Which of the following is incorrect for snakes ?

Question

Accepted Answer

The correct option is 2:
The statement "Pectoral girdle is present" is factually **incorrect** for snakes, making it the correct choice for this multiple-choice question. Snakes, which belong to the suborder Serpentes, are defined by their limbless body plan. During their evolution, they lost all traces of the complex skeletal structures that support limbs in other vertebrates. This includes the complete absence of a pectoral girdle (shoulder bones) and, with the rare exception of tiny vestigial remnants in primitive forms like boas and pythons, the pelvic girdle (hip bones) as well. The lack of these girdles is a crucial anatomical adaptation that allows for the remarkable flexibility, streamlining, and specialized movement—such as lateral undulation and burrowing—that characterize snakes.

The incorrect option is 1:
The statement "Bones of palate are movable" is **correct** for snakes and therefore an incorrect option to select. Snakes possess a highly flexible skull structure known as cranial kinesis, which is essential for their predatory feeding strategy. The bones in the roof of the mouth, or palate, are loosely articulated with the rest of the skull and the two sides of the lower jaw are not rigidly fused at the chin. This arrangement allows the snake's mouth to open incredibly wide and for the upper and lower jaw bones to move independently of one another. This independent movement enables the snake to 'walk' its head over large prey during the process of ingestion.

The incorrect option is 3:
The statement "Ribs are free ventrally" is **correct** for snakes and thus an incorrect option for the question. Unlike mammals, birds, or other reptiles where the ribs connect to a sternum (breastbone) to form a rigid rib cage, snakes lack a sternum entirely. As a result, the ventral ends of their numerous ribs terminate freely within the muscle and skin of the body wall. This feature significantly increases the flexibility of the body, which is necessary for locomotion. Furthermore, these free rib tips are connected to the large, specialized ventral scales, and their movement plays a key role in the forward propulsion of the snake by providing grip on the substrate.

The incorrect option is 4:
The statement "Snakes are sensitive to air borne vibration" is **correct** for snakes and is an incorrect option to choose. While snakes lack the external ear openings and tympanic membranes (eardrums) common in many animals, they are not deaf. They are highly attuned to vibrations, primarily detecting low-frequency seismic or ground-borne vibrations through their jaw bones and the sensory receptors throughout their body. However, scientific research has confirmed that the snake's inner ear is capable of detecting low-frequency *air-borne* sound waves as well, with the vibrations being transmitted through the jaw bone and the quadrate bone to the cochlea. This system allows them to perceive certain acoustic signals in their environment.