THE EVIDENCE OF REPRODUCTIVE MECHANISMS IN FOSSIL DASYCLADS (ALGAE: CHLOROPHYTA)

Dasyclads (members of Order Dasycladales: Algae, Chlorophyta) are reviewed for evidence of reproductive structures in the fossil state, and then compared with what is known of the reproductive processes in living examples. The effects of poor preservation in most of the fossils are shown to result in many uncertainties, and the resulting degree of interpretation required is emphasized. Selected genera of fossil dasyclads considered relevant to this problem are briefly analysed and discussed: Archaeobatophora (Ordovician), Kulikia (Carboniferous), Imperiella (Permian), Stichoporella (Jurassic) and Cympolia (Cretaceous to Recent). The pioneer views of J. Pia on dasyclad reproduction through geological time are seen to need much modification in the light of later work. The fundamental dasyclad nucleus-fragmentation-reproduction mechanism is believed to have operated within the great morphological variety of known dasyclads, giving rise to modification in genera where basic evolution was structural. In this way the variety of dasyclads can be seen to be the result of varied morphological evolution, often modified by the consistently simple basic reproductive mechanism.