Manuel Alfredo Medeiros

Oxygen isotope evidence for semi-aquatic habits among spinosaurid theropods

Spinosaurs 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 ichthyophagy and aquatic habits of spinosaurids may have allowed them to coexist with other large theropods by reducing competition for food and territory.

A new genus of dipnoiformes from the Cretaceous of Brazil

The Alcântara Formation, an important stratigraphic unit from the early Cenomanian of Brazil, was deposited under transitional (estuarine) conditions, and its fossil record includes fragmentary remains of plants, fishes, crocodylomorphs, pterosaurs and dinosaurs, with a noteworthy diversity of dipnoiformes tooth plates. The dipnoiformes material reported here comprises a new taxon, Equinoxiodus alcantarensis, gen. et sp. nov. Most of the identified morphotypes of continental vertebrates collected in the Alcântara Formation are similar to chronocorrelative faunas from Northern Africa, but this new genus of Dipnoiformes indicates some degree of paleogeographic isolation and endemism. This was probably caused by the widening of the equatorial Atlantic Ocean during the early Cenomanian, which may have selectively affected some species.

New plant fossils from the Lower Cretaceous of the Parnaíba Basin, Northeastern Brazil: Southern Laurasia links

Manuscript ID: 20170071. Received on: 05/20/2017. Approved on: 01/04/2018. ABSTRACT: This study reports on the presence of a diverse set of gymnosperm and angiosperm macrofossils from the Codó Formation, Parnaíba Basin, whose assemblage was previously known only by the occurrence of pollen grains, spores, wood fragments, leaves and roots associated with Nympheaceae. In the Brejo municipality, northeastern Maranhão State, marl levels attest a transitional to marginal lacustrine environment, with occasional marine ingressions, demonstrated by the presence of crustaceans, gastropods and fishes. The plant fossils are preserved exclusively by molds and impressions, and its diversity is represented by few specimens, suggesting taphonomic processes of selection and transportation. The taphoflora is composed of Gnetales (?Drewria), conifers (Cupressinocladus and Brachyphyllum), and basal angiosperms (Nympheales, Magnollids, and/or basal Eudicots), which support an upper Aptian – ?Albian age. It displays affinities with both the well-known flora of the Araripe Basin (Santana Formation) as well as those ones identified in deposits from the south of North America (Potomac Group), suggesting that terrestrial links persisted in the equatorial areas of the Pangea at the end of the Early Cretaceous.