Amphistium
| Amphistium | ||||||||||||
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Amphistium |
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| Temporal occurrence | ||||||||||||
| Ypresian to Lutetian ( Eocene ) | ||||||||||||
| 56 to 41.3 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Amphistium | ||||||||||||
| Agassiz , 1835 | ||||||||||||
Amphistium is a fossil genus from the order of the flatfish (Pleuronectiformes). Fossils of the genus were first found in the Monte Bolca fossil deposit near the Italian city of Verona , and later also in the Paris Basin .
features
Amphistium has a rounded-oval, laterally strongly flattened body and spiny rays in the dorsal and anal fin. The dorsal and anal fins extend in an arc over almost the entire length of the trunk. The latter has 21 to 22 soft rays. Their outer edge is convex . The caudal fin is long, undivided and rounded. The eyes are small, the muzzle pointed.
The orbital region of the skull is asymmetrical , one eye is shifted in the direction of the back line in adult animals, but has not yet crossed it. This can vary from individual to individual, both on the right and on the left side of the head. Amphistium presumably lived a predatory life.
Systematics
Amphistium was initially assigned to the mackerel-like (Scombroidei) by Agassiz , a subordination of the perch-like (Perciformes). This assignment was widely accepted as the deformation of the skull was believed to be postmortem deformation. It was not until 2002 that the American paleontologist Jack Sepkoski put Amphistium as a core group representative in the order of flatfish, after it was recognized that the asymmetry of the skull only occurs in larger animals and is always identical in specimens of the same size.
species
- Amphistium altum , Paris basin
- Amphistium paradoxum , Monte Bolca
literature
- Matt Friedmann: The evolutionary origin of flatfish asymmetry. Nature 454 (7201), 2008, pp. 209-212 doi : 10.1038 / nature07108 .
- Karl Albert Frickhinger: Fossils Atlas Fishes. Mergus-Verlag, Melle, 1999, ISBN 3-88244-018-X .
