A new silicified Middle Permian gastropod fauna is reported from Central Thailand. It is the first diverse Permian gastropod assemblage described from the Sibumasu terrane. The gastropod fauna comes from fore-reef shallow water carbonates of the Middle Permian (Wordian) limestones of the Ratburi Group exposed at Khao Phrik, Ratchaburi Province. Thirty-four gastropod species are reported, 17 nominate species and 17 in open nomenclature. Nine species are new to science: Retispira khaophrikensis, Amaurotoma? multispirata, Eoplatyzona ratchaburiensis, Hesperiella cyrtocostata, Worthenia? waterhousei, Stegocoelia centrosinuata, Procerithium? inaequetuberculata, Chlorozyga asiatica and Hyphantozyga? khaophrikensis. The gastropod assemblage is strongly dominated by bellerophontids (especially Warthia and Retispira). The fauna shares only a few species with faunas from other Permian deposits in Thailand and elsewhere, namely the previously described gastropod fauna of the Tak Fa Limestone. The fauna shows relationships to Late Palaeozoic gastropod faunas from the Palaeo-Tethys, such as those of Australia and Malaysia.

中文翻译：

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来自泰国中部考披克的Ratburi石灰石的二叠纪腹足动物

泰国中部据报道有一种新的硅化的中二叠纪腹足动物群。这是从Sibumasu地貌中描述的第一个多样化的二叠纪腹足动物组合。腹足类动物区系来自叻uri府拉佛里地区暴露的Ratburi群中二叠世（Wordian）石灰岩的前礁浅层碳酸盐岩。据报道，腹足纲动物有34种，提名种有17种，开放命名法有17种。九种是新的科学物种：Retispira khaophrikensis，Aaurotoma？multispirata，Eoplatyzona ratchaburiensis，Hesperiella cyrtocostata，Worthenia？waterhousei，Stegocoelia centrosinuata，Procerithium？inaequetuberculata，Chlorozyga asiatica和Hyphantozyga？khaophrikensis。腹足动物的组合主要由风铃虫（尤其是Warthia和Retispira）主导。该动物群与泰国和其他地方的其他二叠纪沉积物的动物群仅有少数物种，即先前描述的达发石灰石的腹足动物群。该动物群显示了与古特提斯（例如澳大利亚和马来西亚）的晚古生代腹足动物群的关系。