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[os-truh-koh-durm] /ˈɒs trə koʊˌdɜrm/
any of several extinct jawless fishes of the Ordovician, Silurian, and Devonian periods, having the body enclosed in an armor of bony plates.
1890-95; < New Latin Ostracodermi, plural ofOstracodermus < Greek ostrakódermos with a shell, equivalent to óstrako(n) shell, tile + -dermos -derm Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for ostracoderms


/ˈɒstrəkəˌdɜːm; ɒsˈtrækə-/
any extinct Palaeozoic fishlike jawless vertebrate of the group Ostracodermi, characterized by a heavily armoured body
Word Origin
C19: via New Latin from Greek ostrakon shell + -derm
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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ostracoderms in Science
Any of three orders of small, extinct primitive jawless fishes of the Ordovician through the Devonian Period. Most ostracoderms had their heads or entire bodies encased in fused bony plates. Some or all ostracoderms are sometimes classified together with the modern cyclostomes (lampreys and hagfish).
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for ostracoderms


an archaic and informal term for a member of the group of armoured, jawless, fishlike vertebrates that emerged during the early part of the Paleozoic Era (542-251 million years ago). Ostracoderms include both extinct groups, such as the heterostracans and osteostracans, and living forms, such as hagfishes and lampreys.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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