What unique evolutionary throwback feature, generally non-functional, is sometimes observed on sand boas near the cloaca?

Small claws or spurs representing vestigial hind limbs

A remarkable evolutionary remnant found in some descriptions of sand boas is the presence of small claws or spurs located externally on either side of the cloaca. These structures are classified as vestigial hind limbs—external remnants indicating an ancestral lineage that possessed functional legs, typical of earlier reptiles. While these features are too small in modern sand boas to serve a primary functional role in locomotion or defense, they are fascinating markers of evolutionary history. Although largely vestigial, historical context suggests they might occasionally be employed minimally, perhaps during the intimate processes involved in mating rituals, but they do not aid in their primary fossorial lifestyle or surface travel.