Queuing behaviour has been documented in marine arthropods from Cambrian to modern oceans. It was previously hypothesized that this behaviour provided energy savings through hydrodynamic drafting, with trilobites in following positions hypothesized to produce less drag than those leading. In this study, we evaluate the hydrodynamics of queuing behaviour in the Devonian trilobite Trimerocephalus chopini using computational fluid dynamics. The results show that the drag forces of the trilobites following in the queue were substantially lower than those produced by the leader (˜65–79% lower at velocities of 0.5–2 cm s⁻¹). Drag reduction was positively correlated with the movement speed of the trilobites, but decreased with increasing distance from the leader, and there was essentially no drag reduction at all for the first following trilobite when the following distance was greater than about six times its body length. This agrees with fossil evidence preserving trilobites in queues in close proximity to each other. The results also show that drag reduction was still significant (˜86.8% at 2 cm s⁻¹) even for the longest queues preserved in the fossil record. Our findings support the hypothesis that the queuing behaviour of trilobites was an adaptation for reducing hydrodynamic drag. This drag reduction effect compensated for the energy cost of movement, which would have been particularly advantageous during migration.

中文翻译：

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计算流体动力学证实了与三叶虫排队行为相关的减阻

从寒武纪到现代海洋，海洋节肢动物的排队行为已被记录。之前假设这种行为通过流体动力牵引提供了能量节省，假设三叶虫在后面的位置产生的阻力比前面的小。在这项研究中，我们使用计算流体动力学评估了泥盆纪三叶虫Trimerocephaluschoppini排队行为的流体动力学。结果表明，在队列中跟随的三叶虫的拖曳力大大低于领先者产生的拖曳力（在 0.5-2 cm s ^{-1 的}速度下低约 65-79%）。减阻与三叶虫的移动速度呈正相关，但随着与前导距离的增加而下降，当跟随距离大于其体长的六倍左右时，第一个跟随的三叶虫基本上没有减阻。这与在彼此靠近的队列中保存三叶虫的化石证据一致。结果还表明，即使对于化石记录中保存的最长队列，减阻仍然显着（在 2 cm s ^-1处约为 86.8% ）。我们的研究结果支持这样的假设，即三叶虫的排队行为是减少水动力阻力的一种适应。这种减阻效应补偿了运动的能量成本，这在迁移过程中特别有利。