BIOCHRONOLOGICAL RELATIONSHIPS OF THE EARLIEST SOUTH AMERICAN PALEOGENE MAMMALIAN FAUNAS

GELFO, J.N.; GOIN F. J.; WOODBURNE, M.; DE MUIZON, C.

PALAEONTOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2009 vol. 52 p. 251 - 269

0031-0239

The oldest Cenozoic mammalian assemblages inSouth America have been recovered from levels of the HansenMember of the Salamanca Formation, Punta Peligrolocality in Argentina, and from the Santa Lucý´a Formation inTiupampa, Bolivia. These faunas led to the recognition ofthe Peligran and Tiupampan South American Land MammalAges (SALMAs), each alternatively regarded as the oldestPaleocene SALMA. Due to the lack of radioisotopic dates formammals bearing levels at these localities, no agreement hasbeen reached yet about their relative ages. In this paper, therole of mammal faunas in age inference is discussed. Analysisof the SALMAs shows that the presence of non-therianmammals in the Peligran is of little consequence to the biochronologicalevaluation, reflecting instead a relict Mesozoicdistribution. In contrast, therian mammals are particularlyimportant in that (1) they were Lauraisan immigrants and(2) they support direct comparisons between the Tiupampaand Punta Peligro faunas. Parsimony and cluster analysiswere used to quantitatively test hypotheses concerning therelative age of the Peligran and Tiupampan SALMAs. Ourresults support the hypothesis that the Tiupampan SALMA(early Danian) is older than the Peligran SALMA (earlySelandian). This alignment results in an interpretation of theevolutionary history of South American land mammals thatis more straightforward than the alternative.