Question

Which one of the following is not a tetrapods character?

• A. Dermal scales
• B. Neck and ribs
• C. Pelvic girdle
• D. Flat skull

Hint:

Think about the adaptations needed to move from water to land. You need stronger support (pelvic girdle, ribs), a way to look around (neck), but you would typically lose features adapted for water, such as fins and fish scales.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Tetrapods are the superclass of four-limbed vertebrates, which includes amphibians, reptiles, birds, and mammals. They evolved from lobe-finned fishes and share a set of key characteristics related to terrestrial life. The question asks to identify a feature that is not a typical characteristic of this group.
Step 2: Detailed Explanation:


Neck and ribs: The evolution of a neck, allowing independent movement of the head, was a crucial adaptation for terrestrial life. Well-developed ribs provide support for the body and protect internal organs, which is more critical on land than in water. This is a tetrapod character.

Pelvic girdle: A strong pelvic girdle, firmly attached to the vertebral column, is essential for supporting the body's weight on the hind limbs and for terrestrial locomotion. This is a key tetrapod character.

Flat skull: Early tetrapods, like Acanthostega and Ichthyostega, are characterized by having broad, flat skulls. This is a classic feature of early members of the group.

Dermal scales: Dermal scales are characteristic of fish. One of the major evolutionary trends in the transition from fish to tetrapods was the loss of these scales in the first amphibians, which instead developed smooth, moist skin for cutaneous respiration. While some later tetrapods re-evolved scale-like structures (e.g., reptiles), the loss of fish-like dermal scales is a defining trend for the group's origin. Therefore, their presence is not a general tetrapod character, but rather a fish character.

Step 3: Final Answer:
Dermal scales are a characteristic of fish that were generally lost in the evolution of tetrapods, and thus are not considered a characteristic feature of the tetrapod group as a whole.