HOW SPATIALLY BIASED IS THE TERRESTRIAL FOSSIL RECORD?: A QUANTITATIVE ANALYSIS USING MODERN MAMMALIAN SPECIES AS A PROXY

The long-term preservation of terrestrial fossils relies on the existence of aggradational environments, where influxes of sediment and water can rapidly cover the deceased animal and keep it buried, minimizing the likelihood of destruction. Continental sedimentary basins, located over a range of tectonic and climatic settings, are examples of such environments that allow long-term preservation. Areas outside of these basins have erosional processes that remove fossils, and, therefore, taxa found in these areas cannot be preserved into the long-term rock record. Since sedimentary basins comprise roughly 16% of continental area, the terrestrial fossil record is, therefore, likely biased toward preservation of species that live in these basins, thus significantly impacting our interpretation of the faunal record. To study this potential bias, Landsat imagery and elevation data from the Shuttle Radar Topography Mission (SRTM) were used to delineate the Chaco Plain in the Andean foreland basin, the Pantanal Basin, and upland areas surrounding these basins. The distribution of mammal species within and adjacent to these basins was modeled using MaxEnt, a program devised to estimate species distributions and preferred environmental conditions. Climate and species data used in the MaxEnt modeling were obtained through readily available databases including BIOCLIM and Global Biodiversity Information Facility (GBIF). Preliminary analysis of the dataset indicates that species assemblages within sedimentary basins are distinct differ from the assemblages outside of the sedimentary basins, thus supporting the hypothesis of a potential bias in the preserved fossil record.