We describe aggregative microconchid (Lophophorata) tubes from the uppermost Permian (upper Changhsingian) and Lower Triassic (Olenekian) lacustrine and fluvial strata of the Tunguska and Kuznetsk basins and the southern Cis-Urals, Russia. These attach to clam shrimp carapaces, bivalve shells, terrestrial plant fragments and a horseshoe crab head shield, and also form their own monospecific agglomerations. Planispiral tubes of a wide size range (0.1–2.5 mm) create dense settlements on these firm substrates, which likely comprise multiple generations of the same species. These finds confirm that this extinct lophophorate group was inhabiting non-marine continental basins during latest Permian and earliest Triassic time, when they were major suspension feeders in such limnic ecosystems. Microconchids dispersed extensively and rapidly in the aftermath of the Permian–Triassic mass extinction into both marine and continental basins at low and moderately high latitudes, which were notably different in salinity, temperature, depth and redox conditions. This confirms that small lightly calcified microconchids were a genuine disaster eurytopic group, whose expansion may have been promoted by low predator pressure and low competition for substrate.

中文翻译：

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来自独联体-乌拉尔和通古斯卡和库兹涅茨克盆地（俄罗斯）最上层二叠纪和下三叠统湖泊地层的灾害微贝

我们描述了来自通古斯卡和库兹涅茨克盆地以及俄罗斯独联体-乌拉尔南部的二叠纪（上长兴阶）和下三叠统（奥列内克阶）湖泊和河流地层的聚集性微贝（Lophophorata）管。它们附着在蛤虾甲壳、双壳贝壳、陆生植物碎片和鲎头盾上，也形成了它们自己的单特异性聚集体。宽尺寸范围（0.1-2.5 毫米）的平面螺旋管在这些坚固的基质上形成密集的沉降，这可能包括同一物种的多代。这些发现证实，在二叠纪晚期和三叠纪早期，这个灭绝的陆基生物群居住在非海洋大陆盆地，当时它们是这种边缘生态系统中的主要悬浮饲养者。在二叠纪-三叠纪大灭绝之后，微贝壳广泛而迅速地分散到低纬度和中高纬度的海洋和大陆盆地中，这些盆地在盐度、温度、深度和氧化还原条件方面存在显着差异。这证实了轻微钙化的小型微贝类是真正的灾难性普遍群体，其扩张可能是由于捕食者压力低和对基质的竞争低而促进的。