The King Snake, a common and non-venomous species often encountered in North America, possesses a vertebral column that runs the entire length of its body. This internal skeleton is the defining feature that places the King Snake firmly within the biological group known as vertebrates. This bony structure supports the snake’s muscular form and enables its characteristic movements.
The Vertebrate Classification
The suborder Serpentes, which includes all snakes like the King Snake, belongs to the phylum Chordata and the subphylum Vertebrata. The defining characteristic of a vertebrate is the presence of an internal skeleton that includes a spinal column composed of segments called vertebrae. This classification separates snakes from invertebrates, such as insects or worms, which lack a backbone entirely.
Snakes are reptiles, placing them alongside other vertebrates like mammals, birds, fish, and amphibians. While their limbless appearance might suggest a simpler structure, their internal anatomy is complex and highly specialized.
Anatomy of the Snake’s Spine
The snake’s spinal column is characterized by an exceptionally large number of vertebrae. While humans have only 33 vertebrae, a snake can have anywhere from 200 to over 400 segments in its body and tail. This sheer quantity of small, individual bones provides the foundation for the snake’s extreme flexibility.
Each body vertebra is attached to a pair of ribs, which creates a protective cage and a surface for muscle attachment along the entire length of the animal. Snakes lack a sternum or breastbone, meaning the ends of the ribs are free to move. This absence allows the snake’s body to expand dramatically, an adaptation necessary for swallowing prey much wider than its own body.
The connection between each vertebra is highly specialized, featuring a complex of five different articulation points. At the center is a ball-and-socket joint, which provides a wide range of motion. Specialized interlocking structures called the zygosphene and zygantrum prevent excessive twisting or rotation of the spine. This arrangement achieves a balance, providing maximum flexibility for bending while maintaining stability against unwanted torsion.
Flexibility and Movement
The unique anatomy of the spine directly enables the King Snake’s diverse methods of travel. The massive number of small, highly articulated vertebrae allows the body to form the complex curves required for lateral undulation, the classic serpentine motion. This side-to-side bending allows the snake to push against objects in its environment, propelling itself forward efficiently.
The spinal structure also supports other forms of locomotion, such as concertina movement used for climbing or moving through narrow tunnels, and rectilinear movement, which involves moving straight ahead like a tank tread. Rectilinear motion uses the abdominal muscles to lift and pull sections of the belly scales forward without significantly bending the spine.
The powerful muscles that connect to the ribs and vertebrae are integral to these movements, acting as levers and anchors. These muscles also allow the King Snake to constrict its prey and swallow large meals, demonstrating the functional integration of the skeletal and muscular systems.