The Early Aptian (Early Cretaceous) ammonites from the Aralar Mountains, Basque-Cantabrian Basin, Northern Spain

The Aralar Mountains located in northern Spain exposes a 983-m-thick succession of sediments of Early Aptian age. The lithological succession evolves from lutites, marls, and calcarenites of the Errenaga Formation to rudist micritic limestones of the Sarastarri Formation, and finally marls, lutites, and sandstones of the Lareo Formation. Based on ammonite assemblage faunas, the Deshayesites oglanlensis, D. weissi, D. deshayesi, and Dufrenoyia furcata biozones have been identified. A transition between the deshayesi and furcata zones with the co-occurrence of the ammonite genera Deshayesites and Dufrenoyia is described in the Aralar succession and is currently unique. The ammonites are described here and correlations are made with other Tethyan regions.