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Protolipterna ellipsodontoides is a small bunodont South American native ungulate, generally considered an early litoptern, exclusively found in the Palaeogene Itaboraí Basin. Its dentition is well known; however, its mandibular morphology was only known by fragmentary materials. Here, we describe the first complete mandible of this species. A micro-CT scan reveals the first case of alveolus resorption in this putative early litoptern. Two accessory canals on the retromolar region are also described. Canals on the retromolar region are documented for other mammalian orders; however, this represents the first description of this feature for the Protolipternidae. Unlike more advanced litopterns, this species lacks specialisations related to strict herbivory, and its dental and mandibular morphology suggests an omnivore habit. A comparison with the mandible of another Itaboraian protolipternid, Miguelsoria parayirunhor, indicates the presence of different dietary specialisations. Body mass estimations for both species are also provided. [ABSTRACT FROM AUTHOR]

The Itaboraí Basin, municipality of Itaboraí, Rio de Janeiro, Brazil, preserved an early Eocene vertebrate assemblage. Among its representatives, Metatheria comprises its most diverse clade, with at least 29 genera and 43 species. Among large- to very large-sized taxa, protodidelphids are represented by Protodidelphis vanzolinii , P. mastodontoides , and Carolocoutoia ferigoloi. Protodidelphis mastodontoides was initially considered a different genus, Robertbutleria ; however, the synonymy of Robertbutleria with Protodidelphis has never been tested. A phylogenetic analysis recovered Robertbutleria as the sister taxon of Carolocoutoia and not Protodidelphis. Robertbutleria and Carolocoutoia share the presence of rounded upper molars, evident bunodonty, rounded postmetacrista, U-shaped protocone, asymmetric placement of m4, obliquely oriented p1-3, and absence of diastemata. The analysis recovered that the dental features considered for the synonymy of Robertbutleria with Protodidelphis represented plesiomorphies for Protodidelphidae (e.g., sinuous crest between StB and StD, marked increase in the size of the molars from M/m1 to M/m3). Based on the results, an emended diagnosis of Protodidelphinae (the clade that includes Protodidelphis , Robertbutleria , and Carolocoutoia) is presented. Two principal component analyses (PCAs) recognized protodidelphine taxa in different morphospaces, indicating differential allometric and morphofunctional patterns. Protodidelphis was a generalized frugivore, Robertbutleria was a fibrous frugivore, and Carolocoutoia was a turgent frugivore. Moreover, the similar morphological and morphofunctional indexes of protodidelphines suggest a "short time" evolutionary diversification for this clade, and that trophic specializations do not necessarily require great morphological changes, allowing the sympatric co-existence of morphologically similar ingroup genera. • Robertbutleria Marshall, 1987 is rescued as a valid genus of Protodidelphidae. • Robertbutleria was more closely related to Carolocoutoia than to Protodidelphis. • An emended diagnosis of Protodidelphinae (the clade that included Protodidelphis , Robertbutleria , and Carolocoutoia) is presented. • Itaboraí's protodidelphines explored differential frugivorous trophic niches. • Robertbutleria displays several features indicative of a potential fibrous frugivorous diet. [ABSTRACT FROM AUTHOR]

