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Besides sharks, primitive skates, chimaeras and crossopterygians (’tassel-fins’), there are especially frequent finds of Aspidorhynchus.
This Weigert reproduction shows a member of the so-called ganoid fishes. 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.
The internal skeleton of the ganoid fishes, especially the vertebral column, is only lightly ossified. The massive scales covering the entire body are
usually rhomboidal with a glossy surface of ganoin. Aspidorhynchus had a long and beaked mouth. The bill-fish was an efficient swimmer and found an ideal hunting-ground in the Jurassic waters. The enclosing layers of sea-mud,
subjected to increasing pressure, dehydration and mineralisation, finally hardened into limestone, the skeleton embedded therein being compressed into a paperthin layer. Only 150 million years later was the fossil brought to
light by a quarry worker and fully exposed through the patience and skill of a preparator.
Original: Museum Bergér, Eichstätt, Germany
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