New records of Mylodontidae (Mammalia, Xenarthra, Folivora) from Cerro Zeballos (Collón Curá Formation, Middle Miocene), Chubut province, Argentina

Abstract

The Collón Curá Formation has a diversity of sloths comprising taxa belonging to the families Megatheriidae (Megathericulus patagonicus, Planops grandis), Nothrotheriidae (Mcdonaldocnus sp., Amphibradys guiomari), Megalonychidae (Eucholoeops sp.) and Mylodontidae (Neonematherium sp., Glossotheriopsis pascuali). The aim of this contribution is to report new records of Mylodontidae specimens collected from the fossiliferous locality Cerro Zeballos of the Collón Curá Formation. The material studied corresponds to two specimens (LIEB – PV 5336 and LIEB – PV 6029), which are represented by mandibular fragments. They are housed in the collection of Laboratorio de Investigaciones en Evolución y Biodiversidad (LIEB) of the Universidad Nacional de la Patagonia “San Juan Bosco”. These specimens were analyzed and compared to previously recorded specimens from the Collón Curá Formation, it was observed that: 1) they are smaller than those referred to Neonematherium sp. and larger than Glossotheriopsis pascuali; 2) the molariforms are rounded to oval in shape, while in Neonematherium sp. they are lobulated and in Glossotheriopsis pascuali they are kidneyshaped; 3) the molariforms are placed parallel to the dentary row, as in Glossotheriopsis pascuali, but differ from Neonematherium sp. which are placed diagonal to the dentary row. These specimens are assigned to Mylodontidae indet. based on their fragmentary condition and the lacking of diagnostic characters that allow them to be assigned to genus level. These new records expand the knowledge about the diversity of Mylodontidae for the Collón Curá Formation, particularly in the fossiliferous locality Cerro Zeballos, adding to the already recorded Neonematherium sp. (LIEB – PV 5371).