Mourellina decussata ( Harmer, 1926 ) Harmer, 1926

Reverter-Gil, Oscar, Souto, Javier & Fernández-Pulpeiro, Eugenio, 2011, Revision of the genus Crepis Jullien (Bryozoa: Cheilostomata) with description of a new genus and family and notes on Chlidoniidae, Zootaxa 2993, pp. 1-22 : 14-15

Mourellina decussata ( Harmer, 1926) n. comb.

( Figs 34–42 ; Table 8)

Crepis decussata Harmer, 1926: 320 , form a, pl. 15, figs 6–8.

Material examined. Lectotype: ZMA V.Bry. 1811, Crepis decussata erect form, Siboga Stn 227, western end of Ceram, Banda Sea, Indonesia, 13/11/1899, 2081 m, nº162 A 3, figured specimen, pl. 15, fig. 6 (slide). Paralectotypes: NHMUK 1928.3.6.121, Crepis decussata , part of type, same locality as lectotype, donated by S. Harmer (slide). ZMA V.Br. 875/3, Crepis decussata erect form a, type, nº 162 A, same locality as lectotype (in alcohol). ZMA Br. 1460, Crepis decussata erect form, type, nº162 A 2, figured specimen, pl. 15, figs 7, 8, same locality as lectotype (slide).

Description. Colony erect, lightly calcified, hydroid-like, composed of cylindrical stems with a strict growth pattern. Internodes straight, 2.7–3.2 mm long by 0.18 mm wide, jointed at their bases, consisting of four series of zooids, arranged in 3–7 (mean 5) alternate pairs. Zooids divided in two parts, proximal and distal. Proximal part adnate, tubular, very long, immersed in internode and joined to proximal zooid in same plane. Distal part projecting outwards at an acute angle from the axis; spoon-shaped, with extensive area of membranous frontal wall, facing proximally. Operculum terminal, with crescentic marginal sclerite. Cryptocyst small, transversely crescentic, its distal rim forming an upwardly curved lip; continuous with tubular section, projecting horizontally into body cavity of distal section. Spines absent. Communication via uniporous septula, one between zooids in the same series, and four lateral septula — a pair near the proximal extremity joining the medial-distal part of the preceding lateral zooids, and a pair in the medial-distal part, joining the proximal extremity of the lateral succeeding zooids. Polypide with few tentacles; retracted polypides not folded, lying almost entirely in proximal section, sometimes with tips of tentacles just extending into base of distal section. Mural spinules (and perhaps spicules) projecting into body cavity throughout zooid. Dichotomies dividing a branch of four series into two branches of two series; plane of bifurcation at right angle to last pair of zooids in internode. Each central zooid gives rise to a distal zooid, angled to right side in frontal view; each lateral zooid also angled to same side, forming a branch initially biserial. Each cauda producing another zooid from a lateral pore near its proximal end, distally deflected and closely applied to parent zooid so the branch becomes four-serial. Branches initially unjointed, soon developing yellowish joints. Avicularia with polypide, replacing a pair of autozooids, commonly the penultimate pair of an internode; similar to autozooids in size and general shape, but distal section not spoon-shaped, joining proximal section at more acute angle; mandible terminal, curved, subtriangular with basal sclerite, acicular terminally. Ancestrula and ovicell not known.

Erect section height 0.364 0.0225 0.304 0.391 16

SD, Standard deviation; N, number of measurements.

Figures

FIGURES 34 – 38. Mourellina decussata (Harmer, 1926) n. comb. (ZMA V. Bry. 1811, lectotype). 34, part of a colony; 35, a dichotomy; 36, 37, projecting portion of autozooids showing the cryptocyst; 38, a vicarious avicularium.

FIGURES 39 – 42. Mourellina decussata (Harmer, 1926) n. comb. 39, a dichotomy (ZMA Br. 1460, paralectotype); 40, same, lateral branching; 41, same, vicarious avicularia, showing the musculature; 42, internal mural spinules (ZMA V. Br. 875 / 3, paralectotype).