Turtles have a prominent scute.
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, as many dinosaurs, widely considered to be relatives of birds, also had shields.
Crocodiles have shields.
Reptiles with prominent shields include crocodiles, crocodiles, and turtles. Scutes in crocodiles and crocodiles are the bony, striated plates that make up the animal’s tough skin, protecting it from predators and possibly helping it regulate its temperature. These scales have a bony base and are known as osteoderms.
In tortoises and tortoises, the entire carapace, or upper shell, is a structure of fused scales. The plates that run through the center of the shell along the column are called center plates. The next rows of plates on each side of the column are called costal plates and the outer plates are known as marginal plates. The plastron or underside of the turtle’s shell is also made of scales.
Scutes are the bony ridges that make crocodile skin so tough.
Each scute forms in a lower layer of skin, the dermis, under the epidermis. It may contain bone at its base, in which case it is known as osteoderm. The rest of the scute consists of a fibrous protein, also found in 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, like reptiles, can have shields. In birds, they are dermal structures of the feet. Mammals like armadillos and pangolins have plate-shaped osteoderms that form an armor layer. As in crocodilians, scales in mammals have a protective function.
Researchers investigating the ancestry of birds have used shields as a possible clue to finding the origin of feathers. It has been theorized that feathers evolved from reptilian scales, but tests have revealed that feathers and scales are genetically and chemically different. Scutes, on the other hand, may be genetically more closely linked to feathers. It’s even possible that scutes evolved from feathers rather than vice versa.
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 feathered common ancestor. Some scientists speculate that the scute may have developed from a feather structure in an ancestral organism of this type.