Graptolites
Graptolietes are part of the phylum Hemichordata. Graptolites occur is sediments from the middle Cambrian to the beginning of the Carboniferous period. Many graptolites were planktonic and floated in the upper part of the ocean waters. There external skeleton was made of organic material (chitine) and not of chalk. Graptolites formed colonies by asexual reproduction.
When they died, the skeletons sunk to the bottom en were preserved in laminated clays under anoxic conditions. Because of the anaerobic (without oxygen) environment the organic material was preserved. Graptolites were flattened in the black shales, and look like jigsaws in many varieties.
Graptolites occur in great numbers in deep sea sediments from the Ordovician and Silurian periods. In these periods graptolites are used as guide fossils.
Example of the graptolite Monograptus from Bornholm, Denmark.
 Click here for information where to find these fossils.
 Go to the Photo page to view photographs of Graptolites. |
