DOI: 10.7291/d1696v
title: The role of bioturbation-driven substrate disturbance in the Mesozoic brachiopod decline

description: Brachiopods dominated the seafloor as a primary member of the Paleozoic
 fauna. Despite the devastating effects of the end-Permian extinction, the
 group recovered during the early Mesozoic only to gradually decline from
 the Jurassic to today. This decline likely had multiple causes, including
 increased predation and bioturbation-driven substrate disruption, but the
 role of changing substrate is not well understood. Given the importance of
 substrate for extant brachiopod habitat, we documented Mesozoic-Cenozoic
 lithological preferences and morphological changes to assess how
 decreasing firm-substrate habitat may have contributed to the brachiopod
 decline. Compared to bivalves, Mesozoic brachiopods occurred more
 frequently and were disproportionately abundant in carbonate lithologies.
 Although patterns in glauconitic or ferruginous sediments are equivocal,
 brachiopods became more abundant in coarser-grained carbonates and less
 abundant in fine-grained siliciclastics. During the Jurassic, brachiopod
 species rarely had abraded beaks but tended to be more convex with a high
 beak, potentially consistent with a non-analogue lifestyle resting on the
 seafloor. However, those highly-convex morphotypes largely disappeared by
 the Cenozoic, when more terebratulides had abraded beaks, suggesting
 closer attachment to hard substrates. Rhynchonellides disproportionately
 declined to become a minor component of Cenozoic faunas, perhaps because
 of less pronounced morphological shifts. Trends in lithological
 preferences and morphology are consistent with bioturbation-driven
 substrate disruption, with brachiopods initially using firmer carbonate
 sediments as refugia before adapting to live primarily attached to hard
 surfaces. This progressive habitat restriction likely played a role in the
 final brachiopod decline, as bioturbating ecosystem engineers transformed
 benthic habitats in the Mesozoic and Cenozoic.
description: Contains measurements and descriptive categorization of shell
 morphology, especially related to the pedicle foramen and beak, for
 Jurassic-Recent terebratulide and rhynchonellide species. These
 include: Width of pedical foramen opening, as a
 proportion of shell length (foramen_width). Based on a single individual,
 either the holotype or a representative specimen.
 Height of umbo (linear distance), as a proportion of shell length
 (umbo_height). Based on a single individual, either the holotype or a
 representative specimen. Angle of umbo, measured
 relative to commissure in lateral view. An angle of 0 represents a
 straight umbo that is parallel to the commissure, while an angle of 90
 degrees represents an erect/incurved umbo that is perpendicular to the
 commissure. Based on a single individual, either the holotype or a
 representative specimen. Shell width/length (WL) and
 height/length (HL). Based on the mean of all measurements in the
 Paleobiology Database. The file also notes whether the
 pedicle foramen is labiate, whether the beak is abraded (beak_weathering),
 and whether there is shell thickening, usually in the dorsal valve. Traits
 were assigned based on published descriptions and illustrations, and
 represent the typical condition for each species. In these columns, blank
 entries typically mean that the feature is not present, but some of the
 features vary among specimens or during ontogeny.