Gryphaea
| Gryphaea | ||||||||||||
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Gryphaea (fossil) |
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| Temporal occurrence | ||||||||||||
| Triassic to Jurassic | ||||||||||||
| 208 to 135 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Gryphaea | ||||||||||||
| Lamarck , 1801 | ||||||||||||
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Gryphaea is an extinct genus of mussels that was related to oysters . Their fossil shells are mainly found in the layers of the Jurassic (from around 200 million years ago to 135 million years ago).
features
Its housing is characterized by a very strongly curved left flap, which is closed by the flat right flap like a lid. The mussel shells are very thick-walled. Gryphaea is a dysodontic clam, so it has no teeth on its lock. Relatives of the genus Gryphaea from the family Gryphaeidae are still common in the oceans today.
Way of life
Gryphaea fossils are found in large quantities at specific sites . This suggests that it formed colonies. She lived on the bottom of shallow seas . The curved, left shell was buried in the substrate of the ocean floor, while the flat "lid" opened and allowed the mussel to filter food. Therefore, fossil collectors often refer to the left shell as the "lower" and the right as the "upper".
evolution
The Gryphaea species from the strata of the Lower Jurassic show a steady increase in size up to the Middle Jurassic. This increase in size is not due to a longer life expectancy and thus a higher age of later forms and species, but to greater growth rates. Accelerated growth is accompanied by characteristics of heterochrony (pedomorphosis).
Types (selection)
- Gryphaea arcuata , 6 cm, is found frequently in Germany and France, the key fossil in the Sinemurium
- Gryphaea dilobotes , up to 14 cm, Western Europe, key fossil for the Callovium
- Gryphaea gigantea , 10 - 12 cm, is found in Western Europe in calcareous-marly facies, a key fossil for the Pliensbachian
literature
- Douglas S. Jones, Stephen Jay Gould: Direct Measurement of Age in Fossil Gryphaea: The Solution to a Classic Problem in Heterochrony . Paleobiology, Vol. 25, No. 2, pp. 158-187, 1999.
