Data from: Trends in shell fragmentation as evidence of mid- Paleozoic changes in marine predation

Recent observations indicate that shell fragmentation can be a useful tool in assessing crushing predation in marine communities. However, criteria for recognizing shell breakage caused by durophagous predators versus physical factors are still not well established. Here, we provide data from tumbling and aquarium experiments to argue that physical and biotic processes lead to different patterns of shell damage, specifically that angular shell fragments are good indicators of durophagous predation. Using such angular shell fragments as a predation proxy, we analyze data from 57 European Paleozoic localities spanning the Ordovician through the Mississippian. Our results reveal a significant increase in angular shell fragments (either occurring as isolated valves or present in regurgitalites) in the Mississippian. The timing of this increase is coincident with the increased diversity of crushing predators as well as marked anti- predatory changes in the architecture and mode of life of invertebrate prey observed after the end-Devonian Hangenberg extinction (359 Ma). More specifically, the observed trend in shell fragmentation constitutes strong and independent confirmation of a recently suggested end-Devonian changeover in the primary method of fish predation from shearing to crushing. These results also highlight the important effect of extinction events, not only on taxonomic diversity, but also on the nature of predator-prey interactions.

近期观测结果表明，壳体破碎（shell fragmentation）可作为评估海洋群落内压碎型捕食压力的有效工具。然而，区分由碎食性捕食者（durophagous predators）造成的壳体破损与物理因素诱导的壳体破损的判别标准，目前仍未得到明确确立。本研究借助翻滚实验与水族箱实验获取的数据，证实物理过程与生物过程会形成迥异的壳体破损模式——具体而言，棱角状壳体碎片可作为碎食性捕食的可靠代用指标。我们以该类棱角状壳体碎片作为捕食作用的替代指标，对覆盖奥陶纪至密西西比纪的57处欧洲古生代遗址开展数据分析。结果显示，密西西比纪地层中棱角状壳体碎片（包括孤立壳瓣或留存于食团粪化石（regurgitalites）中的碎片）占比显著提升。该增长节点与两大关键事件的时间高度吻合：一是碎食性捕食者多样性的显著增加；二是泥盆纪末哈登伯格灭绝事件（359 Ma）后，无脊椎动物猎物在躯体结构与生活模式上出现的显著反捕食适应性演化。更具体地说，本次观测到的壳体破碎趋势，为近期提出的"泥盆纪末鱼类捕食方式从剪切式转向压碎式"这一假说提供了强有力的独立佐证。本研究结果同时凸显了灭绝事件的重要影响：其不仅会改变类群的分类多样性，还会重塑捕食者与猎物间的相互作用本质。