PALEO LABORATORY # 3, PAGE 1
PALEO LAB # III - MESOZOIC AND CENOZOIC MICROPALEONTOLOGY
A. Kingdom Protoctista/Protista
During this lab, we will study various types of marine algae and the groups of autotrophic
protists, foraminiferans and radiolarians that were important during Mesozoic and Cenozoic
As we have seen in Laboratory # II, a number of photosynthetic divisions of Protoctista
have substantial fossil records.
These include the divisions Phaeophyta (brown algae),
Rhodophyta (red algae), Bacillariophyta (diatoms), Haptophyta (calcareous nannoplankton or
coccoliths; diatoms and calcareous nannoplankton are often placed within the Chrysophyta),
Pyrrhophyta/Dinoflagellata (dinoflagellates) and Chlorophyta (grass-green algae).
1. Division Pyrrhophyta/Dinoflagellata
You have probably read of the phenomenon termed "red tide", where ocean water turns a
reddish color and marine animals die by the millions.
Red tide is due to the rapid multiplication
and super-abundance of dinoflagellates, which produce a toxin called "paralytic shellfish
However, other dinoflagellates are not as destructive to the marine environment.
types are largely responsible for luminescence in the seas, where the surface waters of the ocean
seem to "twinkle" at night from the light produced by these organisms.
Dinoflagellates are very numerous organisms; they may be found in concentrations of up to
six million individuals per liter of sea water.
Most dinoflagellates are marine planktonic.
However, some species live in fresh water, others may be marine benthonic and other types are
symbiotic or parasitic.
During certain times in their life history, the "shells" of dinoflagellates are differentiated into
The outer layer, or theca, is composed of a cellulose-like substance which decays
when the algae dies.
However, the inner layer (test or cyst) is made of a tough, resistant organic
substance which is easily fossilized.
Because of the abundance, preservability and minute size of
dinoflagellates they are very important index fossils for determining the age and paleoecology of
ancient sedimentary environments.
Dinoflagellate tests with long spines (termed processes) are
often referred to as Hystricospheres (Jurassic-Recent).
Hystricospheres are planktonic and are
usually found in open marine environments.
Other dinoflagellates in which the spines are short
or absent (proximate tests) are most often found in near-shore environments.
distribution of the hystricosphere and proximate types is gradational and determination of the
paleoecology of fossil dinoflagellates is somewhat complex.
A third type of cyst, termed cavate,
forms a distinct central body (endocyst) beneath the tabulation.
It is difficult to relate fossil cysts to the "motile" phases of living dinoflagellates.