The Early Permian (Kungurian) Khao Khad Formation of Central Thailand consists mostly of carbonates deposited on the western margin of the Indochina Terrane. This formation has yielded unusual microbial-fusulinid limestones with large gastropods which contribute most to the rock volume. With a height of more than 6 cm, the gastropods are amongst the largest Early Permian gastropods ever reported. Gastropods as major rock formers are rare in the Palaeozoic. This, and other recently reported invertebrate faunas from Thailand show that gastropods may dominate Permian fossil assemblages not only in diversity, but also regarding abundance and in some cases also regarding biomass. Besides gastropods, fusulinids, various calcareous algae, intraclasts and thick microbial-cyanobacterial ( Girvanella and Archaeolithoporella ) coatings and reticular microbial patches as well as thick inter- and intragranular radial fibrous cement crusts are present. The gastropods represent at least four species and belong probably to undescribed taxa. The fusulinid genus Pseudofusulina and Misellina ( M .) termieri are reported from the Khao Khad Formation for the first time and indicate a Bolorian age. Calcareous algae are dominated by dasycladaceans followed by gymnocodiaceans and solenoporaceans. The studied limestone almost completely lacks metazoan reef builders such as corals and sponges. Likewise, brachiopods and bivalves are absent in the studied samples and echinoderms are very scarce. The carbonate is interpreted as product of shallow water, back-reef lagoonal platform community with a high productivity providing the large gastropods with sufficient food. However, conditions were too eutrophic for sessile filter feeders including metazoan reef builders.

中文翻译：

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带有大型腹足动物和钙质藻类的微生物、梭状石灰岩：来自泰国中部早二叠世 Khao Khad 地层的不寻常相

泰国中部的早二叠世 (Kungurian) Khao Khad 组主要由沉积在印度支那地体西缘的碳酸盐岩组成。该地层产生了具有大腹足动物的不寻常的微生物-梭菌石灰岩，这些腹足动物对岩石体积贡献最大。腹足类动物的高度超过 6 厘米，是有史以来报道的最大的早二叠世腹足类动物之一。腹足动物作为主要的岩石形成物在古生代很少见。这个，以及最近报道的其他来自泰国的无脊椎动物群表明，腹足类动物可能不仅在多样性方面，而且在丰度方面，在某些情况下还涉及生物量方面，可能在二叠纪化石组合中占主导地位。除了腹足类、梭菌类、各种钙质藻类，存在碎屑和厚的微生物蓝藻（Girvanella 和 Archaeolithoporella）涂层和网状微生物斑块以及厚的颗粒间和颗粒内径向纤维水泥结壳。腹足类动物至少有四种，可能属于未描述的分类群。fusulinid 属 Pseudofusulina 和 Misellina (M.) Terieri 是首次从 Khao Khad 组报道，表明它们属于 Bolorian 时代。钙质藻类以 dasycladaceans 为主，其次是裸藻纲和孔甲纲。所研究的石灰岩几乎完全没有珊瑚和海绵等后生生物礁建造者。同样，所研究的样本中不存在腕足动物和双壳类动物，棘皮动物非常稀少。碳酸盐被解释为浅水的产物，具有高生产力的后礁泻湖平台群落为大型腹足动物提供充足的食物。然而，对于包括后生动物珊瑚礁建造者在内的无柄滤食性动物来说，条件过于富营养化。