Definition of "placoderm"

placoderm

noun
plural placoderms
1. (paleontology) A member of an extinct class (Placodermi) of jawed fish with armored heads and thoraces; the group lived during the Silurian and Devonian periods.
  Quotations
  Out to sea are placoderms – heavily armoured fish, some of them more than six metres (twenty feet) long and equipped with massive, powerful jaws.
  2012, Caspar Henderson, The Book of Barely Imagined Beings, Granta Books, published 2013, page 12
adjective
comparative more placoderm, superlative most placoderm
1. (paleontology) Pertaining to the class Placodermi.
  Quotations
  Research published recently on placoderm fish fossils from Scottish Devonian lakes (around 365 myo) found evidence for how this extinct group of animals copulated.
  2018 January 24, Elsa Panciroli, The Guardian