Turtles have a prominent shield.
A scute is a shield-shaped bony plate or scale found on the skin of some reptiles, birds, and mammals. Although similar in appearance to scales, scales have different origins and properties. Some scientists speculate that the structures may provide clues to the early evolution of feathers, since many dinosaurs, considered relatives of birds, also had scutes.
Crocodiles have shields.
Reptiles with prominent scutes include crocodiles, crocodiles, and turtles. Crocodile and crocodile scutes are the ridged bony plates that form the animal’s tough skin, protecting it from predators and possibly helping regulate its temperature. These scales have a bony base and are known as osteoderms.
In tortoises and freshwater turtles, the entire shell, or upper shell, is a structure of fused scales. The plates running through the center of the shell along the column are called central plates. The subsequent rows of plates on each side of the spine are called the costal plates, and the outer plates are known as the marginal plates. The plastron or underside of the turtle’s shell is also made of scales.
The scutes are the bony ridges that make crocodile skin so tough.
Each shield forms on a lower layer of skin, the dermis, below the epidermis. It may contain bone at its base, in which case it is known as an osteoderm. The rest of the shield consists of a fibrous protein, also found in the horns, known as keratin. Unlike snakes and lizards that shed the entire outer layer of their skin, animals with these structures shed only the outer layer of keratin. Scales are distinguished from scales in that they develop in the epidermis rather than the dermis.
Birds and mammals, such as reptiles, may have scutes. In birds, they are dermal structures of the feet. Mammals such as armadillos and pangolins have plate-shaped osteoderms that form a layer of armor. As in crocodiles, the scales of mammals have a protective function.
Researchers investigating bird ancestry have used scutes as a possible clue to finding the origin of feathers. It has been theorized that feathers evolved from the scales of reptiles, but tests have revealed that feathers and scales are genetically and chemically different. Shields, on the other hand, may be more genetically linked to feathers. It is even possible that shields evolved from feathers and not the other way around.
Fossil discoveries indicated that many dinosaurs likely had feathers, and that the feathers themselves may be a more primitive feature than previously thought. If that’s true, it’s possible that birds and dinosaurs evolved from a common feathered ancestor. Some scientists speculate that the shield may have developed from a feather structure in an ancestral organism of this type.