Molecular timing of the xenarthran radiation and Tertiary major environmental changes in South America. Phylogenetic relationships and divergence times are represented by a chronogram, whose branch lengths are proportional to time units, obtained from the partitioned analysis of the complete ADRA2B + BRCA1 + VWF (codon positions 1+2+3) placental dataset (5130 sites). Confidence limits on divergence time estimates are represented by rectangles at nodes corresponding to ± one standard deviation (see Table 1). Tertiary Epoch boundaries follow the 1999 geologic timescale of the Geological Society of America . The Cretaceous/Tertiary transition (K/T) is represented by a vertical dashed bar at 65 Mya. Major Andean tectonic crises 5 are represented by grey shaded areas. Eustatic curves of sea level are from . The ocean temperature curve (in red) is based on the high-resolution deep-sea oxygen isotope record (δO18) . Node numbering refers to Table 1.