Epidermal scales are present in :

Question

Accepted Answer

The correct option is 3: Lizard

The correct option is Lizard. Lizards belong to the Class Reptilia, a group whose primary defining characteristic for terrestrial life is the specialized structure of its skin. The lizard's entire body is covered by a dry, cornified skin that forms overlapping structures known as epidermal scales and scutes. These scales are formed from the outer layer of the skin, the epidermis, and are composed of a very tough protein called keratin. This protective, armor-like layer serves two vital functions: it offers mechanical protection against injury and, more importantly for a land animal, it acts as an impermeable barrier to prevent water loss (desiccation). This feature is a classic evolutionary adaptation that enabled reptiles to fully conquer dry terrestrial environments, distinguishing them from their amphibian ancestors.

The incorrect option is 1: Scoliodon
*Scoliodon* is commonly known as the dogfish, and it is a member of the Class Chondrichthyes, or cartilaginous fishes (sharks, rays, and skates). The body of *Scoliodon* is covered not by true epidermal scales, but by specialized structures called placoid scales, which are also known as dermal denticles. Placoid scales are structurally similar to teeth, featuring a basal plate embedded in the dermis and a spine that projects through the epidermis. Their origin is primarily dermal, making them fundamentally different from the true epidermal scales that are characteristic of reptiles like the lizard.

The incorrect option is 2: Rabbit
The rabbit is a placental mammal, belonging to the Class Mammalia. The primary characteristic covering the skin of a mammal is hair or fur, which is also a derivative of the epidermis but is structurally distinct from the flat, hard, overlapping scales of a reptile. Although some mammals, like the pangolin or the tail of a rat, do possess true epidermal scales, the typical body covering of a rabbit consists only of fur. Therefore, a rabbit is not characterized by the presence of epidermal scales on its main body surface.

The incorrect option is 4: Frog
The frog is an amphibian, belonging to the Class Amphibia. Amphibians are known for their moist, glandular, and highly permeable skin, which they often use for cutaneous respiration (breathing through the skin). To facilitate this gas exchange, the skin must remain moist and relatively thin. Consequently, adult frogs lack any protective external body scales, whether epidermal or dermal. The absence of a keratinized, scaly covering highlights the frog's dependence on moist environments and its transitional evolutionary position between aquatic and fully terrestrial vertebrates.