CHAPTER 1 Thal lophyta 1

This chapter includes all benthonic algae (planktonic algae are in Chapter 2), the family Prototaxitaceae, bacteria nd fungi. In some of these groups the fossil record is very inadequate, and the method of documentation has been varied accordingly. THE CALCAREOUS ALGAE Algae are the only fossil group which ave a widespread evelopment in the Precamb. The earliest fossil records, dating from at least 2700 m.y., are stromatolites possibly belonging to the Chlorophyceae and Cyanophyceae. Definite cellular microorganisms, including Gunflintia, Animikiea nd Archaeorestis identified as blue-green algae, have been found in the Gunffint Chert, M. Precamb, Canada, and are 1900 m.y. old (Barghoorn and Tyler 1965; Cloud 1965). Even at the earliest period there seems to have been considerable diversity in the group and since then continuous evolutionary progress has taken place. Divergence, convergence and parallelism of form and habit in the different classes of algae during their geological history is striking (Fritsch 1948). Thus the structural pattern of the Chlorophyceae, Cyanophyceae nd in most part the Rhodophyceae is remarkably parallel from unicellular motile and colonial, through filamentous to complex thaUoid forms