Megatheropods as apex predators in the typically Jurassic ecosystems of the Villar del Arzobispo Formation (Iberian Range, Spain)

The limestone, sandstone and clays of the Villar del Arzobispo Formation (Kimmeridgian-Berriasian) crop out in the south of the Iberian Range (Spain), and from a palaeontological point of view, the formation is characterised by dozens of sites with dinosaur fossils. The most abundant are the sauropods and stegosaurs, while the ornithopods are scarce, and theropods (especially large-sized ones) are very rare. Described here are some fossils of large-sized theropods (a new tooth and a tridactyl trackway) found at two sites of this formation within the Penagolosa sub-basin (Maestrazgo Basin) in Teruel province. The new tooth from Formiche Alto is attributed to a large indeterminate tetanuran, possibly a megalosaurid, and is closely related to other large fossil teeth from this formation in Riodeva and Galve (Teruel) and Alpuente (Valencia). In addition, a distinctive morphology of the large-sized tridactyl footprints in the trackway found at the El Castellar tracksite at the village of the same name, allows the establishment of a new ichnotaxon, lberosauripus grandis ichnogen. et ichnosp. nov. It is easily differentiated from a number of previously named ichnotaxa and suggests the ichnological record of large theropods from the Upper Jurassic of Europe, North America and Asia can be divided into two distinct groups, whose trackmakers were probably members of Megalosauridae and Allosauridae. Keeping in mind that smaller and also different teeth related to allosaurids have been previously described, it is concluded that the dinosaur assemblages in this formation include at least two types of large-sized megatheropod tetanurans which, when fully grown, were responsible for the large-sized tridactyl footprints found in this unit. The predation pressure exerted by these theropods can be seen as a significant cause stimulating the gigantic sizes of some sauropods (like Turiasaurus and Losillasaurus) found in the same formation. (C) 2014 Elsevier B.V. All rights reserved.