Epidermal scales are present in :

Question

Accepted Answer

The correct option is 3: Pigeon

Epidermal scales are horny, tough extensions of the stratum corneum, the outermost layer of the epidermis. These scales are primarily composed of keratin, a hard protein, and serve a protective function by reducing water loss and providing a physical barrier against abrasion. While the entire body of a bird, such as the **Pigeon** (Class Aves), is famously covered in feathers—which are themselves modified epidermal appendages—true, overlapping epidermal scales are characteristically present on the parts of the bird's body not covered by feathers. Specifically, these scales are clearly visible on the lower legs, the feet (tarsometatarsus and toes), and at the base of the bill. Their presence on the feet provides necessary protection against rough surfaces and environmental wear, confirming that the pigeon does possess epidermal scales.

The incorrect option is 1: Scoliodon

Scoliodon, commonly known as the dogfish, belongs to the Class Chondrichthyes (cartilaginous fishes). The body covering of Scoliodon consists of minute, hard, tooth-like structures called **placoid scales**, or dermal denticles. Placoid scales are fundamentally different from epidermal scales because they are *dermal* derivatives, meaning they originate from the mesoderm in the dermis, unlike epidermal scales which are strictly derived from the ectodermal epidermis. Placoid scales are structurally homologous to the vertebrate teeth, composed of dentine and covered with a hard, enamel-like substance called vitrodentine. Therefore, Scoliodon does not possess true epidermal scales.

The incorrect option is 2: Rabbit

The Rabbit belongs to the Class Mammalia. The definitive, characteristic body covering of mammals is **hair** or **fur**, which is a highly specialized epidermal derivative used primarily for insulation and sensory purposes. True epidermal scales are generally absent on the main trunk of a rabbit's body. Although epidermal scales may be present in a few localized areas in some mammals, such as the tail and paws of rodents, and are highly modified into structures like horns, claws, or nails, the presence of hair across the body is the overriding feature of the Rabbit's integumentary system, making it an incorrect answer.

The incorrect option is 4: Frog

The Frog is a representative of the Class Amphibia. Amphibians are distinguished by having a smooth, glandular, highly permeable, and **moist skin** that lacks any external protective scales, whether dermal or epidermal. This thin, moist skin is vital for the physiological process of **cutaneous respiration**, or breathing through the skin, which requires a highly vascularized and exposed surface. The general absence of keratinized scales is a key evolutionary feature distinguishing most modern amphibians from other vertebrates, as the scales would hinder gas exchange. Thus, the common frog does not have epidermal scales.