Biannulata Samaai et al. 2006

Subgenus Biannulata Samaai et al. 2006

Type species. Latrunculia kaakaariki Alvarez, Bergquist and Battershill, 2002, here designated.

Diagnosis. Latrunculia species in which the anisodiscorhabd microscleres have only two whorls around the shaft, the median and subsidiary whorls, and these are located closer to the apical whorl than to the manubrium. The manubrium and basal whorl are indistinguishable, forming a cuff of irregularly distributed spines that are themselves lightly and irregularly spined. The apical whorl and apex are also indistinguishable, forming a tuft of irregularly distributed spines that are smooth or lightly and irregularly spined. The whorls are frequently composed of robust spines that are themselves lightly and irregularly spined, the primary spines are arranged horizontally around the shaft and may be grouped into sectors. The megascleres may be lightly and irregularly spined along the shaft (emended from Samaai et al. 2006).

Remarks. In L. (Biannulata) the basal progenitor emerges as a single, undifferentiated, irregularly distributed cuff of spines (see Alvarez et al. 2002: figs 2c, 4c, 5c, 6b, 6c, 7c), above which emerge the regularly distributed spines of the median and subsidiary whorls (Fig. 1, right). The apical progenitor emerges undifferentiated in most species, forming an irregularly distributed tuft of spines. The apex may or may not be defined (see also Alvarez et al., 2002: figs 2c, 4c, 5c, 6b, 6c, 7c; Samaai et al. 2004: fig 2).