FOSSIL PROTOBIONTA AND THEIR OCCURRENCE 



A. Papp 



Department of Paleontology, University of Vienna, Vienna, Austria 



The body of paleontological research consists essentially of knowledge of 

 organisms having a preservable skeleton. Therefore, one cannot expect that 

 the oldest organisms will have been preserved. Amino acids, but not the 

 organisms themselves, have been found in lower Precambrian limestone. The 

 earliest phase — origin of the basic building blocks, their development into 

 primitive organisms, as well as the primary evolutionary forms — is beyond the 

 scope of present paleontological basic research. 



By the Cambrian (600 million years ago) many highly diversified skeleton- 

 forming organisms had developed. Therefore these organisms are within the 

 focus of paleontological research. At that time life had already attained a 

 considerable level of evolution, with almost all the invertebrate families present. 

 In spite of this fact, our knowledge of fossil protobionta is still incomplete; it is 

 quite possible that a whole array of different organisms is still unknown. How- 

 ever, the following groups may be classified: (1) bacteria; (2) protobionta with 

 a preservable outer skeleton of organic material; (3) protobionta with an outer 

 skeleton of inorganic material; and (4) sporomorpha and spores. 



(1) The presence of fossil bacteria has been revealed by different techniques. 

 Since 1960 H. Dombrowsky's observations regarding bacteria from paleozoic 

 salt deposits have shown, however, that paleobacteriology is still in its infancy. 

 The role of anaerobic or sulfate-reducing bacteria in the development of Ufe 

 lies outside the field of paleontology. 



(2) In the group of protobionta with preservable outer skeleton those com- 

 posed of organic material are believed to be the older species. In this group 

 only the already relatively complicated structures are known, among them such 

 Dinoflagellate forms as Chitinozoa and Hystrichosphaeridae. Fossil Hystri- 

 chosphaeridae with shells of material resembling cutin, which developed in the 

 Cambrian, cannot be readily distinguished from later forms. In fact, their 

 close resemblance to spores of fungi (Zygospores) is noteworthy. Skeletons of 

 fossil protobionta show remarkable resistance under suitable conditions of 

 fossilization. 



(3) Microorganisms of simple structure, such as Archaemonadidae, Sili- 

 coflagellatae, Diatoms, and Radiolaria, deposit silica in their shells. Fora- 

 minifers built shells by cementing stone particles with calcite, or occasionally 

 of calcite alone. In rare instances they employed chitin-like substances. In 

 contrast, Dinoflagellata seusu lata, undoubtedly represent a later phase in 

 evolution and offer a vast amount of material for research. Coccolitho- 

 phoridean skeletons show small calcite particles which may form rock strata 

 under favorable conditions of fossilization. 



(4) The terms sporomorpha and spores imply a state of reproduction con- 

 siderably different from the fully developed organism. Their resistant outer 

 layer (exine) composed of sporopoUinin ensures preservation under favorable 

 conditions. Sporomorpha and spores result from reduction division, which 



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