The Tremadocian-to-Floian siliciclastic deposits of the Shirgesht Formation in the Kalmard Block of central Iran show abundant occurrences of the mid-tier Trichophycus venosus, a common ichnotaxon in the archetypical Cruziana ichnofacies. This trace fossil records a considerable increase in exploitation of offshore infaunal ecospace in comparison with older formations. Here, Trichophycus is relatively long and wide, with numerous and deep successively stacked causative burrows, which form dense burrow systems building the Crowded Trichophycus ichnofabric (CTI). Such development of CTI and the increase in depth of bioturbation had a negative effect on preservation of shallow-tier traces, for example arthropod burrows and trackways. This resulted in decreasing abundance of trilobite-produced trace fossils towards the top of the succession. The palaeobiological and palaeoecological interpretation of CTI points to stable habitats in muddy substrates above the storm wave base with high content of food and oxygen in pore waters, low-energy hydrodynamic regimes and a long colonization window. Moreover, the architecture and the morphological features of Trichophycus suggest a combined dwelling-feeding activity of the resident fair-weather producer showing the K-selected/climax strategy. The ethology of the producer, palaeoecological interpretations and taphonomic signatures revealed that it preferred dewatered, compacted muddy substrates (firmgrounds) in offshore settings, which might be related to minor hiatuses or short-lived discontinuities. Although the appearance of Trichophycus is concomitant to the earliest Cambrian agronomic revolution, it was uncommon until the early Ordovician, when locally it records infaunalization related to the Great Ordovician Biodiversification Event.

中文翻译：

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伊朗中部早期奥陶纪序列中拥挤的 Trichophycus ichnofabrics：洞察奥陶纪辐射

伊朗中部 Kalmard 地块 Shirgesht 组的 Tremadocian 至 Floian 硅质碎屑沉积物显示出大量的中层Trichophycus venosus 存在，这是原型Cruziana鱼相中的常见鱼类群。与较旧的地层相比，这种痕迹化石记录了对近海底栖生态空间的开发利用的显着增加。在这里，毛癣菌相对长而宽，有无数深连续堆积的致病洞穴，形成密集的洞穴系统，构成了拥挤的毛癣菌无机纤维（CTI）。CTI 的这种发展和生物扰动深度的增加对浅层痕迹的保存产生了负面影响，例如节肢动物洞穴和轨道。这导致在序列顶部的三叶虫产生的痕量化石的丰度减少。CTI 的古生物学和古生态学解释表明，风暴波底部上方泥质基质中的稳定栖息地，孔隙水中食物和氧气含量高，低能量水动力状态和长殖民窗口。此外，毛癣菌的结构和形态特征建议居民的晴天生产者的住宅-喂养联合活动显示 K-selected/climax 策略。生产者的行为学、古生态学解释和土壤埋藏学特征表明，它更喜欢近海环境中脱水、压实的泥质基质（坚硬地面），这可能与轻微的中断或短暂的不连续性有关。虽然毛癣菌的出现伴随着最早的寒武纪农艺革命，但直到奥陶纪早期才出现，当时它在当地记录了与大奥陶纪生物多样性事件相关的动物区系化。