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-The Adamantina Formation deposits (Upper Cretaceous) from the Bauru Basin, in southwestern São Paulo State, have revealed an extraordinary and well preserved assemblage of fossil turtles. In this contribution some new unique findings from these deposits and the Bauru Basin, are reported and discussed. Additionally, some peculiar sedimentary structures, as a bone fragment crossing two sedimentary layers, associated with the fossils, are described and biostratinomic considerations regarding these materials are made. The turtle remains from the studied outcrop have undergone short subaerial exposure and transport, being quickly buried. It was also verified that the time elapsed between these sedimentary episodes, in one of the samples, was almost instantaneous.Key words: Testudines, Upper Cretaceous, Adamantina Formation, biostratinomy, Brazil.RESUMO -Os depósitos da Formação Adamantina (Cretáceo Superior) da bacia Bauru no sudoeste do Estado de São Paulo, apresentam uma extraordinária e bem preservada quantidade de testudinos fósseis. Neste trabalho são comunicados novos e únicos achados provenientes desta região e da bacia Bauru. Adicionalmente, são descritas peculiares estruturas sedimentares, como um fragmento ósseo atravessando duas camadas sedimentares, associadas às amostras coletadas, e são tecidas considerações bioestratinômicas referentes a estes materiais. Os fósseis do afloramento estudado sofreram um curto período de exposição subaérea, pouco transporte e foram soterrados rapidamente. Constatou-se também, que o tempo transcorrido entre estes eventos deposicionais, em uma das amostras, foi praticamente instantâneo.

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Material from a new titanosaur from the Bauru Basin (Bauru Group), Brazil is described and compared with well-known titanosaurs. Adamantisaurus mezzalirai gen. et sp. nov. is based on six articulated anterior caudal vertebrae and two haemapophyses collected from the Adamantina Formation, which is considered to be Campanian-Maastrichtian? in age. Adamantisaurus mezzalirai is characterized by the following combination of characteristics: anterior caudal vertebrae with straight or slightly backwardly-projecting neural spines with strongly expanded distal ends, stout prespinal lamina, very wide pre-and postzygapophyseal articular facets, and concave postzygapophyseal articular facets on anterior caudal vertebrae. Although our cladistic analysis has produced equivocal results, Adamantisaurus mezzalirai shares with DGM 'Series B' (Peiró polis titanosaur) and Aeolosaurus the presence of postzygapophyses with concave articular facets, and shares with DGM 'Series B' the presence of laterally expanded neural spines and stout prespinal lamina. Additionally, A. mezzalirai shares with DGM 'Series' C (other titanosaur from Peiró polis) the presence of short neural spines.

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