Diagnosis: Excision of gastropod shell material, beginning at outer lip of aperture and extending backwards at least 5 into whorl with an aspect ratio of at least 0.3. Aspect ratio is defined as the depth of damage perpendicular to growth margin divided by height of damage parallel to growth margin. The shape of the trace ranges from slivers of shell removed from the aperture, subparallel to growth margin and potentially cross-cutting ornament; to larger portions of material removed, resulting in arcuate (V-shaped), W-shaped, or semicircular geometries. Extent of breakage parallel to growth margin is limited only by height of aperture. Extent of breakage perpendicular to growth margin is limited only by extent of shell’s whorls. Breakage profile can be jagged or clean. Breakage surface (when fresh and unrepaired) is sharp. In cases of repaired damage, the breakage can be marked by a disruption in shell surface topography. Disruption varies in depth depending on shell thickness, due to new shell growth commencing from interior surface of shell. With repaired damage, shell surface features, such as ornament or color patterns, can exhibit a slight to prominent mismatch between original shell and new growth.

Category of architectural design: 2.67. Fracture-shaped bioerosion traces.

Emended Diagnosis: Smoothly arcuate to linear excision or incision traces on shelled organisms originating from durophagous predation, especially cutting and peeling attacks. Traces propagate posteriorly from the anterior growth margin (i.e. commissure or aperture) at the time of attack. Repair scars are usually found associated with these traces.