Final answer:
True, snakes evolved from a tetrapod ancestor, and certain species have vestigial structures in the form of pelvic spurs, demonstrating their evolutionary history.
Step-by-step explanation:
The statement that historically, snakes had legs and now they have vestigial structures in certain species is True. Snakes are thought to have descended from a tetrapod ancestor, which means their ancestors had four limbs. Over time, many of these legged ancestors evolved into species with highly specialized ways of moving and hunting, leading to the loss of legs in modern snakes.
However, certain snake species, like boas, retain vestigial hindlimbs in the form of pelvic spurs. This evolutionary change demonstrates the concept of vestigial structures, which are body parts that have lost their original function through the process of evolution. The presence of these vestigial features supports the theory that snakes evolved from legged ancestors.