What does placoid mean?

Definitions for placoid
ˈplæk ɔɪdpla·coid

This dictionary definitions page includes all the possible meanings, example usage and translations of the word placoid.

Princeton's WordNet

  1. placoid, platelikeadjective

    as the hard flattened scales of e.g. sharks


  1. placoidnoun

    Any fish having placoid scales, such as the sharks.

  2. placoidadjective

    platelike; having irregular, platelike, bony scales, often bearing spines; pertaining to the placoids.


  1. placoid

    A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as well as possible hydrodynamic advantages. The term scale derives from the Old French escale, meaning a shell pod or husk.Scales vary enormously in size, shape, structure, and extent, ranging from strong and rigid armour plates in fishes such as shrimpfishes and boxfishes, to microscopic or absent in fishes such as eels and anglerfishes. The morphology of a scale can be used to identify the species of fish it came from. Scales originated within the jawless ostracoderms, ancestors to all jawed fishes today. Most bony fishes are covered with the cycloid scales of salmon and carp, or the ctenoid scales of perch, or the ganoid scales of sturgeons and gars. Cartilaginous fishes (sharks and rays) are covered with placoid scales. Some species are covered instead by scutes, and others have no outer covering on part or all of the skin. Fish scales are part of the fish's integumentary system, and are produced from the mesoderm layer of the dermis, which distinguishes them from reptile scales. The same genes involved in tooth and hair development in mammals are also involved in scale development. The placoid scales of cartilaginous fishes are also called dermal denticles and are structurally homologous with vertebrate teeth. Most fish are also covered in a layer of mucus or slime which can protect against pathogens such as bacteria, fungi, and viruses, and reduce surface resistance when the fish swims.


  1. placoid

    Placoid refers to a specific type of scale found on cartilaginous fish such as sharks and rays. These scales, also known as dermal denticles, are small, tooth-like structures that cover the skin, providing protection and reducing friction when the fish swims. The term "placoid" can also refer to a pattern of development in certain invertebrates, where an outer hard part develops from an inner soft part.

Webster Dictionary

  1. Placoidadjective

    platelike; having irregular, platelike, bony scales, often bearing spines; pertaining to the placoids

  2. Placoidnoun

    any fish having placoid scales, as the sharks

  3. Placoidnoun

    one of the Placoides

  4. Etymology: [Gr. pla`x, plako`s, a tablet + -oid.]

Chambers 20th Century Dictionary

  1. Placoid

    plak′oid, adj. plate-like.—Placoid fishes, an order of fishes having placoid scales, irregular plates of hard bone, not imbricated, but placed near together in the skin. [Gr. plax, plakos, anything flat and broad, eidos, form.]

Anagrams for placoid »

  1. podical

  2. podalic

How to pronounce placoid?

How to say placoid in sign language?


  1. Chaldean Numerology

    The numerical value of placoid in Chaldean Numerology is: 9

  2. Pythagorean Numerology

    The numerical value of placoid in Pythagorean Numerology is: 6

Translations for placoid

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"placoid." Definitions.net. STANDS4 LLC, 2024. Web. 12 Jun 2024. <https://www.definitions.net/definition/placoid>.

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