Navegando por Autor "Ribeiro, Luiz Carlos Borges"

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Noasaurid theropod (Abelisauria) femur from the Upper Cretaceous Bauru Group in Triângulo Mineiro (Southeastern Brazil).
(2019) Martinelli, Agustin Guillermo; Marinho, Thiago da Silva; Egli, Federico Brisson; Hechenleitner, Esteban Martín; Iori, Fabiano Vidoi; Veiga, Fábio Hiratsuka; Basilici, Giorgio; Soares, Marcus Vinícius Theodoro; Marconato, André; Ribeiro, Luiz Carlos Borges
A new record of noasaurid theropod (Dinosauria, Abelisauria) is here described and compared, including the description of its microstructure. It consists of an almost complete femur of small size (132 mm of preserved length) discovered in 2014 in a new locality at Campina Verde Municipality, Minas Gerais state, Brazil. The new locality is named Fazenda Seis Irm~ aos-Grotas and has also provided thousands of ostracods, few fish remains, and a partial skeleton of an indeterminate baurusuchid mesoeucrocodylian. The bearing-fossil sedimentary sequence is referred to the Adamantina Formation (Bauru Group, Bauru Basin). The femur here presented represents the second putative occurrence of an unusual small-sized noasaurid abelisaur for the Upper Cretaceous Bauru Group.
Palaeoecological implications of an Upper Cretaceous tetrapod burrow (Bauru Basin; Peirópolis, Minas Gerais, Brazil).
(2019) Martinelli, Agustin Guillermo; Basilici, Giorgio; Fiorelli, Lucas Ernesto; Klock, Carolina; Karfunkel, Joachim; Diniz, Ariela Costa; Soares, Marcus Vinícius Theodoro; Marconato, André; Silva, João Ismael da; Ribeiro, Luiz Carlos Borges; Marinho, Thiago da Silva
We describe a globally rare example of a tetrapod burrow from the Upper Cretaceous Bauru Group (Bauru Basin) from Peirópolis, Minas Gerais State, Brazil. The sedimentary succession containing the burrow includes a rich vertebrate assemblage comprising fish, podocnemid turtles, mesoeucrocodylians, saurischian dinosaurs, among others. The burrow is composed of an oblique tunnel (~30°), oval in cross-section, with a horizontal and suboval terminal chamber; it is 1.3 m long from the midpoint of its inferred entrance to the midpoint of the bottom of the chamber. It occurs in the upper portion of a sandstone succession, interpreted as a braided channel deposit, and the burrow-fill comprises medium-grained sandstone with mudstone intraclasts derived from fluvial floodplain facies. it is overlain by other fluvial channel deposits. Analyses suggest that the burrow was dug after the filling of the braided channel and during the pedogenesis of its exposed upper surface. Based on burrow morphology and size, the most plausible producer of this burrow is a notosuchian mesoeucrocodylian, such as small to mid-sized notosuchians (e.g., sphagesaurids). The Bauru Group has an extensive fossil record of notosuchians with disparate morphologies, and it is noteworthy that the small-sized notosuchian Labidiosuchus amicum comes from the same unit as the burrow. Moreover, arid to semi-arid conditions have been inferred for fossil-bearing rocks of this unit, and as such the data here presented add to our palaeoecological knowledge of Cretaceous mesoeucrocodylians in Gondwana. Moreover, it constitutes a new Cretaceous record of a tetrapod burrow during a period when such ichnofossils are globally rare.
Sedimentology of a distributive fluvial system : the Serra da Galga Formation, a new lithostratigraphic unit (Upper Cretaceous, Bauru Basin, Brazil).
(2021) Soares, Marcus Vinícius Theodoro; Basilici, Giorgio; Marinho, Thiago da Silva; Martinelli, Agustin Guillermo; Marconato, André; Mountney, Nigel Philip; Colombera, Luca; Mesquita, Aquila Ferreira; Vasques, Julia Tucker; Abrantes Junior, Francisco Romero; Ribeiro, Luiz Carlos Borges
The Bauru Basin of SE Brazil is a large (ca. 370,000 km2 ) Upper Cretaceous intracratonic feature, important for its fossil remains and of particular value as a source of regional palaeoclimatic information. Historically, lithostratigraphic reconstructions have been performed mainly for successions of the central and southern parts of the basin, resulting in a lithostratigraphic scheme that is not applicable to the northernmost regions. In particular, the northeastern deposits of the Marília Formation (Serra da Galga and Ponte Alta members) reveal lithological, stratigraphic, and palaeontological differences from southeastern and northwestern counterparts (Echapor~a Member). Nevertheless, these deposits are considered as a single lithostratigraphic formation in the literature. To address this problem, this study demonstrates how the northeastern deposits of the Marília Formation do not show affinity to the rest of the unit. A more suitable lithostratigraphic model is proposed for the northeastern succession as a distinct and independent unit. Lithofacies and palaeopedological analysis, combined with lithostratigraphic mapping of the northeastern deposits, reveal 11 distinct lithofacies and three pedotypes over an area of 450 km2 . Sedimentary facies and pedotypes were assigned to six interbedded architectural elements: (a) type 1 channel fill, (b) type 2 channel fill, (c) type 3 channel fill, (d) interchannels, (e) palaeosols, and (f) calcrete beds. The succession is interpreted as a distributive fluvial system with overall direction of flow to the NNW, and which developed under the influence of a semiarid climate regime. This contrasts with deposits of the southeastern and northwestern Marília Formation, previously suggested to be of fine-grained aeolian affinity with interbedded poorly channelised deposits assigned to an aeolian sand sheet environment. By revising the existing lithostratigraphic scheme for the northeastern deposits, and contrasting them with laterally equivalent strata, this work demonstrates how the previously named Serra da Galga and Ponte Alta members reveal a unique set of lithological, architectural, and genetic signatures that permits to separate them from the Marília Formation. Finally, a new lithostratigraphic classification for the unit is proposed: the Serra da Galga Formation, whose deposition relates to an ancient distributive fluvial system.