Snakes are vertebrates, meaning they possess an internal skeletal structure that includes a vertebral column. This internal skeleton provides foundational support and framework for their body, enabling their characteristic movements and overall survival.
Anatomy of the Snake’s Backbone
A snake’s backbone, or vertebral column, extends the entire length of its body, from head to tail. This structure is composed of individual bones called vertebrae, often ranging from 175 to over 400, and in some species, even exceeding 600. Each vertebra is connected to its neighbors by flexible joints, including a ball-and-socket joint and additional interlocking processes, which allow for a wide range of motion.
Almost every vertebra in the main body section is paired with ribs, providing both structural support and protection for internal organs. Unlike mammals, these ribs do not connect in the front to form a sternum or breastbone, which grants snakes exceptional flexibility. This arrangement ensures that the vertebral column is both strong and adaptable, forming the central axis for all their movements.
How the Backbone Enables Movement
The high number of vertebrae and their flexible joints allow snakes to perform an impressive array of movements. Muscles attached to the ribs and vertebrae work in coordination with the backbone to facilitate diverse forms of locomotion. This intricate musculoskeletal system enables snakes to bend, coil, and stretch their bodies.
Snakes employ several distinct modes of movement, often switching depending on the terrain:
- Lateral undulation, commonly known as serpentine movement, involves the snake pushing off irregularities in the surface to create a wave-like motion.
- Rectilinear locomotion allows larger snakes to move in a straight line by alternately lifting and pulling their belly scales forward.
- Sidewinding is a specialized technique used on loose or slippery surfaces, where the snake lifts and throws loops of its body sideways.
- Concertina movement involves the snake bunching its body to anchor a section, then extending another part forward, commonly used in confined spaces or for climbing.
The backbone’s flexibility is also key for actions such as constricting prey, striking, and navigating complex environments.
Snakes Compared to Other Legless Animals
The legless appearance of snakes can sometimes lead to confusion with other creatures that lack limbs. However, snakes are distinctly classified as vertebrates due to their backbone, setting them apart from invertebrates like earthworms. Earthworms, for instance, lack an internal bony skeleton and move through muscular contractions against a hydrostatic skeleton.
Legless lizards, despite their similar appearance, are distinct from snakes, though both are reptiles and possess backbones. Legless lizards often retain features absent in snakes, such as eyelids and external ear openings. Furthermore, legless lizards typically have a shorter body and a much longer tail compared to snakes, and some can even detach their tails as a defense mechanism, which snakes cannot do.