The end-Cretaceous dinosaur succession in Europe: The Tremp Basin record (Spain)

Abstract

The succession of Maastrichtian deposits in the Tremp basin (South Pyrenean area, Spain) has provided long sections, with numerous dinosaur sites found in the Arén and Tremp Formations. The dinosaur record consists on titanosaur sauropods, dromaeosaurid theropods, hadrosaur ornithopods (including lambeosaurines) and nodosaurid ankylosaurians. Correlation of the sections enabled a clear succession of dinosaur localities to be established and thereby the succession of dinosaur faunas. Titanosaur remains, are present throughout the series, but are particularly abundant in the basal strata. Theropods and hadrosaur ornithopods are found all through the series. Lambeosaurine hadrosaur remains are restricted to sandstone channel beds close to the K/T boundary. The palaeoenvironmental conditions in each site were deduced from the sedimentological study, which allows establishing a relationship between environments and dinosaur taxa, and thus the over- or under-representation of taxa in the vertical succession to be unravelled. Titanosaurs and ornithopods are common in (but not exclusive to) marine-to-continental transitional and continental environments, respectively. Ankylosaurians are so far restricted to marine-to-continental transitional environments, but the sample is scarce. The fossil richness and the possibility of correlations among the different local sections make the Tremp Basin one of the best places in Europe to understand the final history on non-avian dinosaurs. The fossil record from the Tremp Basin suggests that they were well-diversified during the whole Maastrichtian until their extinction (as observed in North America and Asia). Sauropods were still present at the end of the Maastrichtian and lambeosaurines occurred at least in the upper part of the Maastrichtian.