Symmoriidae
| Symmoriidae | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Upper Devon to Lower Carbon | ||||||||||||
| 382.7 to 323.2 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Symmoriidae | ||||||||||||
| Dean , 1909 |
The Symmoriidae are an extinct family of shark-like cartilaginous fish from the Symmoriida group . The taxon was first established by Bashford Dean in 1909. The eponymous genus forms Symmorium ; two other genera are Cobelodus and Denaea . Fossils were found on the American double continent as well as in Europe and are dated to the Upper Devonian and Lower Carboniferous .
features
The genera of the Symmoriidae are physically similar to the Cladoselache , another primitive genus of the slab gill, but outside of the Symmoriida. They had an extension of the pectoral fin called the metapterygial axis. The function is still being discussed, presumably it was used for locomotion, defense or courtship . Furthermore, an outgrowth over the shoulder region, which occurs in other families of Symmoriida, was not present.
Systematics
The Symmoriidae are the eponymous and at the same time most basic family of the Symmoriida. The sister taxon probably forms an unnamed group that includes the genus Falcatus and the Stethacanthidae .
| Symmoriida |
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Genera
literature
- Michael J. Benton : Paleontology of the vertebrates. 2007, ISBN 3-89937-072-4