ABSTRACT Thecadinium ovatum is one of the four species of Thecadinium sensu lato which has no apical pore, but has a ventral pore on the first apical plate, an unusual ‘multi-pimple-plate’ in the precingular series, and an antapical plate with several spines. Its original thecal plate formula was 3ʹ 6ʹʹ 6c 5s? 5ʹʹʹ 1ʹʹʹʹ. Morphological examination of cells from the Sea of Japan showed that T. ovatum has four apical plates and that the multi-pimple-plate is an anterior intercalary plate. The revised thecal plate formula of the species is 4ʹ1a 5ʹʹ6c 6s 5ʹʹʹ1ʹʹʹʹ. Molecular genetic data of T. ovatum were obtained for the first time. LSU rRNA gene sequences obtained by a single-cell PCR method from natural samples were used for taxonomic and phylogenetic studies. The sequence for T. ovatum did not show a close phylogenetic relationship to sequences of T. yashimaense, T. kofoidii and T. pseudokofoidii. The phylogenetic analysis of the D1/D2 and D8/D10 regions of the large subunit (LSU) rRNA from single cells indicated that Thecadinium ovatum formed the nearest sister branch to the Protoceratiaceae, including Pentaplacodinium usupianum, Pentaplacodinium saltonense, Protoceratium reticulatum, and Ceratocorys species. This clade was placed within the order Gonyaulacales. Consequently, T. ovatum does not belong to Thecadinium sensu stricto, nor does it show a phylogenetic relationship with other Thecadinium sensu lato species (T. yashimaense and Psammodinium inclinatum). Thus, T. ovatum should be transferred to an independent new genus that may be created after genetic information is available for the other morphologically close species.

中文翻译：

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俄罗斯太平洋沿岸卵壳藻（Dinophyceae）的形态学和系统发育

摘要 Thecadinium ovatum 是 Thecadinium sensu lato 的四种物种之一，它没有顶孔，但在第一顶板上有一个腹孔，前扣板系列中有一个不寻常的“多疙瘩板”，以及一个带有几个刺。它的原始鞘板公式是 3ʹ 6ʹʹ 6c 5s? 5ʹʹʹ·1·1ʹʹʹ1ʹ·1。来自日本海的细胞的形态学检查表明，T. ovatum 有四个顶端板，多丘疹板是一个前嵌板。该物种的修订后的鱼鳞板公式是4ʹ1a·5ʹʹ6c·6s·5ʹʹʹ1ʹʹʹ1ʹʹ1阿。首次获得T. ovatum的分子遗传数据。通过单细胞 PCR 方法从天然样品中获得的 LSU rRNA 基因序列用于分类学和系统发育研究。T 的序列。ovatum 与 T. yashimaense、T. kofoidii 和 T. pseudokofoidii 的序列没有表现出密切的系统发育关系。来自单细胞的大亚基 (LSU) rRNA 的 D1/D2 和 D8/D10 区域的系统发育分析表明 Thecadinium ovatum 形成了与原角藻科最近的姐妹分支，包括 Pentaplacodinium usupianum、Pentaplacodinium saltonense、Protoceratium species reticulatum 和 Ceratocorys . 这个进化枝被放置在 Gonyaucales 目内。因此，T. ovatum 不属于 Thecadinium sensu stricto，也不显示与其他 Thecadinium sensu lato 物种（T. yashimaense 和 Psammodinium inclinatum）的系统发育关系。因此，T。