Scale (zoology)

In zoology, a scale (Ancient Greek: λεπίς, romanized: lepís; Latin: squāma) is a small rigid plate that grows out of an animal's skin to provide protection.

In lepidopterans (butterflies and moths), scales are plates on the surface of the insect wing, and provide coloration.

Scales are quite common and have evolved multiple times through convergent evolution, with varying structure and function.

They are arranged so as to overlap in a head-to-tail direction, like roof tiles, allowing a smoother flow of water over the body and therefore reducing drag.

[3] They come in two forms: Reptile scale types include: cycloid, granular (which appear bumpy), and keeled (which have a center ridge).

All reptilian scales have a dermal papilla underlying the epidermal part, and it is there that the osteoderms, if present, would be formed.

The green iguana possesses large feature scales on the ventral sides of its neck, and dorsal spines not supported by osteoderms.

Many extinct non-avian dinosaurs such as Carnotaurus and Brachylophosaurus are known to possess feature scales from skin impressions.

The scales and scutes of birds were thought to be homologous to those of reptiles,[4] but are now agreed to have evolved independently, being degenerate feathers.

They have been convergently evolved, being unrelated to mammals' distant reptile-like ancestors (since therapsids lost scales), except that they use a similar gene.

[9] Butterflies and moths - the order Lepidoptera (Greek "scale-winged") - have membranous wings covered in delicate, powdery scales, which are modified setae.