Adreus, GRAY, 1867

Morrow, Christine, Cárdenas, Paco, Boury-Esnault, Nicole, Picton, Bernard, Mccormack, Grace, Soest, Rob Van, Collins, Allen, Redmond, Niamh, Maggs, Christine, Sigwart, Julia & Allcock, Louise A., 2019, Integrating morphological and molecular taxonomy with the revised concept of Stelligeridae (Porifera: Demospongiae), Zoological Journal of the Linnean Society 187, pp. 31-81 : 75-76

GENUS ADREUS GRAY, 1867

Emended diagnosis: Arborescent growth form; choanosomal skeleton with strongly compressed axis composed of long smooth tylostyles in bundles running longitudinally through branches; poorly developed extra-axial skeleton composed of sparse plumose brushes of smaller smooth styles ascending to periphery; euasters with curved or sinuous, smooth or spined, strongylote or tylote rays often branched, mainly confined to the ectosomal region, absent in some species.

Type species: Adreus fascicularis ( Bowerbank, 1866) .

Included species: Van Soest et al. (2018) listed three valid species: Adreus fascicularis ( Bowerbank, 1866) ; Adreus micraster (Burton, 1956) ; and Adreus stylifer (Arndt, 1927) . On the basis of molecular evidence presented in the Supporting Information ( Fig. S5), we formally propose the transfer of Raspailia (Parasyringella) australiensis Ridley, 1884 and Ceratopsion axiferum (Hentschel, 1912) to Adreus (see below, Adreus axiferum ).

Remarks: In addition to arborescent growth forms, we have also collected an undescribed encrusting Adreus (BELUM Mc4982); this species is represented in our 18S rRNA gene tree (Supporting Information, Fig. S2).

Erpenbeck et al. (2007), in an analysis of the systematics of Raspailiidae using partial 28S rRNA sequences, showed that Raspailia (Parasyringella) australiensis and Ceratopsion axiferum did not cluster with the main raspailiid group. In an attempt to resolve the taxonomic affinities of some of their ‘raspailiid’ taxa that failed to group with the main raspailiid clade, we combined many of their sequences with our own (Supporting Information, Fig. S5). Our analysis indicates that, rather than being raspailiids that have lost their acanthostyles, Raspailia (Parasyringella) australiensis and Ceratopsion axiferum are better interpreted as Adreus that have secondarily lost their asters. For these species, we propose the new combinations Adreus australiensis and Adreus axiferum .