Hemicosciniopsis 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 : 789-791

Genus Hemicosciniopsis Vigneaux, 1949

TYPE SPECIES. — Hemicosciniopsis incrustans Vigneaux, 1949 by original designation.

EMENDED DIAGNOSIS. — Colony encrusting with zooids irregularly arranged. Frontal shield evenly pseudoporous. Orifice dimorphic: cleithridiate in non-ovicellate autozooids, bell-shaped with a broader sinus in ovicellate zooids. Oral spines absent. Avicularia suboral with complete crossbar. Ovicells bulbous with pseudopores and calcification resembling the frontal shield.

REMARKS

Vigneaux (1949) introduced the genus Hemicosciniopsis for Cosciniopsis -like species with differently shaped orifice in nonovicellate and ovicellate(maternal)autozooids.Based onTilbrook’s (2006: 236) revised diagnosis of Cosciniopsis , Hemicosciniopsis differs also in having avicularia. However, although the type species of Cosciniopsis , C. coelatus Canu & Bassler, 1927 , lacks avicularia, other species assigned to the genus, such as the wellknown C. lonchaea ( Busk, 1884) , have latero-oral avicularia.

Hemicosciniopsis incrustans Vigneaux, 1949 ( Fig. 6 )

MATERIAL EXAMINED. — Figured syntype ( Vigneaux 1949: 76, pl. 7, fig. 6), C.B.97-1. This specimen is here designated as the lectotype of the species.

TYPE LOCALITY. — Pessac, Lorient, Gironde, Aquitaine, France.

AGE. — Aquitanian, early Miocene.

DESCRIPTION

Colony encrusting, uniserial, multilaminar ( Fig. 6A ). Zooids irregularly arranged, separated by more or less marked furrows, irregularly polygonal, longer than wide (mean L/W = 1.25). Frontal shield convex,nodular and evenly pseudoporous( Fig.6B, C ); pseudopores circular, large, 15-25 µm in diameter, arranged quincuncially, on average 30 per zooid. Orifice dimorphic: cleithridiate in non-ovicellate autozooids with two small,rounded condyles medially directed, separating an arched anter from a smaller bowl-shaped sinus, about 150 µm long by 130 µm wide ( Fig. 6D ); bell-shaped and slightly larger in ovicellate zooids, about 180 µm long by 150 µm wide, with two robust condyles downwards directed separating an arched anter from a larger, shallow poster ( Fig. 6E ). Depending on the degree of calcification, in some zooids the orifice may be completely or partially obliterated ( Fig. 6B, F ). Sometimes a smooth, imperforate, peristomial ridge surrounds the orifice proximally, enclosing a small, elliptical, adventitious avicularium, proximolaterally directed and with complete crossbar ( Fig. 6F ). Ovicells bulbous resting on the frontal shield of the next distal zooid, calcification pseudoporous and resembling a frontal shield ( Fig. 6B, C, E ).

MEASUREMENTS

ZL 512 ± 46, 457-593 (12); ZW 408 ± 37, 330-451 (12); OvL 208 ± 6, 200-215 (5); OvW 279 ± 18, 265-303 (5); AvL 65 ± 9, 53-74 (5); AvW 43 ± 5, 34-47 (5).

REMARKS

The two small fragments of Hemicosciniopsis incrustans available for study are likely to have encrusted an ephemeral substrate, such as an alga or seagrass, based on the hollow,cylindrical colony-form.

Figures

FIG. 6. — Hemicosciniopsis incrustans Vigneaux,1949,figured syntype C.B.97-1, Aquitanian,early Miocene,Pessac,Lorient,Gironde,Aquitaine,France.A, general view of the colony; B, group of ovicellate and non-ovicellate zooids; C, close-up of an autozooid and ovicellate zooid showing dimorphic orifices; D, close-up of an autozooid orifice with suboral avicularium; E, close-up of the ovicell and orifice of a maternal zooid; F, close-up of a suboral avicularium showing complete crossbar. Scale bars: A, 500 μm; B, C, 200 μm; D, F, 50 μm; E, 100 μm.