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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. Surgeonfish have a scalpel-like blade, which is a modified scale, on either side of the caudal peduncle. [56]
Placoid Scale. Super Smooth scales (dermal denticles) coat the skin of sharks, rays, and cartilaginous fishes due to the absence of dermal bone. These scales are present in the dermis, which has fibrous connective tissue components, and project through the epidermis, which contains secretory cells and stratified epidermal cells, to the surface.
The trunk and tail are laterally compressed, while the head region is dorsoventrally compressed. The entire body is covered by an exoskeleton of placoid scales. The mouth is located on the ventral side and is bound on both sides by jaws. It has two rows of homodont or polyphyodont teeth, which are homologous to the placoid scales covering
Placoid scales are found on cartilaginous fish including sharks and stingrays. These scales, also called denticles, are similar in structure to teeth, and have one median spine and two lateral spines. The modern jawed fish ancestors, the jawless ostracoderms and later jawed placoderms, may have had scales with the properties of both placoid and ...
Chondrichthyes (/ k ɒ n ˈ d r ɪ k θ i iː z /; from Ancient Greek χόνδρος (khóndros) 'cartilage' and ἰχθύς (ikhthús) 'fish') is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage.
Ganoid scales are flat, basal-looking scales. 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 ...
Dogfish sharks use their strong jaw and sharp teeth to consume their prey. The spiny dogfish has broken several records in the areas of migration and gestation. This shark tends to be a highly migratory species: one shark was recorded as travelling 8,000 km (5,000 miles) after being tagged in Washington state, United States, and found again ...
The spiny dogfish (Squalus acanthias), spurdog, mud shark, or piked dogfish [4] is one of the best known species of the Squalidae (dogfish) family of sharks, which is part of the Squaliformes order. [5] While these common names may apply to several species, Squalus acanthias is distinguished by two spines (one anterior to each dorsal fin) and ...