The phylogenetic relationships and fossil record of early lepidosaurs compared to molecular divergence estimates. Estimates for the origin of Lepidosauria based on previous molecular studies are listed on the right in blue with short arrows. Estimates for the origin of crown group Squamata are listed on the right in red with long arrows. Timescale based on Gradstein et al. . Fossil records include those described, or referred to, in Butler et al. , Carroll , Clark and Hernandez , Colbert , Evans [8, 9, 26, 33, 91], Evans and Białynicka , Evans and Jones , Evans et al., , Fraser [22, 23, 136], Fraser and Benton , Heckert et al. , Nesbitt , Renesto , Reynoso [19, 150], Robinson , Sues and Hopson , Sues and Olsen , Whiteside , and others listed in Evans et al.  and Jones et al. .