The Ediacaran taxon Conotubus hemiannulatus has been discovered in the Terreneuvian blue clays of Estonia. Alongside Conotubus, Gaojiashania-like tubes are also found in these clays. These tubes are fully compressed and pyritized. The well-developed peristomes of Conotubus might have provided stability if the living worm was partially buried in the soft sea floor, suggesting that Conotubus was a sessile suspension feeder. The presence of the archaic Conotubus hemiannulatus in the Fortunian of Estonia indicates that the tube morphology of some cloudinids did not change between the Ediacaran and the Terreneuvian. The existence of these old-fashioned cloudinids in the Terreneuvian suggests either that the early Cambrian ecosystem in Baltica was not significantly different from that of the Ediacaran, or that cloudinids with organic tubes were more resilient to ecological changes than previously thought. Most Terreneuvian faunas originate from lower latitudes, whereas Baltica, during the Terreneuvian, was located at middle-high latitudes and experienced a cold climate. We hypothesize that the cold climate zone ecosystem was more archaic in the Fortunian than the tropical ecosystem, providing a final refuge for the Ediacaran non-mineralized tubicolous organisms. The increased competition pressure from diverse modern animals in the tropics could have driven Ediacaran-type non-mineralized tubicolous organisms to seek refuge in the colder regions of the ocean, where the competition from more advanced animals was less intense.

中文翻译：

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埃迪卡拉纪型非矿化管状生物在波罗的海持续到寒武纪早期（Terreneuvian）


埃迪卡拉纪分类群 Conotubus hemiannulatus 已在爱沙尼亚的 Terreneuvian 蓝色粘土中被发现。除了 Conotubus，在这些粘土中还发现了类似 Gaojiashania 的管。这些管子被完全压缩和热化。如果活的蠕虫部分埋在柔软的海底，那么 Conotubus 发达的口周可能提供了稳定性，这表明 Conotubus 是一种无柄悬浮食性动物。在爱沙尼亚的 Fortunian 中存在古老的 Conotubus hemiannulatus 表明，一些云科动物的管状形态在 Ediacaran 和 Terreneuvian 之间没有变化。这些老式的云鸥在特雷诺夫纪的存在表明，波罗的海早期寒武纪生态系统与埃迪卡拉纪的生态系统没有显著差异，或者具有有机管的云鸥对生态变化的适应能力比以前认为的要强。大多数特雷诺夫动物群起源于低纬度地区，而波罗的海在特雷纽夫时期位于中高纬度地区，气候寒冷。我们假设 Fortunian 的寒冷气候区生态系统比热带生态系统更古老，为 Ediacaran 非矿化管状生物提供了最终的避难所。热带地区各种现代动物增加的竞争压力可能促使埃迪卡拉纪型非矿化管状生物在海洋较冷的地区寻求庇护，那里与更高级动物的竞争不那么激烈。