Cheirolepis
| Cheirolepis | ||||||||||||
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Cheirolepis trailli |
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| Temporal occurrence | ||||||||||||
| Middle Devonian | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Cheirolepidae | ||||||||||||
| Pander , 1860 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Cheirolepis | ||||||||||||
| Agassiz , 1835 |
Cheirolepis is a bone fish from the Middle Devonian . The first fossil remains of this genus were found in the Old Red sandstone in Scotland, with other fossils from Canada. Cheirolepis is the first well known ray fins and is probably the primitive sister group of all other known ray fins. Earlier members of the class are only passed down from the late Silurian in the form of individual scales.
features
Cheirolepis was about 25 centimeters long. His body was slender and covered in small, rhombic, overlapping scales. The scales ran in curved diagonal rows diagonally back and down. They consisted of bone, dentin and an enamel- like substance on the outside ( ganoid scales ). The caudal fin was clearly heterocercial , but the lower caudal fin lobe was enlarged. The upper edge of the tail was reinforced by enlarged keel scales. The dorsal and anal fins were large and triangular.
The skull was large and heavy, the skull and roof of the mouth were ossified. The skull was encased in thin dermal bones . The large eye sockets are far in front. The mouth was large and had irregularly spaced pointed teeth. The jaw margins are formed by the maxillary and intermaxillary bone (premaxillary) in the upper jaw and dentals in the lower jaw, bones that are the most important tooth-bearing bones in all later vertebrates. The rear edge of the skull is connected to the gill region and the shoulder girdle . Since the skull was very mobile , the jaws could be opened very wide.
Way of life
Cheirolepis was a predatory fish that could swim fast and likely orientated itself with its eyes when catching prey. The large, very mobile jaw allowed it to eat prey that was 2/3 of its own body length. In the stomach region of Cheirolepis , remains of spiny sharks (Acanthodii) and the lungfish Dipterus have been found. Possibly they also ate small placodermi which they could not bite with their sharp teeth, but which they could crush with blunt palatal teeth .
literature
- Michael J. Benton : Paleontology of the vertebrates. Translation of the 3rd English edition. Pfeil, Munich 2007, ISBN 978-3-89937-072-0 .
- Joseph S. Nelson : Fishes of the World. 4th edition. John Wiley & Sons, Hoboken NJ 2006, ISBN 0-471-25031-7 .
- John A. Long: The Rise of Fishes. 500 Million Years of Evolution. The Johns Hopkins University Press, Baltimore MD et al. 1995, ISBN 0-8018-4992-6 .
Web links
- Palæos Cheirolepis