Phosphatized Epiphyton from the terminal Neoproterozoic and its significance

The fossil record of calcified cyanobacteria in the Precambrian is scarce, especially for fossils with dichotomous filaments. Epiphyton, which have complex branching structures like cyanobacteria and are usually regarded as calcimicrobe with uncertain affinity, and are widely considered to appear at the beginning of the Cambrian. Exceptional phosphatized three-dimensional Epiphyton are reported from the Gaojiashan Member, Dengying Formation of the terminal Neoproterozoic, Lijiagou section, southern Shaanxi Province of China. Based on data from scanning electron microscopy and X-ray tomographic microscopy, two preservational modes of Epiphyton, namely tubular and solid branches, and their corresponding phosphatic processes are proposed. Branching forms of the thallus, sizes, and outer surface ornamentations of the filaments are characteristic of Phanerozoic Epiphyton, and has allowed us to give a possible interpretation of this genus, and to recognize its similarity to cyanobacteria. The finding enhances our understanding of the diversity of cyanobacteria in the terminal Neoproterozoic, give us an opportunity to reassess the theories involving the coevolution of calcification of microbes and metazoans.