Dermal denticles literally mean “tiny skin teeth.” They are the minuscule scales found on elasmobranch species, such as sharks. Dermal denticles are often referred to as placoid scales. These scales serve many purposes, such as protection from predators and drag reduction in the water.
Dermal denticles are a very unique feature. They provide chain mail armor to the shark. The scales are made of apatite, a crystalline mineral, surrounded by collagen. This makes them especially durable, because they are very hard in the center and are surrounded by a flexible material. The scales are arranged in a helical pattern around the shark, leaving its body space to bend in the places it needs to. With shields stronger than steel covering its whole body, it is very difficult to injure a shark.
Different shark species have various scale shapes. The species shown above is a tiger shark, Galeocerdo cuvier, whose scales are shaped like a spades. Common to all species is the general form of the scale. Dermal denticles typically have three longitudinal ridges to reduce drag through the water. Evolution has created a concept in sharks we have been working on for years. Their structure cuts through the water like the front of a modern boat, only more efficient. Also, with so many scales slicing through the water, sharks are incredibly hydrodynamic.
Sharks’ dermal denticles are essentially perfected. They have evolved for millions of years. Sharks’ teeth even evolved from the dermal denticles, so the placoid scales are as conducive as possible. They provide everything an open water hunter needs: protection and hydrodynamics.
