Hypnodinium

甲藻門Dinophyta

雙鞭藻綱Dinophyceae

植甲藻目 Phytodiniales

植甲藻科 Phytodiniaceae

厚甲藻屬Tetradinium

描述：Spherical, Planktonic, immobile, golden cell. Floating, nonmotile unicell; spherical; protoplast shows gymnondinioid organization (cingulum and sulcus, parietal plastids,eyespot) but there are no flagella; envelope closely appressed. This genus may be the cyst stage of a motile species, may be part of the history of Cystodinium (zygote), or may be valid since reproduction via aplanospores was observed.