PLACOIDEAN Meaning and
Definition
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Placoidean refers to a specific type of scales that are characteristic of cartilaginous fishes, such as sharks and rays. It is derived from the Greek word "plax" meaning plate or scale. Placoidean scales are unique among fishes and possess distinct structural features.
These scales have a flattened, disc-shaped structure, often resembling a small plate or tile. They are composed of an inner layer of dentin, a hard mineralized tissue, and an outer layer of enamel. The enamel layer forms a protective hardened surface, while the dentin provides flexibility and strength. This combination makes the placoidean scales highly efficient in protecting the fish's body from external abrasions, predators, and other environmental factors.
Additionally, placoidean scales are covered with tiny projections called dermal denticles. These denticles have a rough texture, pointing towards the rear of the fish's body. This unique feature helps to reduce drag by creating a hydrodynamic advantage, allowing the fish to swim swiftly through water.
Placoidean scales are often arranged in overlapping rows, providing a robust armor-like covering for the fish's body. Their presence not only contributes to the overall structural integrity of the fish, but also aids in reducing water turbulence and noise underwater.
Overall, the placoidean scales are one of the defining features of cartilaginous fishes, serving as an adaptation that enhances their survival and predatory capabilities in aquatic environments.
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• A term applied to an order of fishes characterised by having their skins covered irregularly with plates of enamel, either of considerable size or reduced to small points-this order includes skates, rays, dogfish, and sharks.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.
Common Misspellings for PLACOIDEAN
- placodian
- Plecoidian
- Placoydian
- Placoidien
- olacoidean
- llacoidean
- -lacoidean
- 0lacoidean
- pkacoidean
- ppacoidean
- poacoidean
- plzcoidean
- plscoidean
- plwcoidean
- plqcoidean
- plaxoidean
- plavoidean
- plafoidean
- pladoidean
- placiidean
Etymology of PLACOIDEAN
The word "placoidean" is derived from the Latin word "placoideus", which means "flat, plate-like". It is formed by combining the Latin prefix "placo-" meaning "flat" and the suffix "-idean" indicating a characteristic or relationship. This term is commonly used in biology to describe a type of denticle or scale found on the skin of some fish, particularly sharks and rays.
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