Acanthodiformes
| Acanthodiformes | ||||||||||||
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Acanthodes bronni |
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| Temporal occurrence | ||||||||||||
| Unterdevon to Unterperm | ||||||||||||
| Locations | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Acanthodiformes | ||||||||||||
| Berg , 1940 |
The Acanthodiformes are a group of extinct fish from the Upper Paleozoic . Their fossil tradition begins in layers of the Lower Devonian and extends to the Lower Permian . After that, they probably died out due to increasing competition from bony fish.
features
The Acanthodiformes were the most successful group of "spiny sharks" and can be distinguished from the other two orders by the lack of the first dorsal fin, the toothless mouths and the well-developed gill trap with long trap extensions and an elongated gill region. The upper jaw ( palatoquadratum ) could be moved far to the side, which greatly enlarged the mouth opening. These characteristics suggest a free-swimming lifestyle and a filter feeder diet . A major trend in their evolution was the development of greater mobility in their pectoral fins. In addition, several ossified elements were created in the shoulder girdle. Dermal bones were missing.
The Acanthodiformes lacked additional fin spines between the pectoral and pelvic fins, with the exception of the early Devonian form Mesacanthus , which had a pair of such fin spines.
Systematics
The Acanthodiformes are counted among the Acanthodii , also called "Stachelhaie" in German. They are probably the sister group of the Ischnacanthiformes and together with these the sister group of the bony fish (Osteichthyes), or they must be placed in the parent group of the bony fish.
literature
- Robert L. Carroll : Paleontology and Evolution of the Vertebrates , Thieme, Stuttgart (1993), ISBN 3-13774-401-6 .
- John A. Long: The Rise of Fishes . The Johns Hopkins University Press, 1995, ISBN 0801849926 .
- Joseph S. Nelson : Fishes of the World . John Wiley & Sons, 2006, ISBN 0-471-25031-7 .
Individual evidence
- ^ Samuel P. Davis, John A. Finarelli & Michael I. Coates: Acanthodes and shark-like conditions in the last common ancestor of modern gnathostomes. Nature 486, 247-250, (14 June 2012) doi : 10.1038 / nature11080
- ↑ Brazeau, MD 2009. The braincase and jaws of a Devonian 'acanthodian' and the origin of modern gnathostomes. Nature Vol. 457 | 15 January 2009 | doi : 10.1038 / nature07436
