Spiniflabellum spinosum ( Canu & Bassler, 1928 ) Canu & Bassler, 1928

Martino, Emanuela Di & Rosso, Antonietta, 2015, Revision of the bryozoan genus Gephyrotes Norman, 1903 (Cheilostomata, Cribrilinidae) with the description of two new taxa, Zootaxa 3941 (2), pp. 261-283 : 278-280

Spiniflabellum spinosum ( Canu & Bassler, 1928) n. comb.

( Figs 41–44 ; Table 9 )

Gephyrotes spinosum Canu & Bassler 1928: 29 –30, pl. 4, fig. 11.

Material examined: Holotype: USNM 7508, encrusting stones, Recent, north of Cuba.

Description: Colony encrusting, multiserial, unilaminar ( Fig. 41 ). Ancestrula and early astogeny not observed. Pore-chamber windows visible along zooidal margins at colony growing edge ( Figs 42, 44 ), at least four in the distal and four in the lateral walls, oval to subcircular (L = 25–33 µm; W = 40–55 µm), surrounded by a thin rim of calcification. Autozooids distinct with deep interzooidal furrows, elliptical ( Fig. 43 ), longer than broad (mean L/W = 1.54), quincuncially arranged. Frontal shield slightly convex, formed by 16–18 narrow (25–35 µm) pinnate costae, each separated by 8 elliptical, very minute (averaging 10 µm in length) intercostal pores. Costae converging and fused at zooidal midline; on each costa, three prominent, tubular pelmatidia, 30–45 µm long, 15–20 µm in diameter and slightly flared at the tip, conferring a characteristic thorny aspect to the frontal shield ( Figs 42, 44 ). Distalmost pair of costae broader (47–52 µm), smooth, bifurcating, the anterior bifurcations converging across orifice, forming a wide arch and bat-shaped pseudospiramen, obscuring the primary orifice from frontal view ( Fig. 43 ); the arch bears 5 hollow pelmatidial spines, adjacent pairs sometimes coalescent; two additional hollow spines from the proximal margin of the costa projecting into the pseudospiramen. Primary orifice semicircular ( Figs 42, 44 ), broader than long (80 x 133 µm), with concave proximal margin. Two or three platy elements each terminating in 2 to 4, coalescent, hollow spines, forming a flabellate structure overarching the orifice. Adventitious avicularia small (50–55 µm), pedunculate, paired, on distolateral corners of bifurcated costae; rostrum acutely triangular, distolaterally directed, pivot bar absent ( Fig. 43 ). Ooecia and kenozooids not observed.

N, Number of colonies and number of zooids measured; SD, standard deviation.

Remarks. This species is characterized by the simultaneous presence of a broad, robust pair of bifurcations of the distalmost costae, pedunculate adventitious avicularia associated with the orifice, a flabellate distal palisade of coalescent hollow spines, and tubular pelmatidia conferring to the frontal shield its spinose aspect. Canu & Bassler's (1928) original description reported the absence of ooecia. This statement has been confirmed by new SEM images. Hence, either the ooecia have not yet been found or S. spinosum lacks ooecia and has internal brooding.

Distribution. Recent, north Cuba and Straits of Florida, at a depth of 102–262 m from a grey coral and coral sand.

Figures

FIGURES 41 – 44. Spiniflabellum spinosum Canu & Bassler, 1928 n. comb., holotype, USNM 7508, Recent, north of Cuba: 41, general aspect of the colony; 42, zooids at the growing edge showing the formation and refief of the oral structures; 43, closeup of zooids, showing complete collar-like oral structures and paired, distal flabellate spines; note the pedunculate lateral avicularia (lacking pivot bars) associated with the costae, and the bat-shaped pseudospiramen; 44, peripheral autozooids showing basal pore chambers and the tubular pelmatidia in profile; a primary orifice is exposed, inclined relative to the frontal surface. Scale bars: Fig. 41, 500 Μm; Figs 42 – 44, 200 Μm.

Tables

TABLE 9. Measurements (in Μm) of Spiniflabellum spinosum (Canu & Bassler, 1928) n. comb., holotype, USNM 7508.

	N (colonies, zooids)	Mean	SD	Range
Zooid length	1, 10	500	49	451–577
Zooid width	1, 10	324	18	299–353
Avicularia length	1, 8	54	4	50–63
Avicularia width	1,8	33	4	28–37