There are modern species of snakes with vestigial legs today, pythons, boas... Leglessness in lizards not very uncommon. It evolves regularly, before and after

There are modern species of snakes with vestigial legs today, pythons, boas... Leglessness in lizards not very uncommon. It evolves regularly, before and after the snake lineage likely originates. One species of such creatures became the ancestor of snakes. I think (not an expert) that the lineage of that creature is still speculative... with a still-wide range of candidates. Not sure if Plesiosaurs are still a contender, but if it is then it gives Plesiosaurs the same relationship to snakes that birds have to dinosaurs.