FIGURE 1. The phylogenetic placement of reference fossils (full red arrows) relative to modern groups for 1, Macropodoidea; 2, Monotremata; 3 Caviomorpha-Phiomorpha; and 4, Chiroptera. These clades are shaded grey and black circles identify the calibrated nodes. Relationships among modern taxa are taken from the DNA analysis of Meredith et al. (2011), although each is supported by a broad consensus of molecular phylogenetic studies. Dotted red arrows (1, 3, 4) indicate possible alternative placements for the reference fossil that if they can be confirmed, would offer (tighter) calibration of a slightly younger node.