Proterozoic and living cyanobacteria

The satisfactory systematic and functional interpretation of any fossil requires that its features be comparable to those of living organisms. A conundrum facing paleontologists who study Proterozoic microfossils is that many of the cyanobacteria-like remains that are so abundant in microbial mat assemblages have multiple morphological analogues in the modern biota -organisms that range from oxygenic photoautotrophs (the cyanobacteria) to anaerobic heterotrophs. Interpretation, therefore, requires that careful attention be paid to paleoenvironmental, behavioral, and taphonomic considerations, as well as morphology. Analyses of Proterozoic microfossil populations, including species of Eoentophysalis, Polybessurus, Eohyella, and others, demonstrate how paleobiological interpretation is maximized when careful observations on ancient populations are combined with complementary studies of modern morphological, developmental, and behavioral counterparts living in comparable physical environments.