Definition of "placoderm" []

• 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. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Scientists from Australia and Britain studying 380million-year-old fossils of placoderm fish were initially confused when they realized that the two fish were carrying embryos."
• "Nature that presents this missing piece of the puzzle and completes the picture of placoderm reproduction from mating to birth."
• "The authors looked for a clasper in their placoderm fossils but couldn't find one, so they were forced to argue that it had been made of soft cartilage and had not been preserved."