Pub. date: 2008 | Online Pub. Date: April 25, 2008 | DOI: 10.4135/9781412963893 | Print ISBN: 9781412958783 | Online ISBN: 9781412963893| Publisher:SAGE Publications, Inc.About this encyclopedia
FORAMINIFERA ARE MARINE eukaryotic unicellular organisms that construct a shell or test. They use chemicals from their surroundings to construct calcareous or siliceous crystals, or particulate grains to form an agglutinated test. They are heterotrophic protoctists with granular reticulopods (pseudopodial networks) exhibiting two-way streaming. Fora-minifers are Linnean classified by their chemistry, mineralogy, structure of the test walls, cytology, and DNA of protoplasm. Foraminifers can be either benthic or planktonic. Benthic foraminifers, in the shape of simple agglu-tinated tubes, lived in the Cambrian (500 million years ago). Planktonic foraminifers appear in the fossil record during the Jurassic (206 million years ago). Both variants provide excellent fossil records and are the most diverse group of shelled marine microorganisms on Earth. Most live in specific environments and cannot survive drastic environment changes. Most foraminifers evolve relatively quickly ...