International audienceSpinosaurs were large theropod dinosaurs showing peculiar specializations, including somewhat crocodile-like elongate jaws and conical teeth. Their biology has been much discussed, and a piscivorous diet has been suggested on the basis of,jaw as well as tooth morphology and stomach contents. Although fish eating has been considered plausible, an aquatic or semiaquatic lifestyle has seldom been suggested because of the apparent lack of corresponding adaptations in the postcranial skeleton of spinosaurs, which on the whole is reminiscent of that of other large terrestrial theropods. On the basis of the oxygen isotopic composition of their phosphatic remains compared with those of coexisting terrestrial theropod dinosaurs and semiaquatic crocodilians and turtles, we conclude that spinosaurs had semiaquatic lifestyles, i.e., they spent a large part of their daily time in water, like extant crocodilians or hippopotamuses. This result sheds light on niche partitioning between large predatory dinosaurs, since spinosaurs coexisted with other large theropods such as carcharodontosaurids or tyrannosaurids. The likely ichlhyophagy and aquatic habits of spinosaurids may, have allowed them to coexist with other large theropods by reducing competition for food and territory

-Theropoda teeth can show sufficiently distinct features to be, in some cases, considered as confident diagnostic material. In this work, 275 complete or fragmentary teeth, collected at the Laje do Coringa site (Alcântara Formation), have been analyzed. In some of them, the typical spinosaurine morphology is present while in others an intriguing morphology was observed: teeth combining typical features of spinosaurines (smooth carinae with wrinkles on its base) with other characters as absolutely smooth enamel and basal cross section gently compressed labio-lingually. These different forms typify two morphotypes; a number of other teeth present variation that links them by a morphologic gradient. Morphotype 1 records the presence of spinosaurine dinosaurs in the Eocenomanian of northeastern Brazil and morphotype 2 may represent a new species of Theropoda, unknown by skeletal remains, and perhaps closely related to the spinosaurine form recorded.Key words: Dinosaurs, Spinosauridae, Cretaceous, Cenomanian, Alcântara Formation. RESUMO -Dentes de terópodes podem mostrar características suficientemente distintas para serem, em alguns casos, confiáveis como material diagnóstico. Neste trabalho, 275 dentes completos ou fragmentados, coletados no sítio Laje do Coringa (Formação Alcântara), foram analisados. Em alguns, a morfologia típica de espinossaurinos está presente, enquanto em outros uma intrigante morfologia foi observada: dentes combinando características típicas de espinossaurinos (carenas lisas com enrugamentos em sua base) com outras como esmalte absolutamente liso e seção basal levemente comprimida lábio-lingualmente. Estas formas diferentes tipificam dois morfótipos; vários outros dentes apresentam variação ligando-os por um gradiente morfológico. O morfótipo 1 registra a presença de dinossauros espinossaurinos no Eocenomaniano do nordeste do Brasil e o morfótipo 2 pode representar uma nova espécie de terópode, desconhecida por restos esqueletais, e talvez proximamente aparentada da forma de espinossaurino registrada.

South American Mesozoic snake diversity is mostly represented by genera from the Cenomanian (Najash), Santonian-Campanian (Dinilysia)

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