In many marine littoral and sublittoral benthic habitats, we find small diatoms with few features resolvable with light microscopy (LM) other than internal costae across their valves. While classically those internal costae have defined their identification and classification, the use of electron microscopy and of molecular data have started to reveal the true diversity of unrelated forms and genera (e.g., Anaulus, Eunotogramma, Hustedtiella, or Plagiogramma) which possess these structures. Here we describe the new genus Ambo, in an attempt to clarify some of the polyphyly of taxa with internal costa by formally transferring Anaulus balticus, Anaulus simonsenii, and Plagiogramma tenuissimum as well as Ambo gallaeciae, described here. Related to this, we attempt to document and characterize the genus Anaulus itself, which was formally described by Ehrenberg with an illustration. A search by LM of mica designated by Ehrenberg as the holotype of Anaulus scalaris, the generitype of Anaulus, failed to recover a specimen which adequately describes the genus to the exclusion of other genera with internal costa. We also present morphological and molecular data for Anaulus creticus and suggest a new genus—Ceratanaulus—to reflect the distinct morphological and molecular characters we documented.

在许多海洋滨海和滨海底栖生境中，我们发现小型硅藻几乎没有特征，而除了跨过其瓣膜的内部肋骨，这些特征可以用光学显微镜（LM）分辨。传统上，那些内部肋骨已定义了它们的识别和分类，但电子显微镜和分子数据的使用已开始揭示具有这些结构的无关形式和属（例如无名氏，古猿，马鞭草或Pla虫）的真实多样性。在这里，我们描述了新属安博，企图通过正式转移到澄清一些内部科斯塔类群的多元性的Anaulus balticus，Anaulus simonsenii以及此处描述的Pla虫（Pgigiogramma tenuissimum）和没食子虫（Ambo gallaeciae）。与此相关的是，我们尝试记录和描述Anaulus属本身，并由Ehrenberg对其进行了正式描述。LM搜寻由埃伦贝格（Ehrenberg）指定为无名氏无名氏（Anaulus scalaris）的全称的云母，未能找到足以充分描述该属的标本，以排除其他属有内部肋缘的属。我们还提供了无脊椎动物的形态和分子数据，并提出了一个新的属–角尾蛇（Ceratanaulus），以反映我们记录的独特的形态和分子特征。