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
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
exceptionally well preserved, where the ovaries have been found
preserved, however it is very rare that soft bodied parts are preserved.
Picture 1, displaying fossilized ostracods.
One half of the carapace is visible.
Permission granted. Copyright of Karen Osborn and UC
Museum of Paleontology