placoid
Americanadjective
adjective
-
platelike or flattened
-
(of the scales of sharks and other elasmobranchs) toothlike; composed of dentine with an enamel tip and basal pulp cavity
Etymology
Origin of placoid
1835–45; < Greek plak- (stem of pláx ) something flat, tablet + -oid
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Researchers in this study also revisited an analysis of fossilized placoid scales, or tiny tooth-like scales that cover sharks, from the megalodon.
From Salon • Mar. 10, 2025
Shark teeth likely evolved from the jagged scales that cover their skin, called placoid scales.
From Textbooks • Jan. 1, 2015
An important feature is the complete absence of all trace of the calcified placoid plates which are so characteristic of the Elasmobranchii.
From Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 8 "Cube" to "Daguerre, Louis" by Various
As to whether they represent the remnant of a once present system of epidermal scales, which may have preceded the coating of placoid elements in the evolution of the vertebrate, there is no evidence.
From Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 8 "Cube" to "Daguerre, Louis" by Various
The skin of the dog-fish is closely set with pointed tooth-like scales, the placoid scales, and these are continued over the lips into the mouth as teeth.
From Text Book of Biology, Part 1: Vertebrata by Wells, H. G. (Herbert George)
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
