Theropod teeth palaeodiversity from the uppermost Cretaceous of the South Pyrenean Basin (NE Iberia) and the intra-Maastrichtian faunal turnover

Abstract

The South Pyrenean Basin has yielded abundant dinosaur and penecontemporaneous vertebrate fossils, becoming one of the most important areas in Europe for the study of these faunas. The studied isolated theropod teeth from the Western Tremp Syncline (NE Iberia) were recovered from the uppermost Maastrichtian (topmost Arén and Tremp formations). The studies conducted have led to the identification of eight tooth morphotypes, which are referred to cf. Paronychodon, cf. Richardoestesia, an abelisaurid, a dromaeosaurid, and a non-dromaeosaurid paravian. Together with the previously reported troodontid and ornithuromorph, this study increases the known theropod palaeobiodiversity in the area to seven taxa. The latest Maastrichtian theropod fauna of the Western Tremp Syncline is thus composed of a medium to large-sized abelisaurid as well as a high diversity of small-bodied early-branching coelurosaurians and avialans, as seen in other Ibero-Armorican localities. Revision of the literature concerning the theropods of the Ibero-Armorican domain indicates that, although similar theropod groups were present before, during, and after the intra-Maastrichtian faunal turnover (an event constrained to between the early Maastrichtian and the early late Maastrichtian; lower part of C31r to the C30r/C30n reversal), there were changes in the abelisaurid, dromaeosaurid, and large avialan assemblages, as well as in the proportions of indeterminate paravian and cf. Richardoestesia morphotypes, with the presence of troodontids only recorded in post-turnover faunas. These changes suggest that theropods might have been affected by the turnover event. Nevertheless, further studies and more complete specimens could shed more light on the effects of this faunal turnover, and on the affinities and palaeobiodiversity of the latest Cretaceous Ibero-Armorican theropods.