placoderm

from WordNet (r) 3.0 (2006)

placoderm
    n 1: fish-like vertebrate with bony plates on head and upper
         body; dominant in seas and rivers during the Devonian;
         considered the earliest vertebrate with jaws

from The Collaborative International Dictionary of English v.0.48

Placoderm \Plac"o*derm\, n. [Gr. pla`x, plako`s, tablet + de`rma
   skin.] (Paleon.)
   One of the Placodermi.
   [1913 Webster]

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