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Carnivorous sponges belonging to family Cladorhizidae (Porifera, Demospongiae, Poecilosclerida) are unique within phylum Porifera due to their ability to capture and envelop small prey. While other sponges use an aquiferous system to filter water, the aquiferous system of the cladorhizids is partially reduced or completely absent. Carnivorous sponges can be found worldwide at all depths, but are more common in the deep sea, where oligotrophic conditions containing less suspended particles may favor a carnivorous feeding strategy. Here, we provide formal descriptions of eight cladorhizid sponge species from 1229 to 5813 m depth collected as part of the NOAA 2016 Deepwater Exploration of the Marianas with the NOAA ship Okeanos Explorer (EX1605) during the investigation of the bathyal and abyssal seafloor off the Northern Mariana Islands and Guam: the harp sponge Chondrocladia (Symmetrocladia) lyra, Chondrocladia (Chondrocladia) coronata sp. nov., Lycopodina subtile sp. nov., Abyssocladia fryerae sp. nov., Abyssocladia kellyae sp. nov., Abyssocladia marianensis sp. nov., Abyssocladia stegosaurensis sp. nov., and Abyssocladia villosa sp. nov. We also provide a phylogenetic analysis showing the systematic position of the described species. Our results show that the deep-sea seafloor off the Mariana Islands contains a diverse and previously virtually unknown cladorhizid fauna. The examined species display similarities with species from other parts of the Pacific, and add considerably to the available information for the genus Abyssocladia. The high number of new species is consistent with other recent publications from the Pacific and Indian Ocean, and shows that despite recent sampling efforts, the cladorhizid fauna of these areas remains very poorly investigated. Additional sampling effort will in all probability yield both additional species and a better understanding of the biogeographical distribution of already known cladorhizids.Life Science Identifiers (LSIDs)Abyssocladia fryeraeurn:lsid:zoobank.org:act:BD7C52A3-146E-48CC-917F-57D7081245BD.Abyssocladia kellyaeurn:lsid:zoobank.org:act:7174B51E-5145-4907-AA63-D218C66DF5E7.Abyssocladia marianensisurn:lsid:zoobank.org:act:9761A542-C7F7-4449-BADD-E1F988454969.Abyssocladia stegosaurensisurn:lsid:zoobank.org:act:02F01ACE-2AC1-406E-8C50-65A5EC97F8C5.Abyssocladia villosaurn:lsid:zoobank.org:act:DAAA1ED2-5D36-40A3-9A78-55994 CDE9702.Chondrocladia coronataurn:lsid:zoobank.org:act:ED85F7AD-84F8-47EC-88E6-87753 AD931C4.Lycopodium subtileurn:lsid:zoobank.org:act:5F73AA9E-3182-49DD-8DD5-EDE501 C33E51.

Demosponges are challenging for phylogenetic systematics because of their plastic and relatively simple morphologies and many deep divergences between major clades. To improve understanding of the phylogenetic relationships within Demospongiae, we sequenced and analyzed seven nuclear housekeeping genes involved in a variety of cellular functions from a diverse group of sponges.We generated data from each of the four sponge classes (i.e., Calcarea, Demospongiae, Hexactinellida, and Homoscleromorpha), but focused on family-level relationships within demosponges. With data for 21 newly sampled families, our Maximum Likelihood and Bayesian-based approaches recovered previously phylogenetically defined taxa: Keratosa(p), Myxospongiae(p), Spongillida(p), Haploscleromorpha(p) (the marine haplosclerids) and Democlavia(p). We found conflicting results concerning the relationships of Keratosa(p) and Myxospongiae(p) to the remaining demosponges, but our results strongly supported a clade of Haploscleromorpha(p)+Spongillida(p)+Democlavia(p). In contrast to hypotheses based on mitochondrial genome and ribosomal data, nuclear housekeeping gene data suggested that freshwater sponges (Spongillida(p)) are sister to Haploscleromorpha(p) rather than part of Democlavia(p). Within Keratosa(p), we found equivocal results as to the monophyly of Dictyoceratida. Within Myxospongiae(p), Chondrosida and Verongida were monophyletic. A well-supported clade within Democlavia(p), Tetractinellida(p), composed of all sampled members of Astrophorina and Spirophorina (including the only lithistid in our analysis), was consistently revealed as the sister group to all other members of Democlavia(p). Within Tetractinellida(p), we did not recover monophyletic Astrophorina or Spirophorina. Our results also reaffirmed the monophyly of order Poecilosclerida (excluding Desmacellidae and Raspailiidae), and polyphyly of Hadromerida and Halichondrida.These results, using an independent nuclear gene set, confirmed many hypotheses based on ribosomal and/or mitochondrial genes, and they also identified clades with low statistical support or clades that conflicted with traditional morphological classification. Our results will serve as a basis for future exploration of these outstanding questions using more taxon- and gene-rich datasets.