Abstract Guadalupian (middle Permian) ichnoassemblages are described from the Mungadan Sandstone Formation (Kennedy Group), Merlinleigh sub-basin, Carnarvon Basin of Western Australia. In this formation, we recognize five facies (pebbly sandstone, intensely bioturbated sandstone, medium- to coarse-grained cross-stratified sandstone, fine-grained sandstone, and planar laminated siltstone), assigned to two facies associations, interpreted as the deposits of wave-dominated upper shoreface and lower shoreface settings. Ichnoassemblages, which contain 23 ichnospecies in 18 ichnogenera, are assigned to the Skolithos and Cruziana ichnofacies, as well as mixed types, and include representatives of cubichnia, repichnia, pascichnia, fodinichnia, domichnia, and agrichnia, indicating diverse trace-making behaviours. High burrow-density with monospecific occurrences of Skolithos indicate R-selected life strategies and burrow production over a short time period. The anomalous occurrence of Paleodictyon implies that the trace-making organisms of graphoglyptids could inhabit resource-rich shoreface environments as well as resource-limited deep sea niches. To better understand ichnological evolution across the Permian-Triassic (P-Tr) boundary, a database of Permian to Middle Triassic ichnoassemblages was also compiled for wave-dominated shoreface settings (WDSS) globally, and three ichno-ecological measures (ichnodiversity, ethological category, and ichnodisparity) were evaluated. Ichnodiversity shows a stepwise decline in ichnotaxa through the Permian, a pronounced increase in the Early Triassic, and a second phase of decline towards the Middle Triassic. Ethological data exhibit a different trend, with mean and median values dramatically dropping to a late Permian nadir, followed by a significant increase across the P-Tr boundary, culminating in an Early Triassic acme. The globally depauperate nature of late Permian ichnoassemblages may reflect sampling bias or decreased preservation potential resulting from abundant benthos and well-developed mixed layer in the seafloor. The presence of anomalously diverse Early Triassic ichnoassemblages may be due to the WDSS habitat providing a ‘habitable zone’ for trace-making organisms to survive when most marine environments were stressful in the aftermath of the P-Tr mass extinction. We emphasise that caution is needed in interpreting ichnodiversity variations across the P-Tr mass extinction event, as it may reflect shifting of trace-making behaviours of the same animals, or replacement of different animals with the same behaviours.

中文翻译：

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来自西澳大利亚卡那封盆地的中二叠纪遗迹化石组合：对跨越二叠纪-三叠纪边界的以波浪为主的硅质碎屑岩岸面环境中鱼类群落演化的意义

摘要 Guadalupian（中二叠纪）地层组合描述于西澳大利亚 Carnarvon 盆地 Merlinleigh 子盆地的 Mungadan 砂岩组（肯尼迪集团）。在该地层中，我们识别出 5 个相（卵石砂岩、强烈生物扰动砂岩、中粗粒交错层理砂岩、细粒砂岩和平面层状粉砂岩），分为两个相组合，解释为波浪沉积- 主导的上岸面和下岸面设置。Ichnoassemblages 包含 18 个 ichnogenera 中的 23 个 ichnospecies，被分配到 Skolithos 和 Cruziana ichnofacies 以及混合类型，包括cubbhnia、repichnia、pascichnia、fodinichnia、domichnia 和 agrichnia 的代表，表明不同的痕迹制作行为。Skolithos 单种出现的高洞穴密度表明 R 选择的生活策略和短期内的洞穴生产。Paleodictyon 的异常发生意味着，graphoglyptids 的踪迹生物可以栖息在资源丰富的海岸环境以及资源有限的深海生态位。为了更好地了解跨越二叠纪-三叠纪 (P-Tr) 边界的地层演化，还针对全球波浪主导的岸面环境 (WDSS) 和三种地层生态措施（地层多样性、生态学类别）编制了二叠纪至中三叠纪地层组合数据库，和 ichnodisparity) 进行了评估。物种多样性显示鱼目群在二叠纪阶段逐步下降，早三叠世显着增加，中三叠世第二阶段下降。行为学数据显示出不同的趋势，均值和中值急剧下降到二叠纪晚期的最低点，随后在 P-Tr 边界显着增加，最终达到早三叠世的顶点。二叠纪晚期鱼类组合的全球退化性质可能反映了采样偏差或由于海底丰富的底栖动物和发育良好的混合层而导致的保存潜力下降。异常多样的早三叠世 ichnosemblages 的存在可能是由于 WDSS 栖息地为追踪生物提供了一个“宜居带”，当大多数海洋环境在 P-Tr 大灭绝之后处于压力状态时。我们强调在解释 P-Tr 大灭绝事件中的物种多样性变化时需要谨慎，