Most people view snakes as the ultimate legless creatures, perfectly streamlined for slithering through grass, climbing trees, or swimming through waterways. However, if you look closely at the skeletal structure of primitive snakes, you will find a surprising evolutionary secret. Certain families of snakes, specifically boas, pythons, and some burrowing species, still possess vestigial hip bones and tiny, claw-like appendages. These structures are evolutionary leftovers from a time millions of years ago when the ancient ancestors of snakes walked on land.
To understand why some snakes have hips, we have to look back more than a hundred million years into the fossil record. Early snake ancestors were burrowing or marine lizards that gradually lost their limbs to better navigate tight underground tunnels or aquatic environments. While highly advanced snakes like vipers and colubrids have completely lost all traces of their limbs, primitive lineages split off earlier in evolutionary history. In these older families, the genetic blueprint for leg development was never fully switched off, leaving behind internal pelvic bones that float in the muscle tissue, completely disconnected from the spine.
Externally, these vestigial hips manifest as tiny, thorn-like claws located on either side of the snake's cloaca, the multi-purpose opening near the base of the tail. Known to herpetologists as pelvic spurs, these claws are actually the evolutionary remnants of thighs. In giant constrictors like the green anaconda or the reticulated python, these spurs are easily visible to the naked eye, especially in mature males. While they no longer serve any purpose for locomotion, they have been repurposed for other behaviors, proving that evolution rarely lets functional tissue go entirely to waste.
Today, snakes use these tiny hip claws primarily during courtship and mating. Male pythons and boas will use their pelvic spurs to gently scratch and stimulate the female during courtship, encouraging her to align her body for mating. In some species, males also use these spurs in combat with rival males, pushing and scraping against each other to establish dominance. Female snakes also possess these spurs, though they are typically much smaller and less developed than those of their male counterparts.
Finding a snake in your yard or home can be an unnerving experience, whether it is a primitive constrictor or a highly evolved local species. If you encounter an unfamiliar snake, the safest course of action is always to keep your distance and avoid attempting to handle or move the animal yourself. You can take a clear photograph from a safe distance and upload it to SerpentID, which can quickly analyze the markings and body shape against likely local species to help you identify it. If you suspect the snake is venomous or represents a safety concern, please contact your local wildlife services or a professional relocation service immediately.