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Existing fish groups featuring ganoin are bichirs and gars, but ganoin is also characteristic of several extinct taxa. [4] It is a characteristic component of ganoid scales . Ganoine is an ancient feature of ray-finned fishes, being found for example on the scales of stem group actinopteryigian Cheirolepis . [ 4 ]
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.
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.
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]
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.
Bowfin heads are smooth and free of scales, whereas the northern snakehead has scales that uniformly continue from their body through to their head. [32] The burbot (Lota lota), a predatory fish native to streams and lakes of North America and Eurasia, is also commonly mistaken for bowfin. Burbots can be distinguished by their flat head and ...
Scales to be domed; Dorsal fin to be single, all other fins to be paired; Caudal fin to be divided and forked and held above the horizontal; Extremities of fins to have a slightly rounded appearance; Minimum length of body to be 5.5 cm (2¼ inches) The fish should be bright and alert and displaying well developed domed scales all over the body ...
Some fish, such as pineconefish, are completely or partially covered in large armored scales commonly termed scutes. [1] Many Clupeomorpha have an abdominal row of scutes, which are scales with raised, sharp points that are used for protection, and in some cases they also possess dorsal scutes anterior to the dorsal fin, as in Knightia spp ...