The Itaboraí Basin, located in Itaboraí, Rio de Janeiro, Brazil, has preserved one of the most important early Eocene vertebrate assemblages of the Southern Hemisphere. Among its representatives, Metatheria comprises its most diverse group, with a minimum of 29 genera and 43 species. Considering this diversity, tiny and very small taxa are represented by Jaskhadelphyidae and closely related taxa, "Peradectoidea", Sternbergiidae, Derorhynchidae, and an undescribed taxon with uncertain affinities, previously referred to as "cf. Armintodelphys ". Here, this last taxon is named Thylacopygmaeus oliveirai gen. et sp. nov.; it is distinguished by its extremely small size (inferred body mass less than 15 g) and in that its lower molars show the metaconid placed distally to the protoconid and a developed postentocristid. Two PCA analyses of T. oliveirai and other tiny-sized taxa from Itaboraí indicate that the new taxon exhibits distinctive morphometric and morphofunctional patterns compared to other sympatric tiny-sized taxa. The inclusion of T. oliveirai gen. et sp. nov. in a phylogenetic analysis recovered it as the sister taxon of Rumiodon , an early Oligocene herpetotheriid from Peru, based on the presence of a labiolingually compressed metaconid on m3 and a labiolingually compressed protoconid on m4. We group these two taxa within the Herpetotheriidae in a new clade, the Rumiodontinae nov. Contrary to a previous hypothesis, Thylacopygmaeus is not closely related to Armintodelphys. The results confirm the Paleogene occurrence of Herpetotheriidae in South America. • A new metatherian from the Itaboraí Basin, Thylacopygmaeus oliveirai gen. et sp. nov., is described. • Thylacopygmaeus oliveirai was a generalized insectivore and one of the smallest metatherians currently known. • A new clade is proposed for Herpetotheriidae, Rumiodontinae nov., to include Thylacopygmaeus oliveirai and Rumiodon from Peru. • Herpetotheriidae occurred during the Paleogene in South America from the early Eocene to the early Oligocene. [ABSTRACT FROM AUTHOR]

Although metatherians are known since Early Cretaceous, there is little evidence of bone lesions in this extremely diverse mammalian clade. Here, we report an asymptomatic and benign condition named torus mandibularis in an incomplete right dentary assigned to Patene simpsoni, a basal sparassodont from the early Eocene of São José de Itaboraí Basin, Brazil. This report represents the oldest evidence of bone lesion in a Metatheria, as well as the first occurrence of torus mandibularis in a nonhuman fossil. The proposed diagnosis was based on location and external appearance of the bone overgrowth. [ABSTRACT FROM AUTHOR]

Zeusdelphys complicatus is one of the most enigmatic metatherians from the Itaboraí Basin. The type and only known specimen was previously regarded as the upper dentition of Eobrasilia; an M4 of a new taxon; an M3 of a Kollpaniidae (now regarded as a group of “condylarths”); a probable M1 of an incertae sedis taxon; and as an M1 of a Protodidelphidae. Herein, we present a morphological review of the dental structures of Zeusdelphys complicatus, presenting new interpretations and comparing it with other North and South American taxa. We also perform a phylogenetic analysis in order to test the affinities of Zeusdelphys and the validity of most studied characters. The results recovered Zeusdelphys complicatus as more closely related to Hatcheritherium alpha than to any other metatherian. Glasbiidae were recovered as the sister lineage of Protodidelphidae within Didelphimorphia, as true marsupials. Ectocentrocristus was recovered as the sister taxon of Zeusdelphys + Hatcheritherium, as a Hatcheriformes. The analysis recovered this suborder as an independent lineage from Polydolopimorphia, being more closely related to “Alphadontidae”. The affinities with Protodidelphidae are a result of convergent evolution, as Zeusdelphys is more closely related to Hatcheritherium alpha from the Late Cretaceous of North America. The results support a North American origin for Hatcheriformes. The presence of strong sea-level lowstands and islands in the Caribbean Plate during the Late Cretaceous provide valid data to support a faunal interchange between Americas during the latest Late Cretaceous. Based on the results, Zeusdelphys represents a South American early Eocene surviving Hatcheriformes.

