- platelike, as the scales or dermal investments of sharks.
Origin of placoid
1835–45; < Greek plak- (stem of pláx) something flat, tablet + -oid
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for placoid
The Thornback Skate is covered with prickles (placoid scales).Stories of the Universe: Animal Life
The teeth of Selachii are fundamentally identical with placoid scales.The Vertebrate Skeleton
Sidney H. Reynolds
The most primitive form of the first type of dermal structures is that of the placoid scales of Elasmobranchii.The Works of Francis Maitland Balfour, Volume III (of 4)
Francis Maitland Balfour
In the groups of fishes above the Selachians, the coating of placoid elements shows various modifications.
In the Selachians the bony skeleton is restricted to the placoid elements.
- platelike or flattened
- (of the scales of sharks and other elasmobranchs) toothlike; composed of dentine with an enamel tip and basal pulp cavity
C19: from Greek plac-, plax flat