placoderms

/P L EY1 K AH0 D ER0 M Z/
noun
  1. 1

    A member of an extinct class (Placodermi) of jawed fish with armored heads and thoraces; the group lived during the Silurian and Devonian periods.

Source: https://en.wiktionary.org/wiki/placoderm, https://en.wiktionary.org/wiki/placoderms