Collaborative research will be conducted between Andre Wyss (University of California, Santa Barbara) and Mark Norell (American Museum of Natural History, NY). Isolated from other continents for nearly all of the Cenozoic, there developed in South America a highly peculiar and endemic land mammal fauna that has captured the interest of evolutionary biologists and paleontologists for more than a century. An extraordinary new fauna from the Andes of central Chile falls within what previously represented the most poorly known span of the South American Tertiary record, an approximately 15 million year post-Mustersan (middle Eocene), pre-Deseadan (?late Oligocene) interval. As this span coincides with a major faunal transition, it is crucial to the understanding of several long-standing problems of phylogenetic relationship among the major groups of indigenous South American fossil mammals. The new fauna thus marks the first well represented fauna clarifying the Eocene-Oligocene transition from the continent. In addition to being of major paleobiologic importance, the new fauna bears significantly on interpretation of the stratigraphy and tectonic history in a very broad segment of the central Andes. This study has three points of focus. The first involves a continued vigorous field collection and reconnaissance program. The second concerns description of this diverse, well preserved, and highly unexpected fossil assemblage, and placement of its constituents into a rigorous phylogenetic framework. The third consists of the discovery's placement into a highly integrated geochronologic context. To that end, biochronologic, magnetostratigraphic, and radioisotopic methods will be employed.
