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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
There are numerous species of sharks found in the Pacific Ocean; of these sharks, 36 [1] have habitat ranges throughout the coastlines and surrounding waters of California, as identified below. Identifications include common names; scientific names; the taxonomic rank, family; conservation statuses according to IUCN; and an image.
The Pacific spiny dogfish (Squalus suckleyi) is a common species of the Squalidae (dogfish) family of sharks and are among the most abundant species of sharks in the world. This species is closely related to the Spiny dogfish and for many years they were treated as a single species. [ 4 ]
Placoid (pointed, tooth-shaped) scales are found in the cartilaginous fishes: sharks, rays. They are also called dermal denticles . Placoid scales are structurally homologous with vertebrate teeth ("denticle" translates to "small tooth"), having a central pulp cavity supplied with blood vessels , surrounded by a conical layer of dentine , all ...
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 ...
placoid scales Teeth-like scales found in sharks and rays. posterior Towards the hind end of the fish. postorbital Behind the eye. precaudal Anterior to the tail portion. premaxillaries Two bones forming the front portion of the upper jaw. preocular spine A spine positioned above and in front of the eye. preopercle, preoperculum
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 ...
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.