ostracostean (ostrakostean)

and n. I. a. Pertaining to the Ostracostei, or having their characters; placoderm. II. n. A fish of the group Ostracostei ; a pla coderm. Ostracostei (os-tra-kos'tē-i), n. pl. [NL., pl. of ostracosteus: see ostracosteous.] A group of extinct placoganoid fishes having the head and generally the anterior part of the trunk incased in a strong composed of many large ga noid plates immovably joined to one another Also called Placoderm at a. ostracosteous (os-tra-kos'tē-us), a. [