Paleobiogeografía y paleoecología de los mamíferos continentales de América del Sur durante el Cretácico tardío-Paleoceno: una revisión

Abstract

The purpose of this paper is to outline the most recent advances in the knowledge of paleobiogeography and paleoecology of the South American continental mammals during the late Cretaceous-Paleocene span. Two basic parameters were considered: (1) taxonomic richness; and (2) trophic diversity. The genera recorded in the four «land-mammal Ages» (SALMAs) that represent the late Cretaceous-Paleocene span, i.e., Alamitian (late Cretaceous), Tiupampian (early Paleocene), Itaboraian (middle Paleocene), and Riochican (late Paleocene), were used as analytical units. As conclusion, is possible to point out that: 1) During the Alamitian SALMA the faunistic composition of South America was markedly different of that of the holarctic continents, due to the exclusive presence of pre-tribosphenic taxa of pangeic jurassic ancestry, although mostly showing a marked degree of endemism. 2) The tiupampian fauna was basically characterized by the absence of most of the alamitian pre-tribosphenic groups (except the gondwanatherian «multituberculates») and by the presence of a «mix» of taxa with narrow relationships with North America (e.g., pantodonts) in association with other proper of South America but with holarctic (e.g., marsupial s) or eastern gondwanic ancestry (i.e., monotremes). 3) The most marked compositional change in the South American mammal fauna was recorded between the Alamitian and Tiupampian SALMAs. 4) Beginning to the Itaboraian SALMA, the South American mammal fauna newly shows a marked endemic character that will distinguish all the continental mammal faunas throughout the rest of the Cenozoico 5) The absence of xenarthrans in the pre-itaboraian mammal- bearing sediments is particularly surprising. 6) The diversity of trophic types increases from Alamitian to Riochican SALMAs, because of the progressive occupation of the empty adaptive zones after the dinosaurs extinction, and the opening of new ones. 7) The «cast- of the trophic types observed in South America beginning with the Tiupampian SALMA is radically different to that recorded in the holarctic continents. The placental are restricted to the herbivorous adaptive zones, while marsupial s successfully fill those of the carnivorous, insectivorous, and rodentiform ones. This South American distribution of trophic types would be related with the peculiar physical history of the continent, characterized by vast intervals of isolation with North America, sporadically interrupted by short lapses of intercontinental connection.