Unbranched, circular.

Category of architectural design: 2.63. Circular holes and pit-shaped borings.

Diagnosis: Flat, considerably large depressions of irregular oval or very elongated form, occuring on the surface of a firm limestone substrate. The outline is undulated, sometimes lobate, even with pointed prejections. The bottom is rounded, more or less smooth, in some individuals with flat protrusions or depressions. The walls are usually steep, perpenticular or slightly overhanging; borings often occur in large groups. The usual dimension at the surface of sibstrate is c. 50 mm, depth 10-15 mm.

Diagnosis. Grooves relatively deep, with sinuous pathway, with a width fairly uniform along its trajectory. Often they show points where the path is bifurcated reaching, in these cases, a width which can be the double of the normal diameter. Inside there are a number of lines or marks, more or less pronounced, with a concavity oriented in the animal's direction of movement.

Remarks. The characteristics of Ericichnus igen. nov. are somewhat similar to those of the ichnotaxon Planavolites Mikuláš 1992 described from the Lower Cretaceous at the Štramberk quarry in Moravia (Czech Republic). However, Ericichnus igen. nov. and Planavolites differ substantially in their general structure and dimensions between 150 to 300 cm and 1 to 9.5 cm in lenght, respectivelly. Ericichnus igen. nov. is a system of grooves having concave lines oriented in the animal's direction of movement and presenting a bifurcation model very well defined. By contrast, Planavolites don't exhibits never these characteristics (Mikuláš, 1992, pag. 307, Fig. 6). On the other hand, one of the most important distinctions between Ericichnus igen. nov. and Planavolites is the lack of hemispherical depressions associated with Circolites kotoucensis randomly distributed on the lateral margins of the grooves in the latter, for which there is no doubt that echinoids are the producers of Ericichnus igen. nov.