A cluster of the brachiopod Magas chitoniformis (von Schlotheim, 1813) represents settling of a single spatfall on a soft-bodied substrate, probably a sponge: instantaneous burial by a chalk ooze debris flow (Maastrichtian, Denmark).

A remarkable discovery at Stevns Klint, Denmark, reveals a monospecific cluster of the brachiopod Magas chitoniformis preserved in uppermost Maastrichtian chalk. The 53 well-preserved specimens, exhibiting a unimodal size-frequency distribution, indicate they represent a single successful spatfall likely attached to a soft-bodied sponge. The absence of transport or winnowing suggests instantaneous burial by a chalk ooze debris flow, potentially triggered by a major earthquake in the tectonically active Sorgenfrei-Tornquist Zone. This finding provides exceptional evidence of brachiopod attachment to a soft-bodied organism, offering insights into paleoecological dynamics and sedimentary processes during the Late Cretaceous.

Surlyk, F. (2025). A cluster of the brachiopod Magas chitoniformis (von Schlotheim, 1813) represents settling of a single spatfall on a soft-bodied substrate, probably a sponge: instantaneous burial by a chalk ooze debris flow (Maastrichtian, Denmark). Bulletin of the Geological Society of Denmark, 74, 15–24. https://doi.org/10.37570/bgsd-2025-74-02