Dermal Denticles
Dermal denticles are small, hard, tooth-like structures, also called placoid scales. They have the same structure as a tooth, having an outer layer of enamel, dentine and a central pulp cavity. Sharks' teeth and skin are composed of this type of scale.

Dogfish
Dogfish are the most common shark. They congregate in schools and migrate. They range in size from tiny to enormous and are found worldwide.

Dusky Shark
The Dusky Shark (Carcharhinus obscurus) is a requiem shark that is also known as the bay shark, the shovelnose, the lazy-gray, and the black whaler. It is charcoal colored on top and white with copper-colored markings below. It has a faint pale stripe along its sides. Dusky sharks average about 10 ft (310 cm) long; females are slightly larger than males. The largest one found was about 13 ft (4 m) long. It lives at all levels of the ocean and from the shoreline to out at sea. It is found in warm temperate and tropical waters worldwide. It migrates to cooler waters during warm weather, probably for reproduction and feeding. This shark is often seen following ships and is hunted as a game fish. Overfishing is diminishing the numbers of this shark. Few Dusky shark attacks are documented, but it is considered dangerous. It normally eats small fish (like sardines), large fish (like tuna), flatfish, other sharks, and eels. Females are mature when they are 9 ft (2.8 m) long and have litters of about 10 pups which are roughly 3 ft (95 cm) long each. There is a 16 month gestation period. Classification: Order Carcharhiniformes, Family Carcharhinidae (requiem sharks), Genus Carcharhinus, Species obscurus.



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