Timetrees inferred with MCMCtree, estimating the split between yellow and green anaconda lineages (genus Eunectes). We show these to illustrate the considerable uncertainties surrounding the evolutionary age of anacondas with the limited data available and the large differences between inferences from nuclear-encoded vs. mitochondrial DNA sequences. Analyses are based on 2150 bp of four fragments of nuclear-encoded protein-coding genes (A) and 1098 bp of the mitochondrial cytochrome b gene (B), constraining the Epicrates-Eunectes split to 15.8–37.3 Mya (secondary calibration obtained from www.timetree.org). Constraints are shown in purple, credibility intervals in light blue. Preferred age estimates of the split between yellow and green anacondas are shown in green. See Supporting information for additional analyses and detailed methods. Photo of Eunectes murinus by Frank Glaw.