what taxon are turtles most closely related to?

Answer 1

The order Testudines (turtles) is considered closest to the order Squamata (scaled reptiles) based on molecular studies. Prior to this, Testudines was considered closer to the subclass Archosauria (a group of diapsid reptiles that is represented today by birds and crocodiles and which also included the dinosaurs). The taxonomy of turtles is still disputed, though.