Diagnosis: Surface traces of circular or subcircular to oval-subpolygonal shape. In the simplest case, the boundary is revealed merely by a color difference in the substrate or, more often, by the presence of a shallow, ring-shaped furrow following a curved, rectilinear or festooned pathway. Within this outer furrow, as a rule, additional structures occur consisting of very faint, circular, oval, or subpolygonal concentric striations (Santos et al.,2005).

Unbranched, circular, etching traces.

Category of architectural design: 2.76. Single circular to tear-shaped attachment bioerosion traces.