The Acritarcha Their classification, morphology, ultrastructure and palaeoecological/palaeogeographical distribution Die Acritarcha Ihre Klassifikation, Morphologie, Ultrastruktur und palaeooekologische/palaeogeographische Verbreitung
Montenari, M.; Leppig, U.
Paläontologische Zeitschrift 77(1): 173-194
2003
ISSN/ISBN: 0031-0220
Accession: 038720857
The acritarchs are considered to form the oldest marine organisms with an eukaryotic cell organization. They are of great biostratigraphic, palaeoecological and palaeobiogeographic importance for the Precambrian and Early Palaeozoic. The present study provides a survey of their possible biological affinities. The main morphological characteristics of the acritarchs and their palaeogeographic and palaeoecological distribution are described and evaluated. Regarding the genesis of eukaryotes, the serial endosymbiosis theory (SET), the archaezoa theory, the fusion hypothesis and the hydrogen hypothesis are briefly described, compared and discussed. Significant differences of the evolutionary acceleration of the proterozoic acritarchs (negative acceleration of vesicle diameters and simultaneous positive acceleration of diversity) are described and interpreted in the light of the SET as an evidence for major reorganizations of the cell compartments.