Updated knowledge on the Notoungulata (Mammalia) from the late Miocene Cerro Azul Formation, La Pampa Province, Argentina

Abstract

We describe new remains of notoungulates from the Cerro Azul Formation (late Miocene) in La Pampa Province and reassign others previously studied, helping to precise the taxonomic diversity of 25 fossiliferous localities of this formation. Geomorphological context previously described for the area provides data to place some localities in a temporal sequence. The following Notoungulata are recognised: Protypotherium minutum (Interatheriidae), Paedotherium minor, Tremacyllus impressus, Hemihegetotherium achataleptum, H. torresi, and Hemihegetotherium sp. (Hegetotheriidae), Typotheriopsis silveyrai, T. chasicoensis, and Pseudotypotherium subinsigne (Mesotheriidae), and Pisanodon nazari, Hemixotodon chasicoensis, and cf. Stenotephanos plicidens (Toxodontidae). This study allows adding new localities to the biochronological sequence previously proposed based on the evolutionary pattern of the octodontoid rodents. Chasicoan and early Huayquerian (as herein considered) faunal assemblages present higher diversity of notoungulates than those assigned to late Huayquerian. Some localities lack a representation of taxa significant enough to precise their biochronological position within the late Miocene. The difference in the notoungulates representation along the Chasicoan–Huayquerian ages may be due to climatic changes that affected the centre of Argentina from late Miocene to early Pliocene.