Microvertebrate assemblage from the Upper Cretaceous site of Lo Hueco (Cuenca, Spain): A preliminary approach.

The Konzentrat-Lagerstätteof ‘Lo Hueco’ in Central Spain represents an extremely rich and diverse upper Campanian-lower Maastrichtian fossil assemblage comprising more than 10,000 fossil remains: This has made it, in recent years, one of the most relevant European fossil sites for the study of continental vertebrate faunas. The stratigraphic succession in ‘Lo Hueco’ is primarily characterized by six levels separated by transitional boundaries of green (V), grey (G1), red (R1), grey (G2), red (R2) and brown (M) beds of marly mudstones. The sample of microvertebrates remains analysed here was obtained from the screenwashing and sorting of the sediments from the G2 bed, as it corresponds to one of the richest lithosomes in terms of abundance and diversity of vertebrate microfossils from the site. Among these fossil materials, the most prevailing are the fish, especially the conical teeth and ganoid scales from Lepisosteidae. Other fish remain, though less abundant, include lanceolate teeth attributed to Amiidae and two types of molariform teeth. The first type consists of oval and flattened teeth from Pycnodontidae, while the second type correspond to circular dome-shaped teeth similar to those of Paralbulinae. The Lissamphibia material is represented by appendicular elements such as humeri, radioulnae and tibiofibulae assigned to Anura. However, one humerus probably belongs to discoglosids due to some similarities. One small fragment with a pleurodont tooth is attributed to a scincomorph lizard. Crocodiles remain correspond to at least six tooth morphotypes that can be assigned to Allodaposuchidae teeth and Atoposauridae-like teeth. Allodaposuchids are represented by cf. “Agaresuchus” sp. and others. The atoposauridae teeth are considered as to cf. “Theriosuchus” sp. Theropod tooth specimens, despite being among the least abundant fossil remains, constitute an important part of the diversity reported here, pointing out the presence of cf. Dromeosaurinae, cf. Velociraptorinae, cf. Troodontidae and cf. Richardoestesia sp. This vertebrate assemblage is consistent with upper Campanian-lower Maastrichtian coastal shallow flooded muddy plains, which also provides a unique set of fauna that distinguishes it from other Iberian Peninsula localities.