The upper part of the Las Llacerias section shows an exceptionally complete sequence of Upper Moscovian (Myachkovsky) and Kasimovian (Krevyakinsky-Khamovnichesky) strata which yielded fusulinacean foraminifera from numerous beds throughout the succession. In addition to the advanced fusulinellins and primitive schwagerinins described already in a separate paper, the present work completes the study of the fusulinacean fauna with the description of additional fusulinids, schubertellinids, and ozawainellids.
The fusulinaceans of the studied part of this section provide a basis for recognizing three biozones, i.e., the Fusulinella, Protriticites and Montiparus Zones, and they allow a correlation of the Las Llacerias strata with the Moscow Basin and the Donets Basin. An early schwagerinid species intermediate between Protriticites and Triticites, found near the top of the section, points to a correlation of the uppermost part of the section with the basal Missourian of North America. Some combined studies on spores and fusulinaceans, carried out previously in this and other Cantabrian Mountains sections, give clues for a tentative correlation with the Western Europe stratigraphic scale.