Gryphaea

Gryphaea ( fossil)

• Worldwide

• Gryphaea arcuata
• Gryphaea dilobotes
• Gryphaea gigantea

Gryphaea is an extinct genus shell that was related to the oysters. Their fossil shells are found mainly in the layers of the Law ( of around 200 million years ago to 135 million years ago ).

Features

Your case is characterized by a very strong bent left door, which is closed by the flat right valve as with a lid. The shells are very thick-walled. Gryphaea is one of the dysodonten shells, so she has no teeth at her castle. Relatives of the genus Gryphaea from the family of Gryphaeidae are still widespread in the oceans.

Way of life

At specific localities Gryphaea - fossils are found in large quantities. 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 seabed, while the flat " lid " and opened the shell allowed the filtration of food. Therefore, the left tray is often referred to as " lower", the right as "upper" fossil collectors.

Evolution

The Gryphaea species from the layers of Lower Jurassic show a steady increase in size until the Middle Jurassic. This size increase is not due to a greater life expectancy and thus a higher age of later forms and types, but to larger growth rates. With the accelerated growth going features of heterochrony ( Pädomorphose ) associated.

Types (selection)

• Gryphaea arcuata, 6 cm, is found frequently in Germany and France, index fossil in the Sinemurian
• Gryphaea dilobotes, up to 14 cm, Western Europe, index fossil for the Callovian
• Gryphaea gigantea, 10 - 12 cm, is found in Western Europe in calcareous - marly facies, index fossil for the Pliensbachian