<P> In most biological nomenclature, a scale (Greek λεπίς lepis, Latin squama) is a small rigid plate that grows out of an animal's skin to provide protection . In lepidopteran (butterfly and moth) species, 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 . </P> <P> Scales are generally classified as part of an organism's integumentary system . There are various types of scales according to shape and to class of animal . </P> <P> Fish scales are dermally derived, specifically in the mesoderm . This fact distinguishes them from reptile scales paleontologically . Genetically, the same genes involved in tooth and hair development in mammals are also involved in scale development . </P> <P> True cosmoid scales can only be found on the Sarcopterygians . The inner layer of the scale is made of lamellar bone . On top of this lies a layer of spongy or vascular bone and then a layer of dentine - like material called cosmine . The upper surface is keratin . The coelacanth has modified cosmoid scales that lack cosmine and are thinner than true cosmoid scales . </P>

Differences in the scales of fishes and reptiles lies in their being