Theropod teeth from the upper Barremian (Lower Cretaceous) of Vadillos-1, Spain

Abstract

The upper Barremian (Lower Cretaceous) palaeontological site of Vadillos-1 is located in the North of the Cuenca Province, Spain. It includes a sedimentary succession in “Weald” facies of brown and grey mudstones and red clays, corresponding to an alluvial-palustrine muddy floodplain. Among the collected fossils, there are several vertebrate remains belonging to theropod dinosaurs, including some teeth (VD1-197, VD1-178, VD1-179, and VD1-180) that are described and identified for the first time. The taxonomic assignment was approached following two methods beside the classical consideration of their overall morphology: a cladistic analysis performed on a tooth-based data matrix, and a discriminant analysis performed on a large dataset including measurements of non-avian theropod teeth. The DSDI > 1.2 and the braided enamel present seen in VD1-197 suggest that the specimen belongs to a Dromaeosauridae or a non-tyrannosaurid Tyrannosauroidea, but the cladistics analysis classifies this tooth in the latest. The analysis showed that VD1-178, VD1-179 and VD1-180 can be ascribed to Dromaeosauridae. The dental features characteristic of this clade and present in our specimens include a DSDI > 1.2, labial and lingual depressions, and a braided enamel surface texture, which allows to place these teeth more specifically within the Eudromaeosauria. The results show, for the first time, the presence of dromaeosaurids and possibly non-Tyrannosaurid Tyrannosauroidea at Vadillos-1, thus providing new data to the European Barremian record, and contributing to the updating the geographic distribution of these dinosaurs.