Biostratigraphic significance of the presence of Protypotherium cf. P. antiquum Ameghino 1885 (Interatheriidae, Notoungulata) in the late Miocene of Northwestern Argentina

Abstract

Interatheriinae (Notoungulata, Interatheriidae) includes small, rodent-like, and cursorial mammal herbivores. They are known from the early Oligocene and became abundant during the early to middle Miocene in several South American localities. Throughout the late Miocene, interatheriines were only reported by a few remains from Argentinean outcrops. Here, we present a new finding from the Chiquimil Formation, Catamarca Province (Argentina). The specimen is assigned to Protypotherium cf. P. antiquum based on the large size, high teeth imbrication, and absence of a sulcus in the lingual surface of the trigonid and talonid of p4, in comparison to late representatives of Interatheriinae. The chronostratigraphic context allows us to consider last intheratheriine records as a Last Appearance Datum (LAD), important to establish biostratigraphic and/or chronostratigraphic units in the late Miocene. The scarce interatheriine records and paleoenvironmental approaches during this lapse suggest that the C3/C4 biomass change and the radiation of the Hegetotheriidae lineage probably affected the already reduced population of interatheriines and led to their final disappearance.