Gephyrotes nitidopunctatus ( Smitt, 1868 )

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 : 263-265

Gephyrotes nitidopunctatus ( Smitt, 1868)

( Figs 2–8 ; Table 1 )

Escharipora figularis forma nitido-punctata Smitt 1868: 4, pl. 24, figs 2–3.

Cribrilina nitidopunctata: Smitt 1873: 22 ; Levinsen 1909: 159; Waters 1923: 564, pl. 18, figs 4–5; 1926: 438; Ryland 1963: 4. Gephyrotes nitidopunctata: Norman 1903: 101 , pl. 8, figs 12–13; Nordgaard 1906: 84, pl. 1, fig. 7; 1917: 50; Canu & Bassler 1920: 300, figs 81E, 85; 1929: 109, fig. 25; Lang 1922: 25, fig. 9; Prenant & Bobin 1966: 585, fig. 203; Kluge 1975: 468, fig. 246; Hayward & Ryland 1998: 316, fig. 111.

Material examined. Holotype: SMNH 1770, Recent, Finnmark, northern Norway, encrusting a stone.

Description. Colony unilaminar, multiserial, forming small irregular patch ( Fig. 2 ). Ancestrula not observed; early autozooids similar to later ones but smaller ( Fig. 2 ). Autozooids distinct, with deep interzooidal furrows, oval (mean L/W = 1.67), longer than broad. Gymnocyst smooth, narrow laterally, more extensive proximally; sometimes long 'tails' of gymnocyst developing proximally, giving zooid an irregular, elongated shape. Frontal shield relatively flat, formed by 8–12 costae, more often 9 ( Figs 3, 5 ), not including two distalmost pairs participating in proximal peristomial complex. Costae 40–55 µm broad, widely separated by 2 intercostal pores, the peripheral one transversely elongated for two-thirds of costal length (50 µm), the central one much smaller (20 µm) and subcircular; 2 large circular pelmatidia on each costa. Proximal peristomial complex formed by conjunction of 2 elevated distalmost pairs of costae, one pair originating lateral to orifice, the second pair with elevated anterior bifurcations ( Fig. 7 ). This complex generally with a semilunar intercostal lacuna (80–90 µm) and 2 elliptical lateral ones (55–65 µm) ( Fig. 7 ). Primary orifice broader than long (130 x 200 µm), semicircular ( Fig. 8 ); secondary orifice elliptical. Paired oral spines restricted to small periancestrular zooids ( Fig. 5 ). Adventitious avicularia large, usually paired, sometimes single or absent, placed lateral to orifice, proximally directed, rounded-triangular or curved, with complete pivot bar ( Fig. 4 ). Ooecium subglobular, prominent, almost as long as broad (205 x 216 µm), smooth, becoming immersed in distal zooid and covered by extension of its proximal gymnocyst, leaving exposed irregular patches of ovicell calcification ( Fig. 4 ). Kenozooids of two types: frequent tubular kenozooids of smooth gymnocyst, with openings of irregular size and shape, that often obscure zooidal boundaries ( Figs 3–4 ); rare elongate kenozooids with smooth extensive gymnocyst proximally and distally, having a frontal shield formed by 4 widely spaced costae with a single pelmatidium in each ( Fig. 8 ). Interzooidal communications via uniporous mural septula in vertical walls ( Fig. 6 ).

Remarks. One of the most peculiar features of this species, although overlooked or interpreted as thick secondary calcification, is the presence and development of tubular kenozooids, surrounding and obliterating zooidal boundaries by filling the furrows between zooids. The limits of single kenozooids along the network are undefined. Often they have more than one frontal opening; some resemble small triangular avicularia, mostly distally oriented, and closed by membranes not mandibles. Nevertheless, some of them are morphed as oral avicularia, revealing their kenozooidal origins. Specimens figured by Hayward & Ryland (1998, p. 317, fig. 111) show a slightly different avicularian morphology, being slender and pointed compared to the holotype.

Distribution. Recent, usually found on hard substrata at 60–100 m depth in the fjords of west Norway, in the Barents Sea, on the west coast of Greenland, Faroe Islands, northwest Scotland and Icelandic waters ( Fig. 1 ).

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

Figures

FIGURE 1. Map showing the spatial and temporal distribution of all the studied species. 1, Gephyrotes nitidopunctatus (Smitt, 1868); 2, Gephyrotes fortunensis Pouyet, 2000; 3, Gephyrotes moissettei n. sp.; 4, Gephyrotes spectabilis Canu & Bassler, 1920; 5, Gephyrotes quadriserialis Canu & Bassler, 1920; 6, Gephyrotes convexus Canu & Bassler, 1920; 7, Tricephalopora saillans (Canu & Bassler, 1920); 8, Tricephalopora levigata (Canu & Bassler, 1920); 9, Spiniflabellum spinosum Canu & Bassler, 1928. Open circles, Recent; solid circles, Miocene; diamond, Oligocene; stars, Eocene; triangles, Danian.

FIGURES 2 – 8. Gephyrotes nitidopunctatus (Smitt, 1868), holotype, SMNH 1770, Recent, northern Norway, Finnmark, North Atlantic Ocean: 2, partial view of the colony; small zooids with evident oral spines at lower left probably belong to the periancestrular area; 3, autozooids with completely developed collar-like orificial structures; note the network of tubular kenozooids obscuring zooidal boundaries; 4, a zooid with an ooecium in relation to the distal zooid; 5, autozooids, some exhibiting orificial spines (particularly evident at lower right); 6, zooidal lateral walls with uniporous septula; 7, three zooids showing details of the orificial collar-like structures; 8, a kenozooid with a reduced costate shield between autozooids bounded by further tubular kenozooids. Scale bars: Fig. 2, 1 mm; Figs 3 – 8, 200 Μm.

Tables

TABLE 1. Measurements (in Μm) of Gephyrotes nitidopunctatus (Smitt, 1868), holotype, SMNH 1770.

	N (colonies, zooids)	Mean	SD	Range
Zooid length	1, 10	532	47	430–581
Zooid width	1, 10	319	19	300–346
Avicularia length	1, 10	124	12	96–137
Avicularia width	1, 10	94	7	82–106