ABSTRACT Evidence of predator-prey interactions in the fossil record offers important insights into extinct ecosystems. As direct predator-prey relationships are rarely preserved, records of failed predation upon prey species are often considered. The biomineralized exoskeleton of trilobites is exemplary for recording injuries that have resulted from predation. Despite the extensive documentation of trilobite injuries, abnormal specimens are often documented in isolation, with examples of injuries among clustered individuals being poorly known. Here we document a well-preserved body cluster of 18 individuals of the large lichid trilobite Arctinurus boltoni from the mid-Silurian (Wenlock) Rochester Shale of New York, with eight specimens showing injuries. Landmark geometric morphometrics of the specimens is used to explore possible patterns between injured and noninjured specimens. Results of the morphometric analysis indicate that injured and noninjured specimens do not show any systematic difference in overall shape of the exoskeleton, but many of the larger specimens have injuries. The majority of injuries are posteriorly located and right-side dominant, highlighting the possibility of predator or prey lateralization. Biostratinomic evidence suggests that the cluster represents a biological aggregation that was rapidly buried in situ. Potential reasons for this gregarious behavior are discussed, including the possibility that individuals of A. boltoni grouped together to provide “safety in numbers” against predatory attack.

中文翻译：

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来自纽约志留纪罗切斯特页岩的三叶虫群：捕食模式和可能的防御行为

摘要 化石记录中捕食者-猎物相互作用的证据提供了对灭绝生态系统的重要见解。由于很少保留直接的捕食者-猎物关系，因此经常考虑捕食猎物物种失败的记录。三叶虫的生物矿化外骨骼是记录捕食造成的伤害的典范。尽管有大量关于三叶虫损伤的记录，但异常标本通常是单独记录的，集群个体受伤的例子鲜为人知。在这里，我们记录了来自纽约中志留纪 (Wenlock) 罗切斯特页岩的 18 个大型 lichid 三叶虫 Arctinurus boltoni 的保存完好的尸体群，其中 8 个标本显示受伤。标本的地标几何形态测量学用于探索受伤和未受伤标本之间可能的模式。形态测量分析的结果表明，受伤和未受伤的标本在外骨骼的整体形状上没有表现出任何系统性差异，但许多较大的标本都有损伤。大多数损伤位于后方且右侧占优势，突出了捕食者或猎物侧化的可能性。生物地层学证据表明，该簇代表了一种被迅速埋藏在原位的生物聚集体。讨论了这种群居行为的潜在原因，包括 A. boltoni 的个体聚集在一起以提供“数量安全”以抵御掠夺性攻击的可能性。形态测量分析的结果表明，受伤和未受伤的标本在外骨骼的整体形状上没有表现出任何系统性差异，但许多较大的标本都有损伤。大多数损伤位于后方且右侧占优势，突出了捕食者或猎物侧化的可能性。生物地层学证据表明，该簇代表了一种被迅速埋藏在原位的生物聚集体。讨论了这种群居行为的潜在原因，包括 A. boltoni 的个体聚集在一起以提供“数量安全”以抵御掠夺性攻击的可能性。形态测量分析的结果表明，受伤和未受伤的标本在外骨骼的整体形状上没有表现出任何系统性差异，但许多较大的标本都有损伤。大多数损伤位于后方且右侧占优势，突出了捕食者或猎物侧化的可能性。生物地层学证据表明，该簇代表了一种被迅速埋藏在原位的生物聚集体。讨论了这种群居行为的潜在原因，包括 A. boltoni 的个体聚集在一起以提供“数量安全”以抵御掠夺性攻击的可能性。大多数损伤位于后方且右侧占优势，突出了捕食者或猎物侧化的可能性。生物地层学证据表明，该簇代表了一种被迅速埋藏在原位的生物聚集体。讨论了这种群居行为的潜在原因，包括 A. boltoni 的个体聚集在一起以提供“数量安全”以抵御掠夺性攻击的可能性。大多数损伤位于后方且右侧占优势，突出了捕食者或猎物侧化的可能性。生物地层学证据表明，该簇代表了一种被迅速埋藏在原位的生物聚集体。讨论了这种群居行为的潜在原因，包括 A. boltoni 的个体聚集在一起以提供“数量安全”以抵御掠夺性攻击的可能性。