Habitat reconstruction of large predatory vertebrates from the Upper Cretaceous Kem Kem Group, Morocco using strontium isotope analysis

Abstract

The Upper Cretaceous Kem Kem Group in Morocco, where the depositional environment is at the boundary between terrestrial and submerged, saltwater and freshwater, produces vertebrate fossils that may have been adapted to multiple environments, including dinosaurs, reptiles and fish. The cooccurrence of these fossils may be related to differences in habitat. Strontium isotope ratios (87Sr/86Sr), which reflect the isotope ratios of the geological species in which they grow, are useful for studying the habitats of extinct animals. In this study, we reconstructed the habitat differences of the fossil vertebrates of the Kem Kem Group, using Sr isotope analysis. The results of the elemental composition analysis showed the influence of diagenetic effects was smaller in enamel-like tissue than in the dentin. The results of 87Sr/86Sr analysis of the enamel-like tissues of the tooth fossils showed that the values for terrestrial to semi-aquatic reptiles were above 0.7090, whereas those for fish ranged from 0.7077 to 0.7085. The 87Sr/86Sr values for dentin tended to converge around 0.7090, suggesting that they were influenced by sediment-derived values.