Didiscus Dendy, 1922 and Myrmekioderma Ehlers, 1870 are closely related genera of axinellid sponges, distinguished mainly by the presence of didiscorhabd microscleres in Didiscus and of trichodragmata in Myrmekioderma. Their family-level classification, however, is highly controversial, in part because their specific and morphological diversities are still poorly known. Here, we redescribed Didiscus oxeatus Hechtel, 1983 based on new specimens and revision of the holotype, described two new species of Didiscus and two new species of Myrmekioderma from off the Amazon and São Francisco river mouths in Northern and Northeastern Brazil. These two areas in the Tropical Atlantic (TA) are still understudied, especially when considering their high environmental and economic importance. We observed for the first time the presence of tylostyles in the holotype of D. oxeatus, as well as in the new specimens from Sergipe State. Didiscus pseudoverdensis sp. nov. has thick, strongly spined didiscorhabds with sharp ends; Didiscus raraediscus sp. nov. has small microspined oxeas; Myrmekioderma guajajara sp. nov. has microxeas and verrucose small oxeas; and Myrmekioderma tenax sp. nov. has both raphidiform and sinuous oxeas. The morphological diversities of both genera are expanded by the addition of new spicule types and ornamentations. Morphological data indicated that both Didiscus and Myrmekioderma should be classified in the family Heteroxyidae, in contrast to previous molecular studies, which suggest that they could belong at least in part to Raspailiidae. These two families and the genus Myrmekioderma are probably polyphyletic and need revision. The number of species of Didiscus and Myrmekioderma worldwide is raised to 11 and 13, respectively, of which five species of Didiscus and six of Myrmekioderma occur in the TA. Most species have narrow distributions, probably reflecting the low sampling effort. This study provides a more accurate picture of the biodiversity and distribution of Didiscus and Myrmekioderma in the TA and reinforces the importance of scientific explorations in understudied areas such as off the mouths of the Amazon and São Francisco rivers.

Didiscus Dendy（1922年）和Myrmekioderma Ehlers（1870年）是纺锤形海绵的近缘属，主要区别在于Didiscus中存在迪迪斯科哈伯微菌，而Myrmekioderma中存在毛滴虫。但是，它们的家族分类存在很大争议，部分原因是它们的具体和形态多样性仍然鲜为人知。在这里，我们根据新标本和整型的修订，重新描述了Didiscus oxeatus Hechtel，1983，描述了Didiscus的两个新物种和Myrmekioderma的两个新物种。来自巴西北部和东北部的亚马逊河和圣弗朗西斯科河口。在热带大西洋地区（TA）的这两个区域仍处于研究不足状态，尤其是考虑到它们在环境和经济方面的重要性时。我们首次观察到在D. oxeatus的原型中以及在Sergipe State的新标本中存在tylostyle 。Didiscus pseudoverdensis sp.。十一月 具有厚的，强力旋转的didiscorhabds，具有锋利的末端；Didiscus raraediscus sp。十一月 微小的微旋毛虫 桃金娘（Myrmekioderma guajajara sp。）十一月 有小micro虫和小毛ver。和腱霉菌sp。十一月 既有睫毛状又有弯曲的牛气菌。通过添加新的针尖类型和装饰物，扩大了两个属的形态多样性。形态学数据表明，与以前的分子研究相反，双歧杆菌和异种皮霉菌都应该归入杂种科，这表明它们可能至少部分属于Raspailiidae。这两个家族和Myrmekioderma属可能是多系的，需要修改。的种类的数目Didiscus和Myrmekioderma全世界被升高到分别为11和13，其中五个种的Didiscus和六个Myrmekioderma发生在TA中。大多数物种的分布较窄，可能反映了采样工作量低。这项研究提供了更精确的描绘了TA中Didiscus和Myrmekioderma的生物多样性和分布的信息，并强调了在诸如亚马逊河和圣弗朗西斯科河口等未充分研究的地区进行科学探索的重要性。