Cutting-edge technology: burrows lined with sponge bioclasts from the Upper Cretaceous of Denmark

Many tracemakers use different materials to line their burrows. Koptichnus rasmussenae n. igen. n. isp. is lined with cuboid fragments of siliceous sponges, interpreted as evidence of harvesting and trimming material to reinforce the burrow wall. The act of trimming, as evidenced in the polyhedral faces, is considered to be behaviourally significant. The tracemaker was evidently a lobster-like crustacean.