plac·​o·​derm ˈpla-kə-ˌdərm How to pronounce placoderm (audio)
: any of a class (Placodermi) of extinct chiefly Devonian fishes with an armor of bony plates and primitive jaw structures

Examples of placoderm in a Sentence

Recent Examples on the Web Dunkleosteus, a genus from a class of armored fish called the placoderms, reached greater dimensions and could have easily preyed on early chondrichthyans. Joshua Rapp Learn, Discover Magazine, 1 Apr. 2023 Entelgnathus primordialis was an eight-inch-long placoderm — a kind of armored fish — and lived in seas that covered China 419 million years ago. Gemma Tarlach, Discover Magazine, 25 Sep. 2013 The arthrodire placoderm fossil from the Gogo Formation in Australia where the 380 million-year-old mineralized heart was discovered. Jennifer Ouellette, Ars Technica, 21 Sep. 2022 Enlarge / Reconstruction of a Devonian arthrodire placoderm. Jennifer Ouellette, Ars Technica, 21 Sep. 2022 Trinajstic and her team had previously discovered mineralized muscle tissue in these same placoderm fossils. Stephanie Pappas, Scientific American, 15 Sep. 2022 From one layer to the next one above, no more trilobites or nightmarish placoderms or dimetrodons—entire animal reigns and ecosystems have vanished. Manu Saadia, Ars Technica, 4 Sep. 2017 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'placoderm.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


New Latin Placodermi, ultimately from Greek plak-, plax + derma skin — more at derm-

First Known Use

circa 1859, in the meaning defined above

Time Traveler
The first known use of placoderm was circa 1859

Dictionary Entries Near placoderm

Cite this Entry

“Placoderm.” Dictionary, Merriam-Webster, Accessed 3 Dec. 2023.

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