Emerling 2017 report:
The earliest snakes lost numerous light-associated genes. Evolutionary analyses suggest dim-light adaptation in snakes preceded leg loss.
From the abstract
The evolutionary origins of snakes involved the regression of a number of anatomical traits, including limbs, taste buds and the visual system, and by analyzing serpent genomes, I was able to test three hypotheses associated with the regression of these features. The final hypothesis addressed is that the earliest snakes were adapted to a dim light niche. I found evidence of deleted and pseudogenized genes with light-associated functions in snakes, demonstrating a pattern of gene loss similar to other dim light-adapted clades. Molecular dating estimates suggest that dim light adaptation preceded the loss of limbs, providing some bearing on interpretations of the ecological origins of snakes.
Google ‘nocturnal lizards’ and what do you get?
Geckos. That confirms the results of the the large reptile tree that documents that, while snakes are not geckos, the two clades shared a last common ancestor before geckos were geckos and snakes ancestors still had legs.
Emerling CA 2017. Genomic regression of claw keratin, taste receptor and light-associated genes provides insights into biology and evolutionary origins of snakes.
Molecular Phylogenetics and Evolution 115: 40–49.