Purpose: An outcrop of early Cretaceous shallow water carbonates, partly rich in corals, is exposed in the Sorrozuela site, along the coast line of the Ajo Cape peninsula, Cantabria. The purpose of this work is to study the orbitolinid assemblage of these platform carbonates, which have been attributed to the Ramales Formation. Methods: For that, rock samples were collected and thin-section were analyzed from the Albian limestones of the Ajo Cape area (Sorrozuela site). Results: Thin-section analysis yielded an interesting assemblage of orbitolinids including (in decreasing abundances Simplorbitolina manasi Ciry and Rat, Orbitolinopsis ajoensis n. sp., Dictyoconus? tunesianus (Peybernès), Simplorbitolina conulus Schroeder, and Palaeodictyoconus sp., indicating a late early Albian age. D.? tunesianus is recorded for the first time from Cantabria, representing also the youngest occurrence known so far. Orbitolinopsis ajoensis n. sp. is characterized by its medium-conical test, a subdivided marginal zone, and rather small, close-set cupules in the central zone. The new species represents one of the youngest lower Cretaceous records of the genus. Conclusions: The new data provide further details on the biostratigraphic use of orbitolinid foraminifera in the Cantabrian Urgonian (Aptian-Albian) system.

Instituto Geológico y Minero de España, España