FIGURE 2. Composite section of the Nacimiento Formation with fossil zones and mammal biostratigraphic zonation correlated to the Geologic Time Scale (after Williamson 1996) showing the stratigraphic placement of NMMNH fossil localities discussed in the text and stratigraphic range of early Paleocene (Torrejonian) metatherian taxa reported here. The Geomagnetic Polarity Timescale is after Kuiper et al. (2008). The North American Land Mammal Age boundaries are after Lofgren et al. (2004).