What are these features are an example of upon close examination of the skeleton of an adult python a pelvic girdle and leg bone can be observed?

The presence of a pelvic girdle and leg bones in an adult python is an example of vestigial structures. These are anatomical remnants that were functional in ancestral species but have lost their original purpose through evolution. In pythons, these structures indicate a historical lineage that possessed limbs, though the modern snake has adapted to a limbless form for its environment and lifestyle.