The early Eocene climatic optimum at the lower section of the Lumbrera Formation (Ypresian, Salta Province, Northwestern Argentina): origin and early diversification of the Cingulata

FERNICOLA, J.C.; ZIMICZ, A.N.; CHORNOGUBSKY, L.; DUCEA, M.; CRUZ, L. E.; BOND, M.; ARNAL, M.; CARDENAS, M.; FERNANDEZ, M.

JOURNAL OF MAMMALIAN EVOLUTION

SPRINGER

Lugar: Berlin; Año: 2021

1064-7554

Recently, the basal beds of the lower section of the Lumbrera Formation have been referredto the early Eocene (Ypresian) based on the identification of a succession of hyperthermalevents globally dated between 52?55 Ma. Nevertheless, this section havealso been referred to the middle Eocene (Lutetian) based on the ?evolutionary stage?ofits fossil mammals. In this contribution, we present a new 238U-206Pb isochron age (46.2Ma) obtained from samples taken on various independent points across paleosol andmatrix positioned at the top of the lower section of the Lumbrera Formation. The newage is consistent with the hyperthermal scheme and constrains the deposition of thelower section of Lumbrera Fm. between 55- 46.2 Ma. In this new geochronologicalframework, we present one of the most ancient cingulate assemblages from America,recorded during the early Eocene hyperthermal. The specimens involved were recoveredfrom the lowest levels of the lower section of the Lumbrera Formation at Los CardonesNational Park, Calchaquí Valleys, Salta Province, Argentina. This cingulate assemblageis formed by the armadillos Pucatherium parvum, a species widely distributedin the Eocene of northwestern Argentina and a new taxon, Noatherium emilioi, gen. etsp. nov. In this new geochronological framework, the taxonomic composition and morphologicalvariations observed in the two species described here and their probably contemporaneousRiostegotherium yanei from the Itaboraí basin (Brazil) support an earlydiversification of the Cingulata during the Paleocene, and reinforce an intertropicalorigin for the group.