Vagorichnus anyao (Wu, 1985)

Description: Three-dimensional burrow system formed by curved, irregularly meandering or more rarely straight segments and ridge-like knobs. Commonly, burrow segments branch at acute (Y-shaped) or right (T-shaped) angles, defining highly irregular rectangular to polygonal networks of variable dimensions (Figs. 2, 9). Side branches are locally present (Fig. 9). The course of the burrows is typically discontinuous. Horizontal segments tend to disappear, adopting oblique or probably vertical orientations, only to re-emerge as a row of ridge-like knobs (Figs. 7,10). Burrows are characterized by the presence of annulations (Figs. 4, 7, 8, 9) or constrictions (Figs. 3, 9, 11). The annulations and constrictions are irregularly distributed throughout the burrow, mostly concentrated on some sectors of the course and absent in other parts. In this latter case, the burrow surface is smooth. Roughly annulated and constricted segments seem to be transitional with the ridge-like knobs (Fig. 11). Burrow linings have been locally detected. Burrows are flattened to subcylindrical. Diameter ranges from 2.3 to 4.7 mm (Fig. 12). Diameter is relatively constant within individual specimens; minor changes are related to variations in the depth of the burrow. Length of continuous burrows is up to 115 mm. In discontinuous burrows, short segments of 3-46 mm are separated by intervals up to 14 mm. Dimensions of networks are variable, the smallest being 6.8 cm2, the largest 192.4 cm2. Side branches are up to 3.30 mm wide and 23.3 mm lon.g