Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale 2351, Australia.
Division of Paleontology, American Museum of Natural History, New York, NY 10027, USA.
Proc Biol Sci. 2023 Jul 12;290(2002):20230638. doi: 10.1098/rspb.2023.0638. Epub 2023 Jul 5.
The stem-group euarthropod is one of the largest Cambrian animals and is often considered the quintessential apex predator of its time. This radiodont is commonly interpreted as a demersal hunter, responsible for inflicting injuries seen in benthic trilobites. However, controversy surrounds the ability of to use its spinose frontal appendages to masticate or even manipulate biomineralized prey. Here, we apply a new integrative computational approach, combining three-dimensional digital modelling, kinematics, finite-element analysis (FEA) and computational fluid dynamics (CFD) to rigorously analyse an feeding appendage and test its morphofunctional limits. These models corroborate a raptorial function, but expose inconsistencies with a capacity for durophagy. In particular, FEA results show that certain parts of the appendage would have experienced high degrees of plastic deformation, especially at the endites, the points of impact with prey. The CFD results demonstrate that outstretched appendages produced low drag and hence represented the optimal orientation for speed, permitting acceleration bursts to capture prey. These data, when combined with evidence regarding the functional morphology of its oral cone, eyes, body flaps and tail fan, suggest that was an agile nektonic predator that fed on soft-bodied animals swimming in a well-lit water column above the benthos. The lifestyle of and that of other radiodonts, including plausible durophages, suggests that niche partitioning across this clade influenced the dynamics of Cambrian food webs, impacting on a diverse array of organisms at different sizes, tiers and trophic levels.
干群节肢动物是最大的寒武纪动物之一，通常被认为是其时代的典型顶级掠食者。这种放射虫通常被解释为底栖猎人，负责造成底栖三叶虫身上的伤害。然而，关于能否使用其多刺的额前附肢进行咀嚼，甚至操纵生物矿化的猎物，存在争议。在这里，我们应用了一种新的综合计算方法，结合三维数字建模、运动学、有限元分析（FEA）和计算流体动力学（CFD），严格分析了一种干群节肢动物的进食附肢，并测试了其形态功能极限。这些模型证实了一种捕食功能，但暴露了其无法进行硬食的不一致性。特别是，FEA 结果表明，该附肢的某些部分会经历高度的塑性变形，尤其是在端节上，这是与猎物碰撞的地方。CFD 结果表明，伸展的附肢产生的阻力很小，因此是速度的最佳方向，可以允许爆发式加速来捕获猎物。这些数据，结合其口腔锥体、眼睛、体瓣和尾扇的功能形态学证据，表明是一种敏捷的游泳掠食者，以在透光水层中游泳的软躯体动物为食，该水层位于海底之上。干群节肢动物和其他放射虫动物的生活方式，包括可能的硬食者，表明这个分支的生态位分化影响了寒武纪食物网的动态，对不同大小、层次和营养级别的各种生物产生了影响。
