Figure 2.

Sinocyclocyclicus guizhouensis, tabulate fossils interpreted as possible stem cnidarians. (A) Twenty clustered tubes, seen in oblique section. (B) Detail of slightly curved cross-walls. (C) Tube showing expansion at top. (E) The same specimen at higher magnification, illustrating the thickening and curvature of cross-walls where they meet tube walls (arrow). (D and J) Tube with large chamber at upper end; cross-walls are incomplete and curve downward to make side walls of the chamber—cross-walls beneath the chamber are complete. (F) Tube with phosphatic rim along inner surface of tube walls and both complete and incomplete cross walls, preserved as boundaries between the phosphatic infillings of adjacent chambers. (G) Detail of complete and incomplete cross-walls (arrow in F). (H) SEM of tube with a bulbous structure at the end (arrow), as well as a laminated phosphatic rim on the tube wall. (I) Folded tube, demonstrating original flexibility of wall. (The scale bar in A represents 100 μm for A and F; 25 μm for B, D, and E; 60 μm for C; 20 μm for G and J; 200 μm for H; and 150 μm for I.)