[ plak-uh-durm ]
/ ˈplæk əˌdɜrm /
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any of various extinct jawed fishes of the class Placodermi, dominant in seas and rivers during the Devonian Period and characterized by bony armored plates on the head and upper trunk.



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Origin of placoderm

1855–60; <New Latin Placodermi name of the class, plural of placodermus, equivalent to placo- (<Greek; see placoid, -o-) + -dermus-derm

Words nearby placoderm

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021

Example sentences from the Web for placoderm

British Dictionary definitions for placoderm

/ (ˈplækəˌdɜːm) /


any extinct bony-plated fishlike vertebrate of the class Placodermi, of Silurian to Permian times: thought to have been the earliest vertebrates with jaws

Word Origin for placoderm

C19: from Greek plac-, plax a flat plate + -derm
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

Scientific definitions for placoderm

[ plăkə-dûrm′ ]

Any of various extinct fishes of the class Placodermi of the Silurian and Devonian Periods, characterized by bony plates of armor covering the head and flanks. The bodies of placoderms were spindle-shaped or flattened, and their skeletons were usually partially bony and included a cranium. Placoderms were the first group of fish to evolve jaws, but are not closely related to the jawed fish of today.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.