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 in...近期观测结果显示，壳体破碎（shell fragmentation）可作为评估海洋群落内粉碎性捕食（crushing predation）的有效工具。然而，区分硬食性捕食者（durophagous predators）所致壳体破损与物理因素引发的壳体破损的判别标准，目前仍未得到明确建立。本文借助翻滚实验与水族箱实验的数据，证实物理过程与生物过程会催生不同的壳体损伤模式——具体而言，棱角状壳体碎片可作为硬食性捕食的优良指示指标。我们以该类棱角状壳体碎片作为捕食替代指标（predation proxy），对57处欧洲古生代（Paleozoic）产地的数据展开分析，其时代跨度覆盖奥陶纪（Ordovician）至密西西比纪（Mississippian）。研究结果表明，密西西比纪地层中棱角状壳体碎片（包括孤立壳瓣或反刍粪化石（regurgitalites）内的壳体碎片）的占比显著升高。该丰度升高的时间节点，与粉碎性捕食者多样性的提升，以及无脊椎动物在壳体结构与生活方式上出现的显著反捕食特征变化均高度一致。