The role of bioturbation-driven substrate disturbance in the Mesozoic brachiopod decline

Abstract

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 lithologic preferences and morphological changes to assess how decreasing firm-substrate habitat may have contributed to the brachiopod decline. Compared with 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 lithologic 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.

Bayesian analyses indicate bivalves did not drive the downfall of brachiopods following the Permian-Triassic mass extinction

“…Infaunal bivalves, in contrast, have more diverse feeding behaviours and occupy different niches from brachiopods. Although the activities of infaunal bivalves may disrupt substrates and thus affect occupation by brachiopods 66 , 67 , it is a quite different mechanism from direct competition. For this reason, the MBD analysis was also conducted for the three ecological groups, epifaunal brachiopods, epifaunal and infaunal bivalves.…”

“…31 ). These factors have been widely tested to explain the diversification dynamics of marine organisms including brachiopods and bivalves 20 , 65 , 67 , 113 – 117 . The trajectory of seawater temperature came from Scotese et al 75 ; their ‘global average temperature’ estimated from oxygen isotopes (δ 18 O) was adopted.…”

“…The vast majority of the post-Permian brachiopods were pedicle-attached. Mesozoic brachiopods became more and more frequent in carbonate lithologies which are on average firmer than siliciclastics, and the loss of habitats because of strengthened bioturbation possibly drove the Mesozoic–Cenozoic decline of brachiopods 67 . To approximate habitat availability, we calculated the proportion of occurrences (of all brachiopods and bivalves) reported from carbonate lithologies at the substage level.…”

The Phanerozoic aftermath of the Cambrian information revolution: sensory and cognitive complexity in marine faunas

“…The rise of ganglionated taxa heavily reflects the radiation of bivalves and bryozoans, which were absent or rare in the Cambrian faunas, though we also consider some potential underrepresentation of ganglionated Cambrian invertebrates among the excluded “problematica” based on uncertain coding (well-cephalized groups like arthropods and decentralized ones such as echinoderms were perhaps more clearly assigned to their nervous system level). A Phanerozoic increase in ganglionated animals relative to those with simpler nervous systems might also reflect an increase in motile benthos able to respond to disturbance (Bush et al 2007; Manojlovic and Clapham 2021), a change expected to increase at least some information-processing abilities.…”

How long does a brachiopod shell last on a seafloor? Modern mid‐bathyal environments as taphonomic analogues of continental shelves prior to the Mesozoic Marine Revolution

“…2012; Suchéras‐Marx et al . 2019; Tackett & Tintori 2019; Manojlovic & Clapham 2021; Buatois et al . 2022; Cueille et al .…”