Definition of ostracoderm in English:



  • An early jawless fossil fish of the Cambrian to Devonian periods, having a heavily armoured body.

    Class Agnatha: several orders

    • ‘Enamel, or enameloid tissue covering tubercles, was clearly described in Ordovician vertebrates such as the ostracoderms.’
    • ‘By the Middle Devonian the armoured jawless ostracoderms were in decline, and instead the jawed fish were undergoing a great evolutionary radiation in both the sea and in freshwater.’
    • ‘With their armored head shield and trunk shield composed of overlapping bony plates, the placoderms appear at first glance extremely similar to the ostracoderms (armoured jawless fish).’
    • ‘These were jawless, armored fish informally called ostracoderms, but more correctly placed in the taxon Pteraspidomorphi.’
    • ‘If lancelets and the fossil ostracoderms are considered out-groups to living craniates, then the brains of the earliest craniates must have been very small for their body size.’


Late 19th century: from modern Latin Ostracodermi (former taxonomic name), from Greek ostrakon ‘shell’ + derma ‘skin’.