FIGURE 1. Time-calibrated phylogeny of Serpentes based on Pyron et al. (2013) and Reynolds et al. (2014). Numbers represent calibrated nodes in text. Fossil taxa are the calibration points for their respective nodes. Thickened bars represent well-sampled, taxonomically resolved stratigraphic distributions for the sister taxa to Pan-Serpentes and snake lineages whose first occurrences are determined by older sister taxa. Thin bars represent estimated stratigraphic distributions for taxa with poorly resolved fossil records, or no published fossil record (names in grey). “Scolecophidia” represents a paraphyletic grade with respect to Alethinophidia (see text).