Cyclacanthia

Genus Cyclacanthia n.g

Type species. Latrunculia bellae Samaai & Kelly, 2003: 14, Fig. 3 C, 4D, 5D.

Diagnosis. Thinly encrusting sponges with long cylindrical to tapering volcano­shaped oscular fistules and truncate areolate porefields, surface even, non hispid but felt­like to the touch, texture in life soft, compressible, only slightly compressible in preservative. Colour in life, emerald green to olive green and in preservative dark green to dark brownish green. Choanosomal architecture consists of broad swathes or defined tracts of megascleres (styles) that diverge and radiate from the base of the sponge towards the upper choanosome, where they form loose brushes and the typical whispy reticulation of other Latrunculiidae, with megascleres scattered interstitially; ectosome composed of a dense tangential layer of megascleres with an irregular palisade of microscleres at the surface that are oriented in many directions. Microscleres are acanthose isospinodiscorhabds with a straight stout shaft bearing identical apical whorl and basal manubrium with a reduced numbers of discrete conical spines that may be unevenly distributed around the shaft, i.e. grouped in bunches. The median whorl is equidistant from the apical whorl and manubrium, and bears several discrete conical spines; all spines are secondarily spinose. A single spike protrudes from the manubrium and apical whorls in the plane of the shaft. Microscleres are disposed in a palisade with their basal whorls buried in the outer ectosome.

Etymology. The name is derived from the Greek words cyclo meaning ring and acanthus meaning spine/thorn. Cyclacanthia refers to the arrangements of the spines around the shaft of the discorhabd (forming a ring of spines as oppose to a whorl).

Remarks. The microscleres in Cyclacanthia n.g. are acanthose isospino(acantho)discorhabd with a stout straight shaft bearing an apical whorl with a reduced number of spines, and a reduced spinose manubrium that are undifferentiated in the size and form of the constituent spines. The apical whorl and manubrium do not form a rosette structure where the spines merge to form a disc or crown­like structure, as in the anisodiscorhabds of Latrunculia or Sceptrella (see Fig. 2 in Samaai and Kelly, 2002), but the number of spines in the whorl is reduced considerably and they remain discrete and grouped. These microscleres superficially resemble the spinorhabds of Diacarnus Burton and Sigmosceptrella Dendy (Kelly & Samaai 2002), but differ from them in being secondarily spinose, and in their uneven (grouped) distribution around the shaft. A single spike protrudes from the manubrium and apical whorls. The median whorl is equidistant from the apical whorl and manubrium, and bears several discrete conical spines that may be acanthose.