Cosmoid Scale

cosmoid scale

[′käz‚mȯid ′skāl]

(vertebrate zoology)

A structure in the skin of primitive rhipidistians and dipnoans that is composed of enamel, a dentine layer (cosmine), and laminated bone.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Cosmoid Scale

 

a scale of primitive Crossopterygii and Dipnoi fishes whose external surface is formed of a layer of cosmine (hence the name)—a continuous “parquet” pattern of tightly joined cutaneous teeth. The cosmoid scale is covered on top by a hard enamel-like dentin, which imparts its characteristic sheen. The cosmine is lined with a layer of spongy bone; at the base of the cosmoid scale lies a large layer of lamellar bone— isopedin. In the evolution of the Crossopterygii and Dipnoi, the external and spongy layers of the cosmoid scale gradually were reduced. A few isolated nodules of dentin have been preserved on the surface of the scale of the modern crossopterygian Latimeria.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.