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Bony fish do not have placoid scales like cartilaginous fish, instead they consist of three types of scales that do not penetrate the epidermis in the process. The three categories of scales for Osteichthyes which are cosmoid scales, ganoid scales, teleost scales.
In bony fishes, the scales along the lateral line have central pores that allow water to contact the sensory cells. The dorsal fin spines of dogfish sharks and chimaeras, the stinging tail spines of stingrays, and the "saw" teeth of sawfishes and sawsharks are fused and modified placoid scales.
The bony fish lineage shows more derived anatomical traits, often with major evolutionary changes from the features of ancient fish. They have a bony skeleton, are generally laterally flattened, have five pairs of gills protected by an operculum, and a mouth at or near the tip of the snout. The dermis is covered with overlapping scales. Bony ...
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]
Leptoid scales are found on higher-order bony fish. As they grow they add concentric layers. As they grow they add concentric layers. 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 ]
Arowanas are freshwater bony fish of the subfamily Osteoglossinae, also known as bony tongues [1] (the latter name is now often reserved for Arapaiminae). [2] In this family of fish, the head is bony and the elongated body is covered by large, heavy scales, with a mosaic pattern of canals.
Actinopterygii (/ ˌ æ k t ɪ n ɒ p t ə ˈ r ɪ dʒ i aɪ /; from actino- 'having rays' and Ancient Greek πτέρυξ (ptérux) 'wing, fins'), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish [2] that comprise over 50% of living vertebrate species. [3]
They can be contrasted with the Osteichthyes or bony fish, which have skeletons primarily composed of bone tissue. Chondrichthyes are aquatic vertebrates with paired fins, paired nares, placoid scales, conus arteriosus in the heart, and a lack of opercula and swim bladders.