Classification of Fossil Microplankton

Abstract

IT is becoming increasingly desirable that a definite decision be made as to whether the fossil organicshelled microplankton (dinoflagellates, hystrichospheres, and genera of presumed microplankton incertae sedis) should be classed, for nomenclatural purposes, in the animal or in the plant kingdom. The dinoflagellates, a group of unicellular organisms some of which contain chlorophyll, are clearly algae, while others contain no chlorophyll and are vagile and predatory, and are at present alternatively regarded as the class Dinoflagellata or class Dinophyeeae. The hystrichospheres, typically marine in occurrence and defined by their morphology, are regarded as an order incertae sedis, the order Hystrichosphaeridia, and have been treated by most authors as animals: the majority are now known to be dinoflagellate cysts, while others, less capable of definite attribution, may be zygospores of desmids, eggs of copepods or other planktonic organisms, or even plant spores.