and their relatives, including foraminifera and radiolaria,
belong to the subphylum Sarcodina. Foraminifera and
fossilize, which make them an important part of many
micropaleontological samples. Both foraminifera and
radiolaria have fossil records that date back to
are amoeba-like protists that build shells called
tests. The shell
is referred to as a test because some of the protoplasm
organism covers the outside of the test.
have chambers that are added as the cell grows. Shells
or tests can be made of sand and bits of discarded
that adhere to an exuded sticky
substance, a hard keratin-like material, or calcite
can be planktonic or benthic. Many
tropical beaches are composed of sands made primarily
from the skeletons of benthic foraminifera. Much
of the ocean floor that is less than 4.000 m deep is
by calcareous ooze composed of microfossil
shells made of calcite. Forams that secrete tests of
calcite are not typically found below this depth because
dissolve. The calcite compensation depth (CCD) is the
depth at which
5,000 meters. Below this depth forms that construct
their tests from cemented grains of sand or other foreign
are more common.
move, feed, and excrete waste using pseudopodia or
cell extensions that project through pores in their
Foraminifera are a key part of the marine food chain.
They ingest smaller microorganisms and detritus; in
turn, formams serve as food for larger organisms. Some
forams, like the extinct nummulitids and fusulinids,
possess symbiotic algae (photosymbionts).
calcium carbonate from nannoplankton
and foram shells
over long periods of time formed many
Late Cretaceous deposits of white, fine-grained limestone known
as chalk (Curtis, 1980, p. 370). The
White Cliffs of Dover and other Late Cretaceous chalky deposits
around the world are made primarily from coccolithophores,
with forams taking
on a secondary role (Prothero, 2007, p. 175). Coccolithophores,
known as calcareous nannoplankton, are calcifying protists in
the phylum Haptophyta. Coccolithophores are one of the major
primary producers making up a significant portion of the phytoplankton.
In today's oceans coccolithophores are also responsible for half
of all calcium carbonate precipitation, thus they are central
to the global carbon cycle (De Vargas, Aubry, Probert, & Young,
2007, p 251).
the Cambrian to the present,
role in the marine biosphere as a key part
of the food chain.
Because their shells (tests) have evolved
over time it is possible to use them for correlating
In fact, more
paleontologists specialize in foraminifera than
any other fossil group (Prothero, 1998, p. 190). As
fossils, forams have multiple uses:
forams are the standard for correlating Mesozoic
and Cenozoic marine strata
are the main index fossil for the late Paleozoic
sensitivity to temperature, chemistry and depth allow
them to be used as clues to past climates and marine
depositional environments. This last use is critical
to the search for oil deposits.
are amoeba-like protists that build an internal skeleton
out of opaline silica. The delicate geometric shapes
of these tests may remind one of snowflakes or even Christmas
ornaments. Radiolarians are typically half the size of
forms and are strictly planktonic, none are benthic.
Rigid and flexible pseudopodia protrude from the silica
and are used to capture and ingest coccolithophorids,
diatoms, bacteria, and other plankton. Like forams, some
posses symbiotic algae. Radiolaria, like forams, are
an important food source for many larger organisms.
tropical ocean floors below the CCD calcareous foraminifera
and nannofossils are dissolved away, leaving a siliceous
ooze formed from the silica shells of microfossils. These
siliceous sediments are called radiolarites. When
radiolarites turn to rock they form chert.
fossils provide clues for determining past climates
as well as
depth, and geography of ancient oceans. Like foraminifera,
radiolarians evolved rapidly, accumulating in thick
sedimentary deposits. This makes their biostratigraphy
very useful. This is especially true for calcium carbonate
poor oceanic sediments, such as those formed in the
Arctic and Antarctic regions (Prothero, 2004, pp. 201-206).
Science Olympiad Fossil Event
2016 Science Olympiad Fossil list includes two types
of forams, Nummulites (Latin:
nummulus for "little coin" in reference to
their shape) and Fusulinids. The Egyptian Pyramids are
of Eocene aged nummulitic limestone. Forams are in the
Kingdom Protista, Phylum Sarcomastigophora, and
(Olney, 2008, Foraminifera page). To learn more about Foraminifera read Foram Facts. Fusulinids are similar to wheat grains in shape and size. The fusulinids in the limestone below are most likely in the genus Triticites from the Latin for wheat tritic and the English for rock or fossil ite (Borror, 1988, pp 50 and 105).
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D.R. (2004). Bringing Fossils to Life: An Introduction
to Paleobiology [2nd edition]. New York: McGraw-Hill.
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