placoid
Americanadjective
adjective
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platelike or flattened
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(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
A singular species, rare, but easily recognized by its peculiar, placoid scales, large and firmly embedded in the peridial wall.
From The North American Slime-Moulds A Descriptive List of All Species of Myxomycetes Hitherto Reported from the Continent of North America, with Notes on Some Extra-Limital Species by MacBride, Thomas H. (Thomas Huston)
Many years before, several observers—J. Müller, Williamson, and Steenstrup—had been struck with the resemblance existing between the placoid scales and the teeth of Elasmobranch fishes.
From Form and Function A Contribution to the History of Animal Morphology by E. S. (Edward Stuart) Russell
Besides the teeth there perhaps remain relics of the placoid scales in the anatomy of the higher vertebrata, in the membrane bones.
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.
