For the first time gastropods from the Besano Formation (Anisian/Ladinian boundary) are documented. The material was collected from three different outcrops at Monte San Giorgio (Southern Alps, Ticino, Switzerland). The taxa here described are Worthenia (Humiliworthenia)? aff. microstriata, Frederikella cf. cancellata, ?Trachynerita sp., ?Omphaloptycha sp. 1 and ?Omphaloptycha sp. 2. They represent the best preserved specimens of a larger collection and document the presence in this formation of the clades Vetigastropoda, Neritimorpha and Caenogastropoda that were widespread on the Alpine Triassic carbonate platforms. True benthic molluscs are very rarely documented in the Besano Formation, which is interpreted as intra-platform basin sediments deposited in usually anoxic condition. Small and juvenile gastropods could have been lived as pseudoplankton attached to floating algae or as free-swimming veliger planktotrophic larval stages. Accumulations of larval specimens suggest unfavorable living conditions with prevailing disturbance in the planktic realm or mass mortality events. However, larger gastropods more probably were washed in with sediments disturbed by slumping and turbidite currents along the basin edge or storm activity across the platform of the time equivalent Middle San Salvatore Dolomite.

中文翻译：

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瑞士蒙特圣乔治贝萨诺组的中三叠纪腹足动物

首次记录了来自贝萨诺组（阿尼西亚/拉丁尼边界）的腹足动物。该材料是从Monte San Giorgio（瑞士提契诺州南阿尔卑斯山）的三个露头处收集的。这里描述的分类单元是Worthenia（Humiliworthenia）？aff。微小纹状体，腓特烈角cf. cancellata，Trachynerita sp。，Omphaloptycha sp。1和？Omphaloptycha sp。2.它们代表了保存最完好的大型标本，并记录了在三叠纪碳酸盐岩台地上广泛分布的维蒂加斯特罗波达，奈特里特莫塔和Caenogastropoda进化枝的存在。真正的底栖软体动物很少在贝萨诺组中得到记录，这被解释为通常在缺氧条件下沉积的平台内盆地沉积物。小型和幼年的腹足类动物可能以附着于浮藻的拟浮游生物或自由游动的浮游动物浮生幼虫阶段生活。幼虫标本的积累表明生活条件不利，在浮游生物领域或大规模死亡事件中普遍存在干扰。但是，较大的腹足动物更有可能被沉积物冲刷，这些沉积物会受到沿盆地边缘的塌陷和浊流的扰动，或者穿越相当于时空的中圣萨尔瓦多·白云岩平台的风暴活动。