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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How to use placoderm in a sentence
The site is teeming with toothy, bony fishes, particularly armored placoderms, but bears just one chondrichthyan.Ancient fish fossils highlight the strangeness of our vertebrate ancestors | Carolyn Gramling | September 28, 2022 | Science News
placoderm, plak′o-dėrm, adj. noting an order of fossil fishes having their skin covered with bony plates.
British Dictionary definitions for placoderm
any extinct bony-plated fishlike vertebrate of the class Placodermi, of Silurian to Permian times: thought to have been the earliest vertebrates with jaws
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
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.
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