ORIGINS, RADIATIONS, AND DISTRIBUTION OF SOUTH AMERICAN MAMMALS: FROM GREENHOUSE TO ICEHOUSE WORLDS

GOIN F. J.; GELFO J. N.; CHORNOGUBSKY, L.; WOODBURNE, M.; MARTIN, T.

Bones, clones, and biomes: an 80-million year history of modern Neotropical mammals ed.New York : University of Chicago Press, 2010

University of Chicago Press

Lugar: Chicago, USA; Año: 2012; p. 20 - 50

Two major factors preclude a better understanding of the evolution of mammals in South America: first, the still extremely scarce Mesozoic fossil record; second, the fact that for most of the Mesozoic, and for large parts of the Cenozoic, mammalian fossils are known from a single region: Patagonia. This region, as well as the southern portion of the Andean Range, is better characterized in biogeographical terms as part of the Austral Kingdom, distinct from the Neotropical Region (Holotropical Kingdom); the former can be traced back deeply into early Mesozoic times. At least five successive phases in South American mammalian evolution can be envisaged, the oldest one being largely hypothetical: (1) Early Gondwanan (?Late Triassic-Early Cretaceous): its mammals are of Pangaean (triconodontids with amphilestid affinities) and Gondwanan (autralosphenids) origin. (2) Late Gondwanan (Late Cretaceous): strong endemism in most lineages of Pangaean (Dryolestida) and Gondwanan (Gondwanatheria) origin. (3) Early South American (?latest Cretaceous-latest Eocene): major radiations within Metatheria and Eutheria. (4) Late South American (early Oligocene-middle Pliocene): standardization of relatively few lineages among metatherians, strong radiation of hypsodont types among South American native ungulates. Finally (5) Interamerican (late Pliocene-Recent): mixture of North and South American therian lineages, progressive decline of native faunas. Among the biotic and abiotic events that triggered these phases there are: the last global warming event at the beginning of the Late Cretaceous (between phases 1 and 2); an intermittent connection between North and South America by the Late Cretaceous, favoring the First American Biotic Interchange (FABI), and the decline of native non-therians (between 2 and 3); global cooling and full development of the Circumpolar Antarctic Current, and arrival of platyrrhines and caviomorphs (between 3 and 4); finally, the Panamanian connection between the Americas and the beginning of the Great American Biotic Interchange (GABI) (between 4 and 5).