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A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as well as possible hydrodynamic advantages.
Derived from placoid scales, they have a thick coat of enamel, but without the underlying layer of dentin. These scales cover the fish's body with little overlapping. They are typical of gar and bichirs. Cycloid scales are small, oval-shaped scales with growth rings like the rings of a tree. They lack enamel, dentin, and a vascular bone layer.
Tentative studies appear to suggest that the fish possessed a more developed braincase than the lampreys, with an almost shark-like outline. Internal scales have also been recovered, some fused into plates resembling gnathostome tooth-whorls to such a degree that some researchers favour a close link between the families. [11]
Keeled scales of a colubrid snake (banded water snake; Nerodia fasciata). 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.
The scales are small. As with many deep-living fish, the lateral line system in grenadiers is well-developed; it is further aided by numerous chemoreceptors located on the head and lips and chemosensory barbels underneath the chin. Benthic species have swim bladders with unique muscles attached to them. The animals are thought to use these ...
Cosmine was first described in the Osteolepiform Megalichthys hibberti by Williamson in 1849, in a purely descriptive, pre-Darwinian, non-evolutionary framework. [4] Goodrich [5] expanded on Williamson's descriptions, hypothesizing a transition from a monoodontode scale (like a chondryicthian placoid scale) to a complex polyodontode scale through fusion of discrete units.
Skates belong to the ancient lineage of cartilaginous fishes. Fossil denticles (tooth-like scales in the skin) resembling those of today's chondrichthyans date at least as far back as the Ordovician, with the oldest unambiguous fossils of cartilaginous fish dating from the middle Devonian.
Aristotle (ca. 340 B.C.) may have been the first scientist to speculate on the use of hard parts of fishes to determine age, stating in Historica Animalium that “the age of a scaly fish may be told by the size and hardness of its scales.” [4] However, it was not until the development of the microscope that more detailed studies were performed on the structure of scales. [5]