The status of Peripantostylops and Othnielmarshia (Mammalia: Notoungulata: Henricosborniidae) from the earlymiddle Eocene of Patagonia (Argentina)

VERA, BÁRBARA; MONES, ALVARO

Historical Biology

Taylor and Francis

Año: 2023

0891-2963

The Vacan fauna was defined by the fossil mammalian content of the Vacan Member (Sarmiento Formation) at Cañadón Vaca fossil locality (Chubut Province, Argentina), although several other local faunas from nearby areas (e.g., Río Chico oeste) were also attributed to the Vacan age estimated ca. 45–42 Ma time interval. This fauna contains still poorly understood native South American ungulates, such as the Henricosborniidae. This group presently includes to Henricosbornia, Peripantostylops, Othnielmarshia, Simpsonotus, Orome, and Nanolophodon, but both its definition and phylogenetic relationships remain unclear. In particular, Othnielmarshia andPeripantostylops were established as guide taxa of the Vacan fauna, but their knowledge hasremained obscure since more than 50 years. The re-study of the Ameghino’s collection andthe specimens collected by the Scarritt Pocket Expeditions in Cañadón Vaca and other nearbylocalities allows us to: 1) provide an update on the systematic status of Othnielmarshia andPeripantostylops; 2) emend their diagnoses; 3) establish comparisons with other related taxafrom the same period, proposing synonymies; and 4) recognize both taxa in several local faunas from the Sarmiento and Las Flores formations. We also highlight the variability in certain controversial characters of henricosborniids, which should be evaluated for the definition of the group.