We investigated the morphology and evolutionary relationships of Torodinium spp. and Katodinium glaucum, unarmoured dinoflagellates characterized by a small hyposome. An emended generic description of Torodinium was proposed based on light and scanning electron microscopy. Torodinium exhibited a unique combination of morphological features including a minute hyposome, a long episome with longitudinal ribs and a canal of unknown function on the dextro-lateral side. Unlike any known dinoflagellate both cingulum and sulcus extended in the episome. The apex surface showed ribs that converged in a bill-like projection. The shape of the apical groove was a circular spiral that extended around the apex running in 2.5 turns in an anticlockwise direction. The type species T. teredo was usually longer than T. robustum. The longitudinal outline of T. teredo was linear, with almost parallel margins, a circular transversal section, a relatively large hyposome and a conspicuous bill-like projection. The longitudinal outline of T. robustum was oblong, widened in the middle, with an ellipsoidal transversal section, a small hyposome and a less prominent bill-like projection. Several morphological features of Katodinium glaucum (=Gyrodinium glaucum) resembled Gyrodinium, such as the cingular displacement, longitudinal ribs, trichocysts, rod-shaped and refractile bodies and a capsule that surrounded the spherical nucleus. Distinctive features of K. glaucum were the horseshoe-shaped apical groove under a tongue-shaped notch pointed towards the dorsal side, and a bifurcated proximal end of the cingulum. Phylogenetic analysis revealed that Torodinium spp. and K. glaucum formed two independent lineages with no close relationships with other known dinoflagellates. The morphology of K. glaucum was distant from the type species of Katodinium. We propose the new genus and combination Lebouridinium glaucum gen. nov., comb. nov. for the species Katodinium glaucum.

中文翻译：

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带有小假体的无甲甲藻：Torodinium 和 Lebouridiniumgen。十一月 为 Katodinium glaucum (Gymnodiniales, Dinophyceae)

我们研究了 Torodinium spp 的形态和进化关系。和 Katodinium glaucum，无甲甲藻，特征为小假体。基于光学和扫描电子显微镜，提出了对 Torodinium 的修订通用描述。Torodinium 表现出独特的形态特征组合，包括微小的半体、带有纵向肋骨的长附加体和右外侧功能未知的管道。与任何已知的甲藻不同，扣带和沟都在附加体中延伸。顶点表面显示出会聚成喙状突起的肋。顶端凹槽的形状是一个圆形螺旋，围绕顶端沿逆时针方向以 2.5 圈延伸。模式种 T. teredo 通常比 T. robustum 长。T的纵向轮廓。teredo 呈线状，边缘几乎平行，横截面呈圆形，相对较大的半体和明显的喙状突起。T. robustum 的纵向轮廓呈长圆形，中间加宽，横截面呈椭圆形，有一个小的假体和一个不太突出的喙状突起。Katodinium glaucum (= Gyrodinium glaucum) 的几个形态特征与 Gyrodinium 相似，例如扣带移位、纵肋、毛囊、棒状和折射体以及围绕球形核的囊。K. glaucum 的显着特征是马蹄形顶槽位于舌形切口下方，指向背侧，以及扣带的分叉近端。系统发育分析表明，Torodinium spp。和K。glaucum 形成了两个独立的谱系，与其他已知的甲藻没有密切的关系。K. glaucum的形态与Katodinium的模式种相距甚远。我们提出了新属和组合 Lebouridinium glaucum gen。十一月，梳子。十一月 对于物种 Katodinium glaucum。