Page 217 - Introduction to Paleobiology and The Fossil Record

Chapter 9

Protists

Key points

• Micropaleontology is a multidisciplinary science, focused on the study of microorgan-
isms or the microscopic parts of larger organisms.
• Prokaryotes, unicellular microbes lacking nuclei and organelles, include the carbonate-
producing cyanobacteria, the oldest known organisms; their radiation during the mid-
Precambrian promoted an oxygen-rich atmosphere.
• Protists, unicellular organisms with nuclei, include a large variety of organisms with
external protective coverings (tests and cysts) assigned to the kingdoms Protozoa and
Chromista.
• Fossilized protists can also be split into organisms with organic (acritarchs, dinofl agel-
lates, chitinozoans), calcareous (coccolithophores, foraminiferans) or siliceous (diatoms,
radiolarians) skeletons.
• Foraminifera, single-celled animal-like protozoans, contain both benthic and planktonic
forms with chitinous, agglutinated, but most commonly calcareous (hyaline and porcel-
laneous), tests occurring throughout the Phanerozoic.
• Radiolarians, animal-like protozoans with siliceous tests, and diatoms, plant-like pro-
tozoans with silicic skeletons, are both important rock formers.

• Acritarchs, dinoflagellates and chitinozoans are palynomorphs, most commonly pre-
served as cysts, with important biostratigraphic applications. The first two are assigned

to the protozoans, the third is currently difficult to classify.

• Coccolithophores and diatoms are assigned to the chromistans.

It has long been an axiom of mine that the little things are infi nitely the more
important.

Arthur Conan Doyle (1891) A Case of Identity