Besides possessing a small diameter and reduced eye size, what general ancestral trait do worm snakes share with other snakes despite their fossorial specialization?

The fundamental snake characteristics like the loss of eyelids and external ears

Even highly specialized snakes like the worm snake retain core morphological traits established during the deep evolutionary history of the entire snake order. While they have undergone extreme refinement for subterranean life—such as developing a rigid snout and reduced eyes—they still possess fundamental snake characteristics inherited from their common ancestor. These persistent traits include the absence of eyelids and the lack of external ears. These features remain consistent across the phylogeny, whether comparing a tiny *Carphophis* to a massive constrictor, demonstrating the stability of the basic snake architecture.