Abstract
DURING the Triassic period the ganoid fishes with a gristly skeleton, belonging to the same grade as the existing sturgeons, were gradually replaced by ganoid fishes with a bony skeleton like the surviving Amia and Lepidosteus of North American fresh waters. Links between the two grades have already been recognized among Triassic fishes, and there can be no doubt that the one evolved from the other. The transition, however, evidently took place in the sea, and it has hitherto been studied chiefly when it was beginning (as in the Lower Trias of Spitsbergen, East Greenland, and Madagascar) and when it was almost completed (as in the Upper Trias and Rhætic of Italy and Austria). The ganoids of the Middle Trias—those of the critical period—are still well known only by freshwater forms from Australia and South Africa; and it must be noted that from early geological times onwards fresh waters have always been retreats for life which is no longer in the forefront of progress.
The Triassic Fishes of Besano, Lombardy
By James Brough. Pp. ix + 117 + 7 plates. (London: British Museum (Natural History), 1939). 20s.
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WOODWARD, A. The Triassic Fishes of Besano, Lombardy. Nature 144, 615 (1939). https://doi.org/10.1038/144615a0
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DOI: https://doi.org/10.1038/144615a0