Do Snakes Have Bones? Vertebrae and Ribs of a Snake

The snake skeleton at a glance

A snake’s skeleton is essentially a skull attached to a very long, flexible spine with ribs. Early in snake evolution, the body region that carries ribs, the chest, became enormously extended, so most of a snake is effectively one long rib cage, followed by a shorter tail.

A snake with 300 vertebrae may have around 250 pairs of ribs, so its skeleton contains many hundreds of bones in total.

The backbone: hundreds of vertebrae

The number of vertebrae varies widely between species. Short, stout snakes such as some vipers have fewer, while long, slender snakes have many more. Most species fall roughly between 200 and 400. A giant such as the reticulated python is built on the same plan as a small snake, with each vertebra and rib simply much larger.

The spine has only a few clear regions. Right behind the skull are a few neck vertebrae without ribs, which support and turn the head. Then comes the long trunk, where every vertebra bears ribs. Behind the vent is the tail, whose vertebrae carry no ribs and usually make up less than a fifth of the total.

Each vertebra has a ball at the back that fits into a socket on the next, so every joint can bend a little. Many small bends add up to a body that can coil, loop and climb. Snake vertebrae also have an extra pair of interlocking joints that other reptiles lack. These let the spine bend freely from side to side and up and down, but resist twisting, which makes the backbone remarkably strong for its weight.

Ribs without a breastbone

Snake ribs are long, thin and curved. Each pair is attached by flexible joints to a vertebra, and their lower ends are free. There is no breastbone to hold them together at the front.

This open design has several uses. The ribs can spread wide when a snake swallows prey bigger than its head; see how do snakes swallow large prey? Cobras spread long neck ribs to raise their hoods, and some tree snakes splay their ribs to flatten their bodies as they glide between branches.

Ribs also help snakes move. Muscles run from the ribs to the broad belly scales, and large heavy snakes such as pythons can creep forward in a straight line by lifting and pulling these scales in waves while the ribs act as anchors. Learn more about these movements in how do snakes move without legs?

The skull and jaws

The snake skull is a light, loosely built structure of many small bones. The braincase is solid and protects the brain, but the bones of the snout, upper jaw and palate are attached by flexible joints. The lower jaw is in two halves joined at the chin by a stretchy ligament, and each half hangs from the skull by a movable bone called the quadrate.

Snakes also have a small hyoid bone in the throat that supports the tongue muscles. Their teeth, often curved backward, are replaced throughout life. In venomous snakes some of these teeth are specialized as fangs.

Leftover hip and leg bones

Snakes evolved from four-legged lizard-like ancestors, and some still show it. Pythons and boas have tiny remnants of the hip and thigh bones buried in the body near the vent. On the outside these end in a pair of small claw-like spurs, which males use to stroke females during courtship. Some blind snakes also keep traces of a hip girdle. More advanced snakes, such as the corn snake and other colubrids, vipers and cobras, have lost these bones entirely.

Fossils tell the same story. Snakes with legs, such as Najash from Argentina, which had small but well-formed hind legs, lived roughly 90 to 100 million years ago. No living or fossil snake known has front legs.

Myths about snake bones

“Snakes are just muscle and no bones.” Not true. A snake’s skeleton is extensive; it simply has no limbs.

“Snakes unhinge their jaws.” The jaw bones never come out of joint. Their loose connections and the extra quadrate hinge allow the very wide gape.

“Shed skin contains bones.” A shed skin is only the thin outer layer of the skin, including the clear eye caps. It contains no bone or muscle at all.

The skeleton explains much about how snakes live: hundreds of linked vertebrae for bending and climbing, ribs that spread to fit huge meals, and a skull that can stretch around prey far wider than the head.