ostracoderm
(ŏsˈtrə-kŏ-dûrmˌ)
noun Any of several groups of extinct primitive jawless fishes of the Ordovician through the Devonian periods in North America and Europe, having bodies that were encased in an armor of bony plates.
Origin:
Origin: Greek ostrakon, shell; see ost- in Indo-European roots
Origin: + -derm
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