Diagnosis: Circular or subcircular in shape, exposed by a discolored zone that differs in preservation state from the neighboring surfaces or a very shallow ring-shaped furrow with a curved pathway. The inside is smooth or exhibits concentric circular etched rings (Santos et al., 2005).

Description: They are single or grouped subcircular traces in the form of a flat disk with diameter 0.7–5.6 mm, slightly raised above the surface of the host shell and with a sharply developed margin. The disk is limited by a shallow furrow on the outer side; in weakly preserved specimens the trace margin is limited only by a ring of light color. On the surface of two specimens, the smaller concentric ringis also developed at a 2/3 distance of the radius from the tracecenter.The traces touch together on several places, but without visible overlay. Increment lines of the host shell are visible on the disk surface with the same intensity as in surrounding unaltered shell surface.