Specimen. BELUM.Mc 2015.308, cruise sample number NBP 1103 –DH 97 –sponge 10. 30 th May 2011 Sars Seamount, 59 ° 43.06 ’S 68 °. 52.23 ’W, 620–700m, Hein Dredge.
External morphology (Figure 2 A). Small fragment of pale brown sponge 5 by 2cm. Sponge body formed of an irregular meshwork of connected fibres, giving a lacy appearance. When dried, the sponge is white and the mesh is hard and brittle.
Skeleton (Figure 2 B). Very irregular framework of variable size triangular meshes 554 –(713)– 819 µm in max. length with a beam width 66 –(104)– 195 µm (up to 2mm in type), beams are smooth and nodes are smooth, not ornamented.
Spicules. Pentactins (Figure 2 C): entirely covered by small spines. Tangential ray 218 –(314)– 485 by 13 –(16)– 21 µm. Proximal ray 108 –(395)– 669 by 10 –(16)– 20 µm.
Discohexasters (Figure 2 D): diameter 44 –(54)– 70 µm, primary ray 2.9 –(5.2)– 7.9 µm, secondary ray 12.2 – (17.5)– 21.4 µm. Initially it seemed that there might be two size categories, measurements revealed that they were fairly evenly spread over the size range. Both spherical (in which the rays are regularly distributed around the radius) and stellate (where the rays form discrete clusters) forms were present, but as there were also intermediate forms we refrained from measuring these separately.
Rhopalasters (Figure 2 E): Total diameter 343 –(394)– 420 µm, primary ray 8.1 –(10.7)– 15.1 µm, secondary ray 168 –(192)– 206 µm. Between 5 and 7 (usually 6) secondary rays are present on each primary ray. Rays are spined, with large recurved spines on the second part of their length, and end in a disk.
Remarks. The rhopalasters correspond well in size and form with those of the type specimen: 300–400 µm in diameter with 6 terminal rays on short principal terminals. The discohexasters are within the same size range (measured by Reiswig & Kelly 2011 as spherical: 38–93 µm diameter and stellate 31–84 µm in diameter). The pentactins are of similar size (measured by Reiswig & Kelly 2011 as tangential ray length 191 –(281)– 384 µm, proximal ray length 313 –(450)– 560 µm). We did not find any oxyhexactins in our specimen, it is noted in the type description that these occur irregularly and the small size of our specimen may have resulted in them being missing.
Aulocalyx irregularis was originally described from 567m near Marion Island (Prince Edward Islands), SE of the Cape of Good Hope in the sub-Antarctic Indian Ocean. Other records are reported in Barthel & Tendal 1994, but Reiswig (2002) noted that they have probably been incorrectly identified due to an earlier assumption that any specimen with an irregular non-euretoid skeletal framework would be A. irregularis. In fact, without detailed examination of the full spiculation specimens can only be assigned to the family Aulocalycidae. The type location is the only previous record of A. irregularis, and the genus is is also known from two other locations in the Saya de Malha Group, W. Indian Ocean at depths of 567–915m (Reiswig 2002). A new species, Aulocalyx australis Reiswig & Kelly 2011 was recently described from Macquarie Ridge, Australia 676–1615m.