Stephanollina Vigneaux, 1949

Martino, Emanuela Di & Taylor, Paul D., 2017, Some Miocene cheilostome bryozoan genera of Michel Vigneaux - systematic revision and scanning electron microscopic study, Geodiversitas 39 (4), pp. 783-796 : 787-788

Genus Stephanollina Vigneaux, 1949

TYPE SPECIES. — Stephanollona (Stephanollina) dentata Vigneaux, 1949 by original designation.

EMENDED DIAGNOSIS. — Colony encrusting. Zooids with ill-defined boundaries. Frontal shield nodular, imperforate apart from sparse marginal areolar pores. Primary orifice with a shallow sinus; secondary orifice cormidial with lobes and cusps. Oral spines present. Avicularia adventitious, budded from marginal areolar pores. Ovicell globular.

REMARKS

Stephanollina was introduced by Vigneaux (1949) as a subgenus of Stephanollona Duvergier. Gordon (2006) ruled out any relationship between Stephanollina and Stephanollona , suggesting elevation of Stephanollina to genus rank and tentatively including it in the family Sfeniellidae . However, the diagnosis of the family Sfeniellidae is based solely on Sfeniella and must be modified to include Stephanollina (see above). The latter genus lacks the sparse pseudopores penetrating the frontal shield and the polymorphs resembling autozooids but with reduced orifices that are typical of Sfeniella , while avicularia are present. Stephanollina shares with Sfeniella a cormidial secondary orifice and the presence of oral spine bases. The diagnostic features of Stephanollina were observed also in ‘ Gemelliporella ’ vorax Canu & Bassler, 1923 sensu Gordon (2006 : pl. 2, figs 3, 4), which is here considered as congeneric, although limited to the specimens re-examined by Gordon (2006) from the Miocene of North Carolina. Other specimens figured in Canu & Bassler (1923: pl. 19, figs 1-9) seem to belong to different genera.

Stephanollina dentata Vigneaux, 1949 ( Fig. 4 )

MATERIAL EXAMINED. — Figured syntype ( Vigneaux 1949: 80, pl. 7, fig. 13), C.B.429-1. This specimen is here designated as the lectotype of the species.

TYPE LOCALITY. — Manciet, Gers, Aquitaine, France.

AGE. — Langhian, middle Miocene.

DESCRIPTION

Colony encrusting, multiserial, unilaminar ( Fig. 4A ). Zooids quincuncially arranged with ill-defined boundaries, sometimes marked by marginal areolar pores or narrow, shallow furrows ( Fig. 4A, B ). Frontal shield slightly convex or flat, nodular, imperforate apart from sparse, circular to elliptical, marginal areolar pores, 15-30 µm long ( Fig. 4B ). Primary orifice somewhat rounded, almost equidimensional, with two small condyles proximally placed separating an arched anter from a very shallow, slightly narrower sinus with a faintly concave proximal margin ( Fig. 4C, D ). Secondary orifice cormidial, formed by the frontal shield of the three surrounding distal zooids, forming a crenulated margin of lobes and cusps, the latter in the position of the oral spines ( Fig. 4C, D ). A suboral mucro rarely developed ( Fig. 4A , see arrow). Five distal oral spine bases, the proximalmost pair generally larger, about 20 µm in diameter, while the others are about 10 µm in diameter ( Fig.4C, D ). Adventitious avicularia budded from marginal areolar pores, often latero-oral, elliptical, without condyles or pivotal bar ( Fig. 4B, C ). No complete ovicells observed; incomplete ovicells with ooecium longer than broad, resting on the frontal shield of the next distal zooid or pair of zooids ( Fig. 4A, B ).

MEASUREMENTS

ZL 275 ± 20, 247-329 (15); ZW 223 ± 26, 186-276 (15); OL 76 ± 4, 71-82 (10); OW 86 ± 1, 84-88 (10); OvL 103 ± 6, 96-113 (5); OvW 150 ± 14, 127-162 (5); AvL 63 ± 6, 53-71 (10); AvW 49 ± 6, 40-57 (10).

REMARKS

Stephanollina dentata is very similar in appearance to the specimen of Stephanollina vorax ( Canu & Bassler, 1923) n. comb. figured by Gordon (2006: pl. 2, figs 3, 4), the two species differing mainly in the number of oral spine bases (five in S. dentata , four in S. vorax n. comb.), and in the shape of the orificial sinus, which is deeper and more markedly concave in S. vorax n. comb. Ovicells and avicularian chambers are generally broken or incomplete in both species.

Figures

FIG. 4. — Stephanollina dentata Vigneaux, 1949, figured syntype C.B.429-1, Langhian, middle Miocene, Manciet, Gers, Aquitaine, France: A, general view of the colony; the arrow shows an autozooid with developed suboral mucro; B, group of zooids with incomplete ovicells and broken avicularian chambers; C, close-up of two autozooids with elliptical avicularia; D, close-up of the primary orifice showing five oral spine bases and the cormidial secondary orifice with alternating lobes and cusps. Scale bars: A, 200 μm; B, 100 μm; C, D, 50 μm.