placoid

Placoid scales are found on cartilaginous fish including sharks.

Sharks are entirely covered by placoid scales.

Placoid scales are found in the cartilaginous fishes: sharks, rays, and chimaeras.

Bony fish have no placoid scales.

Their skin is smooth and largely covered by placoid scales, and their color can range from black to brownish gray.

Placoid scales cannot grow in size, but rather more scales are added as the fish increases in size.

Sharks and other chondrichthyes have placoid scales made of denticles, like small versions of their teeth.

Chondrichthyes have toothlike scales called dermal denticles or placoid scales.

There are yellow-white placoid lesions in the posterior pole at the level of the RPE.

Placoid scales, also called dermal denticles, are similar to teeth in that they are made of dentin covered by enamel.

Cosmoid scales are found in several ancient lobe-finned fishes, including some of the earliest lungfishes, and were probably derived from a fusion of placoid scales.

Such skins are naturally covered with round, closely set, calcified papillae called placoid scales, whose size is chiefly dependent on the age and size of the animal.

Acute posterior multifocal placoid pigment epitheliopathy (APMPPE)

Acute posterior multifocal placoid pigment epitheliopathy (APMPPE) primarily occurs in adults (with a mean age of 27).

Members of the elasmobranchii subclass have no swim bladders, five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins, and small placoid scales.

Many groups of bony fishes, including pipefishes and seahorses, several families of catfishes, sticklebacks, and poachers, have developed external bony plates, structurally resembling placoid scales, as protective armour.

However, sharks do have scales, they are just placoid scales, which are denser and appear smooth if rubbed in one direction, in contrast to leptoid scales, ganoid scales, and cosmoid scales.

Other distinctive characteristics include a strongly keeled caudal peduncle, highly textured skin covered in placoid scales and a mucus layer, a pointed snout-distinctly hooked in younger specimens-and a lunate caudal fin.

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 principal types of scales are the cycloid scales of salmon and carp, the ctenoid scales of perch, the placoid scales of sharks and rays, the ganoid scales of sturgeons and gars.

Their tough skin is covered with dermal teeth (again with Holocephali as an exception as the teeth are lost in adults, only kept on the clasping organ seen on the front of the male's head), also called placoid scales or dermal denticles, making it feel like sandpaper.

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 of which sits on top of a rectangular basal plate that rests on the dermis.