UC Santa Cruz

Brachiopods dominated the seafloor from the Ordovician to the Permian as one of the primary members of the Paleozoic fauna. Despite the devastating effects of the Permian-Triassic extinction, the group mounted a successful recovery during the Triassic and Jurassic, which was followed by their final decline. One proposed cause of this decline is the large increase in bioturbation associated with the Mesozoic Marine Revolution, leading to brachiopods shifting to harder substrates. This hypothesis was explored using occurrence and abundance data downloaded from the Paleobiology Database, with carbonate lithologies serving as a proxy for hard substrates and siliciclastics as a proxy for soft substrates. Brachiopods were more common on carbonate substrates in the Mesozoic which suggests a shift to harder substrates due to rapidly increasing bioturbation during the era. The resulting restriction to harder substrates is a contributor to the Mesozoic decline of brachiopods. Though increasing bioturbation has been previously proposed as a cause of brachiopod decline, this study provides additional quantitative support for this hypothesis.