The last Mesozoic brachiopods

A remarkable discovery of the last Mesozoic brachiopods, dating to the topmost Maastrichtian chalk just below the Cretaceous–Paleogene (K–Pg) boundary clay at Stevns Klint, Denmark, sheds light on the climax of a specialized fauna that thrived in the Chalk Sea for 34 million years. This rich brachiopod assemblage, comprising 28 micromorphic species and 1967 individuals, represents the highest richness recorded from any Danish section at or near the K–Pg boundary, surpassing even the most benthos-rich parts of the Upper Cretaceous Chalk Group. The sample, derived from a 25 kg bulk chalk residue, showcases an extraordinary diversity and abundance, reflecting the full range of morphological adaptations to life on fine-grained seafloor. This finding underscores the unique macro-habitat of the Chalk Sea and provides critical insights into the evolutionary trajectory of its brachiopod fauna in the lead-up to the cataclysmic boundary event.

Surlyk, F., Jakobsen, S. L., & Hofstedt, M. (2026). The last Mesozoic brachiopods. Bulletin of the Geological Society of Denmark, 75, 223–234. https://doi.org/10.37570/bgsd-2026-75-12