New records on middle-late Eocene ‘didolodontids’ and Litopterna (Mammalia) from southwest Patagonia (Argentina)

Abstract

Recent fieldwork at fossiliferous levels of the Sarmiento Formation in the Cañadón Pelado and La Gran Hondonada sites (Chubut Province, Argentina) has yielded both key insights into the geographic location of a historical site and new specimens of two poorly known South American Native Ungulates from the middle-late Eocene. First, we identified the current Cañadón Pelado locality corresponding to the long-unused ‘Mallín del Gato’, which had not been referenced for over 60 years. Second, we report for the first time the presence of Didolodus multicuspis, D. magnus and Victorlemoinea sp. in Cañadón Pelado, and D. magnus at La Gran Hondonada. Notably, for D. magnus, we describe the most complete mandibular fragment recovered to date, preserving m2−m3, as well as the first p4, P3 and M1 for this species, thereby refining its diagnosis. The occurrence of D. magnus highlights taxonomic similarities not only between the upper levels of Cañadón Pelado and La Gran Hondonada, but also between these and the La Gran Barranca (GBV60 level). Additionally, the co-occurrence of D. multicuspis and Victorlemoinea sp. in Cañadón Pelado supports taxonomic affinities with other Barrancan faunas from Chubut Province.