1. The earliest age (23.03–20.43 Ma ago) in the Miocene epoch, preceded by the Chattian (Oligocene), followed by the Burdigalian (Int. Commission on Stratigraphy, 2004).
2. The name of the corresponding European stage, which is roughly contemporaneous with the upper Zemorrian and lower Saucesian (N. America), parts of the Otaian (New Zealand), and the upper Janjukian and lower Longfordian (Australia). The stratotype is in the Aquitanian Basin, France. The Aquitanian is itself characterized by the appearance of the planktonic foraminiferid Globigerinoides primordia.