Zeusdelphys complicatus is one of the most enigmatic metatherians from the Itaboraí Basin. The type and only known specimen was previously regarded as the upper dentition of Eobrasilia; an M4 of a new taxon; an M3 of a Kollpaniidae (now regarded as a group of "condylarths"); a probable M1 of an incertae sedis taxon; and as an M1 of a Protodidelphidae. Herein, we present a morphological review of the dental structures of Zeusdelphys complicatus, presenting new interpretations and comparing it with other North and South American taxa. We also perform a phylogenetic analysis in order to test the affinities of Zeusdelphys and the validity of most studied characters. The results recovered Zeusdelphys complicatus as more closely related to Hatcheritherium alpha than to any other metatherian. Glasbiidae were recovered as the sister lineage of Protodidelphidae within Didelphimorphia, as true marsupials. Ectocentrocristus was recovered as the sister taxon of Zeusdelphys + Hatcheritherium, as a Hatcheriformes. The analysis recovered this suborder as an independent lineage from Polydolopimorphia, being more closely related to "Alphadontidae". The affinities with Protodidelphidae are a result of convergent evolution, as Zeusdelphys is more closely related to Hatcheritherium alpha from the Late Cretaceous of North America. The results support a North American origin for Hatcheriformes. The presence of strong sea-level lowstands and islands in the Caribbean Plate during the Late Cretaceous provide valid data to support a faunal interchange between Americas during the latest Late Cretaceous. Based on the results, Zeusdelphys represents a South American early Eocene surviving Hatcheriformes. [ABSTRACT FROM AUTHOR]

Since the discovery of the massive South Atlantic hydrocarbon reservoirs (Pre-Salt), the interest in these terrestrial carbonates has increased. In Brazil few examples of continental carbonates are known, and solely the occurrence described in this study can be recognized as continental thermal carbonate or travertine. The occurrence is part of the sedimentary sequence of the Itaboraí Formation, deposited in Itaboraí Basin, located in Rio de Janeiro state, about 60 km from the city of Rio de Janeiro. The basin dates back to the Paleocene due to its vertebrate fossil content, which can be found in a small half-graben basin (1.5 km × 0.5 km). Despite the small size of the basin, it represents a huge source of geological information for its diverse fossil assemblage, the occurrence of travertine and the exposition of alkaline dyke. Most of the studies regarding the basin are related to the extensive fossil community from the lake-fill facies succession, which are not directly related to the travertine deposition. The present study conducted a sedimentological investigation applying petrography, facies association and isotope analysis as its methodology. As a result, four distinct facies associations were described: Thermal Springs, Alluvial, Palustrine/Lacustrine and Fissural. Sedimentation succession allowed the study to recognize sedimentation and tectonic relationship. The origin of the thermal activity is probably related to the tectonic pulses of the hemi-graben system, so in these conditions two different contexts for travertine deposition associated to the flexural and active borders of the basin were established. The petrography exhibited shrubs textures with remarking crystalline quality indicating a major abiotic influence during the process of precipitation. The stable isotope ratios provided contrasting results against those expected for a thermal carbonate signature, but not so different from those expected for meteoric carbonate signature, indicating a mixture of both processes. [ABSTRACT FROM AUTHOR]

The Litopterna is a group of endemic South America ungulates that lived from Late Paleocene (Itaboraiense)to Late Pleistocene (Lujanense). The order is divided in two large groups based on dental features: the Bunolipterna,in which the Protolipternidae is placed, is composed by taxa with primitive bunodont teeth; and the Lopholipterna,grouping taxa with derived lophodont teeth. In both the postcranial morphology is derived and uniform since the earlyforms. The Itaborai Basin, located at São José district, Itaboraí city, Rio de Janeiro state, is filled with different kinds oflimestones, cut vertically by fissure fill deposits, where most of the fossils were collected. Protolipterna ellipsodontoideswas described in 1983 based on dental features, but later postcranial bones were associated to this species. The main goalof this article is to infer the foot posture of P. ellipsodontoides. The material studied consists of femora, astragali, calcaneaand metatarsals III, comprising 165 bones. All fossils were deposited in the fossil mammal collection of Departamento Nacional da Produção Mineral, in Rio de Janeiro state, Brasil. The methodology employed consisted of 15 linear and curvilinear measurements, which were submitted to a multivariate analysis (Principal Component Analysis - PCA and Discriminant Function Analysis - DFA). The results suggested a digitigrade posture to P. ellipsodontoides. Other morphological features of the skeleton, associated with a digitigrades posture, are suggestive of a cursorial locomotion, but with probable saltatory habits.

