Osteolepiformes
| Osteolepiformes | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Skull of Platycephalichthys |
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| Temporal occurrence | ||||||||||||
| Middle Devon to Lower Perm | ||||||||||||
| 385 to 275 million years | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Osteolepiformes | ||||||||||||
| Berg , 1937 |
The osteolepiformes are an extinct group of bony fish from the class of the meat fin fish (Sarcopterygii). They lived from the Middle Devon to the Middle Permian and are of particular importance as they are close to the origin of the land vertebrates (Tetrapoda). One of them is Eusthenopteron , which is one of the best-studied fossil fish.
According to a recent cladistic analysis, the osteolepiformes do not form a natural group (clade, monophylum), as some families are more closely related to the tetrapods than others. The osteolepiformes therefore only represent a stage of development (English: grade ) between the still relatively fish-like meat fins and the already very tetrapod-like meat fins.
features
Her body, covered by thick, rhombic scales ( cosmoid scales ), was slim, the pectoral fins were relatively low on the trunk. The pectoral and ventral fins were short and rounded. The caudal fin can have been homo- or heterocercus (equilobed or uneven-lobed).
The skull as well as the dentition resemble those of the basal land vertebrates ( Acanthostega , Ichthyostega ). The osteolepiformes had developed an external nostril and a choane . The scapulocoracoid, part of the shoulder girdle, had a pit in which the (proximal) spherical end of the “ humerus ” of the pectoral fins pointing towards the trunk was very flexible (“tetrapod joint”).
Systematics
Traditionally, the osteolepiformes comprise the following families and genera:
- Canowindridae ( Beelarongia , Canowindra , Koharolepis ), restricted to eastern gondwana (Australia, Antarctica)
- Osteolepidae ( Osteolepis , Gryoptychus , Thursius ), less than 50 cm, two dorsal fins, heterocerke tail fin.
- Megalichthyidae
- Tristichopteridae (= Eusthenopteridae: Marsdenichthys , Eusthenopteron , Platycephalichthys )
- Rhizodopsidae
- Gogonasus ?
Individual evidence
- ^ Brian Swartz: A Marine Stem-Tetrapod from the Devonian of Western North America. PLoS ONE 7, 2012, doi : 10.1371 / journal.pone.0033683
literature
- Joseph S. Nelson : Fishes of the World. John Wiley & Sons, 2006, ISBN 0-471-25031-7 .
- Kurt Fiedler: Textbook of Special Zoology, Volume II, Part 2: Fish. Gustav Fischer, Jena 1991, ISBN 3-334-00339-6
- John A. Long: The Rise of Fishes . Johns Hopkins University Press , 1995, ISBN 0-8018-4992-6
- Hans-Peter Schultze: Fossile Sarcopterygii page 301. In: Wilfried Westheide, Reinhard Rieger: Special Zoology Part 2: Vertebrae and Skull Animals , 1st edition, Spectrum Academic Publishing House, Heidelberg / Berlin 2004, ISBN 3-8274-0307-3
Web links
- Osteolepiformes on Palæos