New primates from the Río Santa Cruz and Río Bote (Early-Middle Miocene), Santa Cruz Province, Argentina

Abstract

Four specimens of primates were collected from the Santa Cruz Formation (Early-Middle Miocene) during expeditions undertaken by the Museo de la Plata, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, and Duke University in 2013, 2014, and 2017. A new species of Homunculus Ameghino, H. vizcainoi (Platyrrhini, Homunculidae), was identified at Barrancas Blancas, and Segundas Barrancas Blancas localities on the right bank of the Río Santa Cruz (Santa Cruz Province, Argentina). The Barrancas Blancas specimen comes from a tuff dated at 17.04 Ma; those from Segundas Barrancas Blancas are older than a tuff dated at 16.32 Ma and younger than a tuff dated at 17.36 Ma. A Río Bote specimen is confidently identified as Homunculus, but of uncertain species. All these fossil primates are temporally equivalent to those from the coastal Santa Cruz Formation, and younger than those from the Pinturas Formation to the north. By contrast, the lower and middle strata of the Pinturas Formation contain a different but closely related taxon, Carlocebus Fleagle. All known records of Carlocebus from the Pinturas Formation in north central Santa Cruz Province are older than the known occurrences of Homunculus in the Santa Cruz Formation in the Río Santa Cruz valley, Río Bote and elsewhere.