Abstract: The record of pre-Quaternary travertines is restricted to relatively few publications in the geological literature. In this paper, the authors present a petrographic and geochemical study of Paleocene travertines partly exposed in the Itaboraí basin, a small half-graben of southeastern Brazil. Travertine lithofacies were defined mainly from borehole samples, and these data were integrated with available field information. The most representative lithofacies of the travertine system are crystalline crusts that developed around springs at the surface and close to the fault. Other lithofacies, such as pisoid, micritic, and lithoclast travertines and tufas, were deposited distally from the springs. Mn and Fe carried to the surface by rising waters were incorporated in CL-zoned fibrous calcite and precipitated as iron-bearing minerals, respectively. Both goethite in the crystalline crusts and pyrite in the micritic travertine probably formed under biotic mediation. The evolution of this travertine system was related to Cenozoic reactivation of a shear zone in the Precambrian basement at the southern border of the basin. 87Sr/86Sr ratios indicate that groundwaters interacted with subsurface Precambrian marbles and gneisses before reaching the surface. δ13C and δ18O data suggest that several factors influenced carbonate precipitation in distal settings and that crystalline crusts formed from waters that changed in composition in the spring outlets and/or downflow within the travertine system. [Copyright &y& Elsevier]

Resumo: Em 1995, foi criado na área da bacia de Itaboraí, o Parque Paleontológico de São José, com objetivo de preservar a história, os afloramentos e os fósseis remanescentes do período em que esta bacia foi explorada para extração de calcário. Com o intuito de ampliar o entendimento pela comunidade da importância deste parque, foram desenvolvidas atividades utilizando jogos adaptados a uma linguagem didática. As atividades foram planejadas de forma a atingir diferentes faixas etárias e compreenderam: jogo “tipo” dominó - ligação de imagens a textos referentes à história da bacia, dos pesquisadores e um pouco da sua biota; jogo da memória - através de imagens de fósseis da bacia, os participantes puderam se familiarizar com a biota que viveu em Itaboraí há 60 Ma; quebra-cabeças - com imagens da reconstituição em vida de fósseis encontrados na bacia; jogo evolução da vida na Terra - jogo de tabuleiro contando um pouco das modificações ocorridas durante evolução da vida na Terra e localizando a Bacia de Itaboraí neste contexto. A atividade que mais atraiu o interesse dos participantes foi a simulação do trabalho do paleontólogo em laboratório. Para esta, foram confeccionados moldes em gesso de um bloco de rocha contendo um fragmento fóssil no seu interior. Este deveria ser “procurado” com o auxílio de instrumentos apropriados utilizados na pesquisa paleontológica. As atividades demonstraram, de forma geral, êxito no alcance dos objetivos pretendidos, dada a grande receptividade e interesse dos jovens e crianças frente às atividades desenvolvidas. Todas as atividades proposta podem ser adaptadas e aplicadas para outros fins.

Abstract: Riostegotherium yanei from the Itaboraí Basin, Brazil, is the oldest known Xenarthra. This paper aims to describe the internal morphology of the osteoderms of Riostegotherium yanei from the perspective of histology and micro-CT approaches, expanding the available data on cingulate osteoderm microstructure. Seven osteoderms of R. yanei were used for the internal microstructure description and eight of Dasypus novemcinctus for comparison. The osteoderms of Riostegotherium yanei lacks the diploë-like structure typical of glyptodonts but has a three-layered structure composed of two layers of non-Haversian compact bone enclosing a central layer of primary and secondary osteons. This internal organization is distinct from other Astegotheriini of comparable age, but similar to Dasypus. The 3D reconstruction of Riostegotherium yanei revealed two patterns of internal organization. Pattern 1 of movable osteoderm is composed of large remodeled areas at the base and a more compact bone at the tongue; in Pattern 2 (both movable and buckler), the internal cavities are much smaller, more numerous, and more interconnected to each other. In one buckler osteoderm, the cavities are organized somewhat radially with a compact central region (Pattern 1). Pattern 1 of both movable and buckler osteoderms resemble that of Dasypus.