Comparison of living and Precambrian cyanobacteria. Living examples (
A, C, E, and
G) are from mat-building stromatolitic communities of northern Mexico. (
A)
Lyngbya (Oscillatoriaceae), encompassed by a cylindrical mucilaginous sheath (arrow). (
B)
Palaeolyngbya, similarly ensheathed (arrows), FIGURE 2 (Continued) from the 950-Ma-old Lakhanda Formation of eastern Siberia. (
C)
Spirulina (Oscillatoriaceae). (
D)
Heliconema, a
Spirulina-like cyanobacterium from the
850-Ma-old Miroedikha Formation of eastern Siberia. (
E)
Gloeocapsa (Chroococcaceae), a four-celled colony having a thick distinct encompassing sheath (arrow). (
F)
Gloeodiniopsis, a similarly sheath-enclosed (arrow)
Gloeocapsa-like cyanobacterium, from the
1550-Ma-old Satka Formation of southern Bashkiria. (
G)
Entophysalis (Entophysalidaceae). (
H)
Eoentophysalis, an
Entophysalis-like colonial cyanobacterium from the
2-Ga-old Belcher Group of Northwest Territories, Canada (Golubic and Hofmann, 1976).