Notoungulate faunas of Northwestern Argentina: recent findings on Eocene early-diverging forms from Geste Formation

GARCÍA LÓPEZ, DANIEL ALFREDO; BABOT, MARÍA JUDITH

JOURNAL OF SYSTEMATIC PALAEONTOLOGY

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2014 p. 1 - 23

1477-2019

The vertebrate bearing deposits of Geste Formation (late Eocene) crop out in the Puna of Catamarca and Salta, Northwestern Argentina, and have yielded specimens of a variety of clades. Among these, mammals have particular importance, since their record shows some taxonomic peculiarities when compared with that of adjacent units. We present new materials including Notoungulata of generalized morphology, two morphotypes of basal typotherians, and two interatheriid taxa (including Antofagastia turneri gen. et sp. nov.). These findings increase the variety of groups and bring new information about previously known taxa for this unit. Three phylogenetic analyses with different taxonomic contexts were performed. The first analysis includes the specimen referred as Typotheria indet. A in a data-matrix of Paleogene notoungulates, involving taxa traditionally referred as ?Oldfieldthomasiidae?. The specimen is grouped together with three ?oldfielthomasiids? in the resulting tree (Maxschlosseria, Ultrapithecus, and Dolichostylodon). The second analysis involves the specimens referred as Typotheria indet. B, ?archaeohyracids?, mesotheriids, and hegetotheriids. In the result, these fossils are part of a basal polytomy of ?early archaeohyracids?. Finally, a third analysis was conducted with Interatheriidae as ingroup. Antofagastia turneri is located at the base of a node including extra-Patagonian forms of non-interatheriines interatheriids plus Eopachyrucos and interatheriines. Although Antofagastia, Punapithecus, and Chilean extra-Patagonian forms share some features, such as small size, they do not conform a separated clade. The notoungulate record of Geste shows some singularities in the context of northwestern Argentinean Paleogene units, being the presence of interatheriids and ?archaeohyracids? the most striking of these. The differences exhibited can be partially explained by temporal factors, since recent isotopic data points to a late Eocene age for this unit. Additionally, biogeographical isolation represents another possible explanation, because these levels appear to be deposited in an isolated geographic and geological context, suggesting intermontane basin deposition or local wedge-top basins.