Nematherium (Xenarthra, Mylodontidae) as a guide fossil of the Burdigalian stage/age (Early Miocene) of the south of South America: the record from the Pinturas Formation, Santa Cruz Province, Argentina

BRANDONI, DIEGO; NOVO, NELSON M.; TARQUINI, JULIANA; TEJEDOR, MARCELO F.

La Plata

Jornada; Reunión de comunicaciones de la Asociación Paleontológica Argentina 2019; 2019

FCNYM-UNLP, APA, Fundación MLP "F. P. Moreno", UNLP

The Pinturas Formation (Burdigalian, Early Miocene) crops out at several localities in the upper valley of the Pinturas river, northwestern of the Province of Santa Cruz, Argentina. It is divided into three sequences (lower, middle, and upper) and the recorded fauna mainly consists of mammals. The aim of this contribution is to present the first record of Nematherium Ameghino, 1887 (Xenarthra, Mylodontidae) from the middle sequence of the Pinturas Formation at the localities of Portezuelo Sumich Norte, Portezuelo Sumich Sur, and Cerro de los Monos. The morphology and size of the specimens herein presented (MPM-PV 17420- MPM-PV 17425, deposited in the Museo Regional Provincial Padre Manuel Jesús Molina, Río Gallegos, Argentina) are similar to those of the species of Nematherium: 1) in the skull, the tooth row diverges anteriorly and the palate is flat ahead of M3 and markedly convex behind the M3; 2) the shape of the m1?m3 is similar to that of other species; 3) differences are related to the shape of the m4 (anterior lobe with concave borders and posterior lobe more oval, elongate, and obliquely oriented). The similarities and differences allow referring specimens from the Pinturas Formation to Nematherium sp. In addition to the record from the Pinturas Formation, Nematherium was recorded during the Burdigalian Stage/Age (early Miocene) at several localities of the Santa Cruz Formation, the upper levels of Sarmiento Formation (Argentina), and from the Cura-Mallín and Palomares formations (Chile). Nematherium is a guide fossil for the Burdigalian Stage/Age of the south of South America.