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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 ...
The nursehound (Scyliorhinus stellaris), also known as the large-spotted dogfish, greater spotted dogfish or bull huss, is a species of catshark, belonging to the family Scyliorhinidae, found in the northeastern Atlantic Ocean. It is generally found among rocks or algae at a depth of 20–60 m (66–197 ft).
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.
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 ...
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
Scyliorhinidae is a family of sharks, one of a few families whose members share the common name catsharks, belonging to the order Carcharhiniformes, the ground sharks. Although they are generally known as catsharks, some species can also be called dogfish due to previous naming. [ 2 ]
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.
In California, this shark is usually found in shallow waters that are less than 12 meters (39 ft 4 in) deep, but it has been found to a maximum depth of 67 meters (219 ft 10 in). In the Gulf of California, the majority of gray smooth-hounds are found less than 80 meters (262 ft 6 in) deep but have been found up to 265 meters (869 ft 5 in) below ...