What makes snake skeletons unique?
There are quite a few things that make snake skeletons so unique. The major things that separate a snake skeleton from any other mammal or reptile are their number of vertebrae and ribs, their flexible spines, and their lack of almost any other skeletal structure. These adaptations, combined with a few others, have allowed snakes to have some of the most unique shapes and methods of locomotion on earth. Let’s take a look at these differences in-depth and discover even more about what makes snake skeletons so unique.
Jaws that can unhinge
One of the key factors that have allowed snakes to become such successful hunters is their ability to unhinge their jaw. Generally, snakes will kill prey that is larger than their body is wide. This would pose a real problem for a human, so our solution is to cut things up and chew them. A snake’s solution is a bit different. When a snake catches prey that is significantly larger than their mouth and body, they use a process known as “gaping.” Gaping allows snakes to open their jaws wider than their body so they can swallow prey that they ordinarily wouldn’t be able to. This process all comes down to the jaw. In humans (and all other mammals), the lower mandible is fused to the skull. This allows humans to exert greater strength when we need to do things like chew or bite. For a snake that doesn’t have flat teeth, however, chewing isn’t all that important. Their solution is to have an unfused mandible that is only connected by stretchy ligaments. Humans can open their jaw around 26° from a neutral position. A snake, however, can open theirs 160°.
Hundreds of vertebrae
One of the other adaptations that snakes have is their many vertebrae. Vertebrae are the bones that vertebrates have along a central spinal cord. Animals that don’t have these bones are known as “invertebrates” and are generally older from an evolutionary perspective (spines are a more recent development on the earth). Snakes are vertebrates, meaning they have a spine and vertebrae. What makes them special is how many vertebrae they have. Humans have 33 stacked vertebrae that protect our spinal cord and house all the nerves that allow us to move. Snakes have 100-450 vertebrae in their bodies and between 10-205 vertebrae in their tails. With so many vertebrae, snakes have a significantly wider range of motion than a human would. An easy way to imagine it is to take a stick that has 3 jointed segments. Each joint allows a certain degree of motion, but not a lot. An easy way to give the stick a larger range of motion is to add more joints. A stick with 100 joints would be able to bend further than a stick with 3. At a certain point and with enough joints, you would be able to curl that stick into a circle. For a snake, this is the benefit of having so many vertebrae.
Hundreds of ribs
Although vertebrae make up the most important part of a snake’s skeleton, there is a little more to it. On each vertebra on a snake is a set of ribs, just like a human. Humans have 24 ribs that protect the important organs within, as well as provide structure to house those organs. Snakes have two ribs attached to every single vertebra that they have, meaning that a snake with 200 vertebrae would have 400 ribs. These small, flexible ribs can stretch and bend to a certain extent, aiding in the snake’s mobility. Additionally, when a snake eats a large meal that is larger than its body is wide, the stomach of the snake can stretch since the ribs are flexible enough to give it extra room. This is easily seen as a large lump on a snake after a large meal. The only place on a snake that doesn’t have ribs is on its tail. Even though they have vertebrae there, there aren’t any organs to protect, so they aren’t needed!
Strong bones
One of the key elements to a snake’s success is the bones themselves. One of the main methods of hunting for snakes is through constriction. Constriction is a process where a snake wraps itself around its prey and begins to slowly squeeze, tightening its grip each time the prey exhales. This type of hunting requires immense strength in the muscles as well as the bones. For a boa constrictor or anaconda hunting animals that weigh up to 100 lbs, being able to squeeze the life out of it would require incredibly strong bones and muscles. In a body, the muscles are attached to bones and require them as an anchor. The strength of snake muscles requires a skeleton that can take the stress.
Vestigial legs
Although snakes don’t have legs today, they used to millions of years ago! When we look at a snake, we don’t see any legs, but through careful observation, we can find what used to be legs a long time ago. Known as “vestigial” legs, some snakes use these small protrusions to get a grip on potential mates, namely pythons and boas.
