Foraminifera

\n\n\n\n\n\n\n\nAllogromiida
\nCarterinida
\nFusulinida - extinct
\nGlobigerinida
\nInvolutinida
\nLagenida
\nMiliolida
\nRobertinida
\nRotaliida
\nSilicolocunida
\nSpirillinida
\nTextulariida\n The Foraminifera are a large group of amoeboid protists with reticulating pseudopods, fine strands that branch and merge to form a dynamic net. They produce more or less elaborate shells or tests, which are generally calcareous in composition and multi-chambered, varying in form from simple chains of compartments to spirals like snail-shells. Foraminiferans are marine, and are very common as benthos, although a few planktonic. They tend to be relatively large, a few reaching over 10 cm in diameter. Several thousand species are known, some living and some as fossils, which make up an important part of many marine sediments and are known as far back as the Cambrian period. The form of the shell is the primary means by which foraminferans are identified and classified. A few other amoeboids produce reticulose pseudopods but lack elaborate tests, and these have been considered possible relatives of the foraminiferans, grouped together as the Granuloreticulosea. However, their affinities appear to lie elsewhere, with the exception of Reticulomyxa, shown by genetic studies to be a foraminiferan that has lost its shell. Other groups that may be related include some Radiolaria and Cercozoa.
\nSEM micrographs of four benthic foraminiferans
(ventral view). Clockwise from top left: Ammonia beccarii,
Elphidium excavatum clavatum, Buccella frigida,
and Eggerella advena.