ostracoderm

noun
os·​tra·​co·​derm | \ ˈä-strə-kō-ˌdərm How to pronounce ostracoderm (audio) , ä-ˈstra-kə- \

Definition of ostracoderm

: any of various primitive, extinct jawless fish (class Agnatha) of the Lower Paleozoic with a bony covering of plates or scales serving as a protective armor and which on the broad head usually form a bony shield of fused plates

Note: Distant relatives of the hagfish and lampreys, ostracoderms were typically less than 12 inches (30.5 centimeters) long. Unlike earlier vertebrates using the gills for both feeding and breathing, ostracoderms were the first known forms to use the gills exclusively for respiration.

First Known Use of ostracoderm

1890, in the meaning defined above

History and Etymology for ostracoderm

from the base of New Latin Ostracodermi, subclass name, after earlier Ostracoderma, barnacle family, both formed from adaptations of Greek ostrakódermos "with a shell like a potsherd, hard-shelled," from óstrakon "earthen pot, potsherd, hard shell of a mollusk or tortoise" + -o- -o- + -dermos "having skin (of the kind specified)," adjective derivative of dermat-, dérma "skin" — more at ostracon, derm-

Keep scrolling for more

Learn More about ostracoderm

Time Traveler for ostracoderm

Time Traveler

The first known use of ostracoderm was in 1890

See more words from the same year

Statistics for ostracoderm

Cite this Entry

“Ostracoderm.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/ostracoderm. Accessed 23 Jan. 2021.

More from Merriam-Webster on ostracoderm

Britannica.com: Encyclopedia article about ostracoderm

Comments on ostracoderm

What made you want to look up ostracoderm? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

Test Your Vocabulary

Slippery Words Quiz—Changing with the Times

  • ducreux self portrait yawning
  • What is an earlier meaning of nice?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

TAKE THE QUIZ
 AlphaBear 2

Spell words. Make bears.

TAKE THE QUIZ
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!