidae. Additionally, the enamel thickness and its substantial development in the chewing area in Sphagesauridae indicate that apical advanced notosuchians are more adapted to process food items than more basal forms like Mariliasuchus.

The record of theropod dinosaurs in Brazil is very scarce. One of the most promising lithostratigraphic units for those reptiles is the Bauru Group. The dinosaur remains found in this unit are mainly those of sauropods, while theropods are represented mostly by teeth. Here we describe a right scapula (housed at the Earth Science Museum of the Departamento Nacional de Producao Mineral/Rio de Janeiro) that is the first theropod scapula reported from the Cretaceous of Brazil and only the second osteological evidence of the Tetanurae from the Bauru Group. The specimen was recovered from the outskirts of Peiropolis, in Minas Gerais State. Comparisons with other theropod dinosaurs are limited, but the overall morphology of the new specimen indicates that it is neither a member of the Abelisauridae nor a member of the Avialae. It also differs from more basal members of the Theropoda, but its overall shape is consistent with several derived members of the Tetanurae, likely a non-avialan maniraptoran. Despite the lack of precision in its taxonomic position, the new specimen confirms the presence of non-avialan Maniraptora in the Bauru Group.

Tetrapods from the Upper Cretaceous (Turonian–Maastrichtian) Bauru Group of Brazil: a reappraisal

The Cretaceous Kem Kem beds of Morocco and equivalent beds in Algeria have produced a rich fossil assemblage, yielding, amongst others, isolated sauropod teeth, which can be used in species diversity studies. These Albian-Cenomanian (∼113–93.9 Ma) strata rarely yield sauropod body fossils, therefore, isolated teeth can help to elucidate the faunal assemblages from North Africa, and their relations with those of contemporaneous beds and geographically close assemblages. Eighteen isolated sauropod teeth from three localities (Erfoud and Taouz, Morocco, and Algeria) are studied here, to assess whether the teeth can be ascribed to a specific clade, and whether different tooth morphotypes can be found in the samples. Two general morphotypes are found, based on enamel wrinkling and general tooth morphology. Morphotype I, with mainly rugose enamel wrinkling, pronounced carinae, lemon-shaped to (sub)cylindrical cross-section and mesiodistal tapering towards an apical tip, shows affinities to titanosauriforms and titanosaurs. Morphotype II, characterized by more smooth enamel, cylindrical cross-section, rectangular teeth with no apical tapering and both labial and lingual wear facets, shows similarities to rebbachisaurids. Moreover, similarities are found between these northwest African tooth morphotypes, and tooth morphotypes from titanosaurs and rebbachisaurids from both contemporaneous finds from north and central Africa, as well as from the latest Cretaceous (Campanian–Maastrichtian, 83.6 Ma–66.0 Ma) of the Ibero-Armorican Island. These results support previous hypotheses from earlier studies on faunal exchange and continental connections between North Africa and Southern Europe in the Cretaceous.

Bauru Basin (Upper Cretaceous) spans 190,000 km² in western segment, Mato Grosso do Sul and Goiás states, Brazil. The Supersequence is a predominantly sandy siliciclastic unit. In Mato Grosso do Sul state a substantial portion of the sedimentary supersequence was considered indivisible. This research, based on regional field surveys, presents updates to the geological map, depositional model, and lithostratigraphic chart of the western Bauru Basin. In Mato Grosso do Sul, the Rio Paraná Formation was identified, directly overlaying the Serra Geral Group in the south/southwest, and the Botucatu Formation on north/central region. The Santo Anastácio Formation outcrop area was found to be smaller than previously mapped, showing lateral contacts with the Rio Paraná and Vale do Rio do Peixe formations. The Vale do Rio do Peixe Formation, conversely, now exhibits a larger mapped area. Additionally, the Marília Formation were discovered in São Gabriel do Oeste-MS, previously marked as detrital-lateritic cover.

Carcharodontosauridae theropod tooth crowns from the Upper Cretaceous (Bauru Basin) of Brazil: A reassessment of isolated elements and its implications to palaeobiogeography of the group

This paper aimed at characterizing the sandstones and paleosols of the Marília Formation (Bauru Basin - upper Cretaceous), present in the southern region of Goiás and in the region of Marília (northwestern São Paulo), by means of petrographic analyses and field studies. Facies and architectural elements, compositional analyses of conglomerates and petrographic analyses of sandstones and paleosols were carried out, thus defining, and interpreting the depositional mechanisms. The Formação Marília, in the southern region of Goiás, is interpreted as an extensive eolic sand sheet, cut by ephemeral rivers, in which cyclic alternation between eolic deposits and paleosols occurs. The construction of the lithosomes was determined by different paleoclimatic conditions, responsible for moments with higher water availability, which favored the formation of soils, and others with lower water availability, favorable to the sedimentation of sandy deposits with eolian undulating marks. Three architectural elements were recognized: paleosols, sandy sheet deposits dominated by eolian wavy marks, and ephemeral river deposits. Paleosols are the most frequent elements and consist prevalently of Aridissols and subordinately of Alphissols. The sandstones were classified into lithoarenites (predominantly), sublithoarenites and feldspathic lithoarenites. The Marília Formation, in the Marília region, shows different development conditions in the lower and upper part of the Serra de Echaporã: in the lower part eolian sandstone deposits and ephemeral lakes alternate with paleosols indicating high water table and in the upper part eolian deposits and paleosols of arid and semiarid climate occur. Three architectural elements were recognized: paleosols, sand sheet deposits dominated by eolian wavy marks, and playa lake deposits. The paleosols consisted prevalently of Aridissols and subordinately of a gleying paleosol type. No ephemeral fluvial deposits were found. The sandstones were classified into sublithoarenites and subarcosites (predominantly). A construction model was proposed for this former sand sheet. The construction phase was characterized by sediment input by rivers during a wetter period (first input), and by several cycles of erosion of ephemeral river deposits and soils during drier climatic phases (second input).

Paleoenvironmental and paleoclimatic reconstruction of Lower to Upper Cretaceous sequences of the Bauru Basin based on paleosol geochemistry and mineralogical analyses

A microvertebrate assemblage from the Adamantina Formation (Bauru Group, Upper Cretaceous) in São Paulo State, Brazil