A new genus and species of freshwater sponge, Clypeatula cooperensis, collected from three lakes in the Northern Rocky Mountains of Montana, USA, are described. The sponge grows as a hard, disc‐shaped encrustation on the undersides of rocks and logs. It lacks microscleres and has amphioxeal megascleres that often show a slight midregion bulb and are usually covered with short, conical spines except at their tips. The sponge is also non‐gemmulating, overwintering in a regressed state in which choanocyte chambers are reduced in number. Phylogenetic analyses of complete 18S rDNA sequences of C. cooperensis, Ephydatia muelleri, Spongilla lacustris and Eunapius fragilis suggest that C. cooperensis is more closely related to Ephydatia muelleri than to Spongilla lacustris or Eunapius fragilis. Our data, nonetheless, do not rule out the possibility that C. cooperensis is more closely related to the non‐gemmulating sponges of Lake Baikal (Russia) than it is to Ephydatia muelleri. These phylogenetic analyses support the erection of a new genus, the monophyly of freshwater sponges belonging to the families Spongillidae and Lubomirskiidae, and the monophyly of demosponges.

中文翻译：

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Clypeatula cooperensis gen。n., sp. n.，来自美国蒙大拿州落基山脉的一种新的淡水海绵（Porifera，Spongillidae）

描述了从美国蒙大拿州北部落基山脉的三个湖泊收集的淡水海绵新属和种 Clypeatula cooperensis。海绵在岩石和原木的下面长成坚硬的圆盘状外壳。它没有微巩膜，并有两栖巨巩膜，通常显示出轻微的中间区域球茎，通常除了尖端外覆盖着短的圆锥形棘刺。海绵也是非宝石化的，在倒退状态下越冬，在这种状态下，尾骨细胞室的数量减少了。C. cooperensis、Ephydatia muelleri、Spongilla lacustris 和 Eunapius fragilis 的完整 18S rDNA 序列的系统发育分析表明，C. cooperensis 与 Ephydatia muelleri 的关系比与 Spongilla lacustris 或 Eunapius fragilis 的关系更密切。尽管如此，我们的数据并不排除 C. cooperensis 与贝加尔湖（俄罗斯）的非宝石海绵的关系比与 Ephydatia muelleri 的关系更密切。这些系统发育分析支持了一个新属的建立，即属于 Spongillidae 和 Lubomirskiidae 科的淡水海绵的单系，以及 demosponges 的单系。