Ganoid scale

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Ganoid scales of a fossil bone organoid
Fossil melt scale fish

The ganoid scale ( ancient Greek γάνος ganos "shine, jewelry, enamel") or enamel scale is a type of scale that is only recently found in a few species of primitive bony fish - cartilaginous organoids , bone organoids and pike-pike . In the evolution of the other bony fish, the ganoid scale was subject to a strong reduction. In the older paleontological literature , fossil forms with this type of scale are often assigned the collective names “ganoids”, “ganoid fish” or “melt scales”, albeit with different delimitations .

Construction and ancestral origin

Ganoid scales are rhombic in shape and consist of a bony base that is coated with a pearlescent layer of ganoin - an enamel- like substance that is formed in the dermis . This is followed by a layer of dentine in some species (e.g. Senegalese pike ( Polypterus senegalus )). The bottom layer is a flat lamellar bone (a layer of isopedin and a bone base). In tribal history, the ganoid scales can be derived from scale forms of fossil species that contain a greater dentin content and less ganoin. The ganoid scale developed from the common ancestor like the cosmoid scale , which can only be found among the more recent species in the coelacanth . The best known fossil Ganoidschupper in Germany is Palaeoniscum freilebeni , Blainville , 1818. It was the most common fish in the North German Zechstein Sea and was found in many specimens in copper shale during mining in the southern Harz and in the Mansfeld Mulde.

See also

swell

  • Manfred Klinkhardt: Ganoid scale. In: Claus Schaefer, Torsten Schröer (Hrsg.): The large lexicon of aquaristics. 2 volumes. Eugen Ulmer, Stuttgart 2004, ISBN 3-8001-7497-9 , p. 398.
  • Harald Schliemann: integument and appendage organs. In: W. Westheide, R. Rieger: Special Zoology. Part 2: vertebrates or skulls . Spektrum Akademischer Verlag, Munich 2004, ISBN 3-8274-0307-3 , p. 21f.

Individual evidence

  1. ^ Ulrich Lehmann : Paleontological Dictionary . 4th edition. Ferdinand Enke Verlag, Stuttgart 1996, p. 93 .

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