• WordNet 3.6
    • n Heterostraci extinct group of armored jawless fishes or fish-like vertebrate; taxonomy is not clear
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Century Dictionary and Cyclopedia
    • heterostraci An order of ostracodermous fishes. They have an exoskeleton of shagreen, plates or scales without bone-cells, each plate consisting of three layers, and bodies without paired appendages. They are all of Paleozoic age.
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