placoid

[plak-oid]

adjective

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

Historical Examples of placoid

The Thornback Skate is covered with prickles (placoid scales).
Stories of the Universe: Animal Life
B. Lindsay
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.
Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 3
Various
In the Selachians the bony skeleton is restricted to the placoid elements.
Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 3
Various

British Dictionary definitions for placoid

placoid

adjective

platelike or flattened
(of the scales of sharks and other elasmobranchs) toothlike; composed of dentine with an enamel tip and basal pulp cavity

Word Origin for placoid

C19: from Greek plac-, plax flat

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012