Definition of ganoid in US English:



  • 1(of fish scales) hard and bony with a shiny surface that resembles enamel.

    Compare with ctenoid and placoid
    • ‘Gar species in North America are easily recognized by their long snouts, sharply toothed jaws, non-overlapping and diamond shaped ganoid scales, and posterior placement of dorsal and anal fins on the body.’
    • ‘They also possess a heterocercal caudal fin and remnants of ganoid scales; both are uncommon among extant actinopterygians.’
    • ‘Actinopterygians may have ganoid, cycloid, or ctenoid scales, or no scales at all in many groups.’
    • ‘The actinopterygians quickly jettisoned their ganoid scales and thus dispensed with the need for most endochondral bone.’
    • ‘This species has specialized scales, which are called ganoid scales, and it has nostrils or nares on tentacles that protrude from the head.’
    1. 1.1 (of a fish) having ganoid scales.
      • ‘The purpose of this research is to study ganoid fish taphonomy, specifically, how each type of fish decomposes, including anatomical location and extent of postmortem damage, and possibly, its cause.’


  • A primitive fish that has ganoid scales, e.g. a sturgeon or freshwater garfish.

    • ‘In the collection of ganoids the most complete is representation of Acipenseriformes, mainly of acipenserids proper.’
    • ‘I tried to follow his scheme of division into the order of ctenoids and ganoids, with the result that I found one of my species of side-swimmers had cycloid scales on one side and ctenoid on the other.’
    • ‘The ganoids had already reached their evolutionary climax in the Permian and Triassic, some 270-190 million years ago; today they are few in number when compared with the dominant bony fishes.’
    • ‘In the ganoids the upper lobe of the tail fin is the largest.’
    • ‘Bony fishes, lungfishes, & most ganoids - retain highly cartilaginous neurocranium that is covered by membrane bone’


Mid 19th century: from French ganoïde, from Greek ganos ‘brightness’.