scutes

Scute refers to a hard plate that forms part of the external armor in some animals. The term comes from the Latin scutum, meaning shield. Scutes can be made of keratinized skin (epidermal) or of dermal bone, depending on the lineage and species.

In turtles and tortoises, the shell is built from underlying bones covered by keratin-rich scutes. On the carapace (the top), scutes are arranged in recognizable rows and types, such as vertebral and costal scutes, with additional marginal scutes around the edge. The plastron (the bottom) typically carries scutes in patterns such as gular, pectoral, abdominal, femoral, and anal. Scutes grow as the animal matures and are commonly used in species identification; damage to a scute may not immediately compromise the underlying bones.

Crocodilians have a different arrangement: the back and tail bear large bony plates called osteoderms embedded in the skin, forming scute-like armor. These scutes provide protection and can influence thermoregulation due to their vascularized structure.

In some fishes, notably sturgeons and paddlefish, rows of bony scutes run along the body, offering protection along the flanks and adding to the animal’s exterior texture.

Overall, scutes are hard exterior plates found in various vertebrates. They serve protective, diagnostic, and sometimes hydrodynamic or thermoregulatory roles, and they may be keratinous or bony depending on the species.