Middle Permian marine invertebrate assemblages from Central Thailand are strongly dominated by gastropods. Two gastropod assemblages from the Tak Fa Limestone at Khao Noi and Khao Chao Thong of the Nakhon Sawan area are the first Permian ones from Thailand that are analysed regarding diversity and composition based on quantitative data. Both gastropod assemblages, comprising 40 species in total, are dominated by the gastropods Anomphalus sp., Warthia cf. brevisinuata and Glabrocingulum magnum; the genus Anomphalus is especially abundant which is unusual for Permian assemblages. Both studied gastropod assemblages have a similar taxonomic composition and diversity including the same values of diversity indices that indicate a moderate diversity. In addition, rarefaction analyses and rank-abundance distributions also suggest that diversity and structure of both assemblages are the same. The studied assemblage is compared with other Permian gastropod assemblages from Asia (Malaysia, East Timor and Japan). Rarefaction, diversity indices and rank-abundance distributions suggest that the diversity of the studied fauna is distinctly lower than that of the others despite coming from similar depositional environments. This is surprising because the Tak Fa gastropods lived at lower latitudes than the others. This could suggest an inverse diversity gradient in the Palaeo-Tethys, but more evidence is needed to substantiate this assumption. Several Late Palaeozoic and Early Mesozoic fossil assemblages are dominated by gastropods, e.g. those from the Pennsylvanian Buckhorn Asphalt deposit, the Permian from Japan and Malaysia, as well as the Late Triassic Cassian Formation. This shows that at least locally, gastropod dominance is not restricted to modern faunas.

来自泰国中部的中二叠纪海洋无脊椎动物组合主要由腹足动物主导。来自Nakhon Sawan地区的Khao Noi和Khao Chao Thong的Tak Fa石灰岩的两种腹足动物组合是泰国的第一批二叠纪组合，并根据定量数据对其多样性和组成进行了分析。两种腹足动物的组合，总共包括40种，由腹足动物Anomphalus sp。，Warthia cf.主导。灯盏花和大杯灯盏花; 羊草属特别丰富，这在二叠纪组合中是不常见的。两种研究过的腹足动物组合具有相似的分类学组成和多样性，包括表明中等多样性的相同多样性指数值。此外，稀疏度分析和等级丰度分布还表明两种组合的多样性和结构相同。将研究的组件与亚洲（马来西亚，东帝汶和日本）的其他二叠纪腹足动物组件进行了比较。回流，多样性指数和秩-丰度分布表明，尽管来自相似的沉积环境，但所研究动物的多样性明显低于其他动物。这是令人惊讶的，因为德发腹足类动物生活在比其他地区更低的纬度上。这可能暗示了古特提斯地区的反多样性梯度，但是需要更多的证据来证实这一假设。腹足动物主要是几种晚古生代和中生代化石组合，例如宾夕法尼亚州的巴克霍恩沥青矿，日本和马来西亚的二叠纪以及三叠纪的后加世组。这表明，至少在腹足纲动物的统治地位并不局限于现代动物区系。