Orthogonum lineare Glaub, 1994

Description: O. lineare consists of tubes of relatively constant diameter of 7 to 12 (9.96 ± 1.7, n = 59) μm wide (Fig. 12a). This was previously described by GLAUB (1994) with diameter 7–16 µm, pl. 7, fig. 1–4.). O. lineare has a smooth surface and round cross-section (Fig. 12c). Ramifications occur at variable intervals, at nearly right angles (Fig.12b) conforming to the ichnogenus diagnosis. Tunnels have smooth surfaces (Fig. 12b) and rounded, sometimes slightly inflated tips (Fig. 12c). The lack of anastomosis and the avoidance of pre-existing tunnels is consistent, even when there is a high density of filaments. Filaments arch over each other or are deflected (Fig. 12c). Tubules often run parallel to each other (GLAUB, 1994, fig. 37; pl. 7, figs. 2 and 4), avoiding the edge of the substrate as well as each other. In light-microscopic preparations, the tunnels were found to contain gray-coloured content. The SEM of fractured tunnels shows some of our samples to contain spore-like bodies.