placoderm
(plăkˈə-dûrmˌ)
noun Any of various extinct fishes of the Silurian and Devonian periods, characterized by bony plates of armor covering the head and flanks, hinged jaws, and paired fins.
Origin:
Origin: New Latin Placodermī, class name
Origin: : Greek plax, plak-, flat stone, plate; see plāk-1 in Indo-European roots
Origin: + -derm
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