The Symbiodiniaceae are a family of marine dinoflagellates known mostly for their endosymbiotic interactions with invertebrates and protists, but facultatively and exclusively free‐living life histories in this family are also evident. A recent systematic revision of the Symbiodiniaceae replaced the clade‐based nomenclature of seven divergent lineages of “Symbiodinium” sensu lato with one based on formally described genera. The revised taxonomy was not extended to the whole group because type species to describe a new genus for each of the remaining clades and subclades were lacking. In an effort to characterize benthic habitats of symbiodiniaceans in sediments at Heron Island (Great Barrier Reef, Australia), we isolated >100 monoclonal Symbiodiniaceae cultures. Four of these belonged to Symbiodiniaceae ‘subclade’ Fr3, and three to Clade H, based on nucleotide sequence similarity (ITS2, LSU, cp23S, and mtCOB), representing the first cultures of these taxa. Based on these isolates, we propose two new genera: Freudenthalidium gen. nov. and Halluxium gen. nov., circumscribing Clades Fr3 and H, respectively. Three new species are described: Freudenthalidium heronense, F. endolithicum, and Halluxium pauxillum. Kofoidian tabulations of motile cells confirm previous observations that amphiesmal vesicle arrangements are generally conserved across the family. These descriptions are an important step toward completing the systematic revision of the Symbiodiniaceae. That this contribution was enabled by isolates from an endopsammic habitat highlights the potential of discovering new symbiodiniacean species in the environment, the study of which will lead to a deeper understanding of free‐living versus symbiotic life histories in this ecologically important family of dinoflagellates.

中文翻译：

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说明弗洛伊登氏假体。十一月 和Halluxium gen。十一月 正式将进化枝Fr3和H识别为共生双齿科（Dinophyceae）的属。

共生恐龙科是一类海洋鞭毛藻，主要以与无脊椎动物和原生生物的共生共生作用而闻名，但在该家族中，兼性和完全自由生活的生活史也很明显。最近对共生植物的系统修订，取代了“共生素”的七个不同谱系的进化枝命名法sensu lato带有一个基于正式描述的属。修订后的分类法并未扩展到整个群体，因为缺少用于描述其余进化枝和亚进化枝的每个新属的类型物种。为了表征苍鹭岛（澳大利亚大堡礁）沉积物中共生双齿纲动物的底栖生境，我们分离了100种以上的共生双齿纲科细菌。基于核苷酸序列相似性（ITS2，LSU，cp23S和mtCOB），其中四个属于共生双歧杆菌“亚群” Fr3，三个属于进化枝H，代表了这些分类群的首批培养物。基于这些分离物，我们提出了两个新属：科氏杆菌属。十一月 和Halluxium gen。十一月，分别限制了Clades Fr3和H。描述了三个新物种：Herudense的Freudenthalidium heronense，F. endolithicum和Palillillum的Halluxium。运动细胞的Kofoidian列表证实了先前的观察，即在整个家庭中，两性小泡的排列通常是保守的。这些描述是朝着共生植物的系统修订的重要一步。这种贡献是由内窥镜细菌栖息地的分离物促成的，这突显了在环境中发现新的共生双菌纲物种的潜力，对其进行的研究将使人们更加深入地了解这一具有重要生态意义的鞭毛虫家庭的自由生活与共生生活史。