University of Bristol logo and link Fossil Groups banner and link

Fossil Record

    Ostracods have a long and good fossil record, ranging from the Cambrian period until present. They are particularly dominate in the Ordovician sediments and provide one of the most complete and consistent fossil records of any animal. Their low magnesium calcite carapace is what is usually preserved in the fossil record either as single valves or with both valves together as a complete carapace.

Picture 1 below shows an example of a fossil ostracod.

    Geologists and palaeontologists view ostracods as important index fossils and use them to date sediments (biostratigraphy) as they have a wide geographic distribution. They can be found in limestone, shales and marine marls. Occasionally deposits of ostracods can be so extensive they form a type of limestone (referred to as coquinas), which can be used for building. Researches have found that by studying the condition of the carapace and the location they are found within that it is possible to determine water depth and salinity, sedimentation, temperature and other palaeoecological factors. Generally the more ornamented forms are the most useful in correlation.
    They have important applications in the oil and gas industry.
Some female ostracods have been found exceptionally well preserved, where the ovaries have been found preserved, however it is very rare that soft bodied parts are preserved.

Fossilised ostracod. One half of a carapce is visible.
Picture 1, displaying fossilized ostracods.
One half of the carapace is visible.
Permission granted. Copyright of Karen Osborn and UC Museum of Paleontology.