Fig. 2From: Characterization of the melanopsin gene (Opn4x) of diurnal and nocturnal snakesTree topology used in codon-based likelihood models (random-site, branch-site and CmC models). Nocturnal species are represented by blue lines [56, 57, 62]. Hen, Henophidia; Cae, Caenophidia, V, Viperidae, E, Elapidae, C, colubridaeBack to article page