Hemiphylactella 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 : 784-785

Genus Hemiphylactella Vigneaux, 1949

TYPE SPECIES. — Hemiphylactella pulchra Vigneaux, 1949 by original designation.

EMENDED DIAGNOSIS. — Colony encrusting, multiserial, unilaminar, with zooids arranged quincuncially.Zooids with convex frontal shield, tubercular or smooth, imperforate apart from a single row of marginal areolar pores. Primary orifice with a straight, convex or concave proximal margin and small condyles, surrounded by a flared to tubular peristome; oral spines present or absent. Ovicells hyperstomial, small, globular. Avicularia absent. Pore-chamber windows present or absent.

REMARKS

In addition to the Burdigalian type species, Hemiphylactella pulchra ( Fig. 1 ; see description below), two Serravallian species were included by Vigneaux (1949) in this genus: H.? crassovicellata ( Fig. 2 ; see description below) and H.? latebrosa ( Fig. 3 ; see description below), both from Salles, Gironde.

Hemiphylactella is similar to the smittinid Phylactella Hincks, 1879 in having a deep flaring peristome, but differs in having oral spines, an imperforate frontal shield and ovicell, and in lacking a lyrula. Among other genera included in Romancheinidae , Escharella Gray, 1848 is the most similar, differing from Hemiphylactella most conspicuously in having a large lyrula.

Hemiphylactella pulchra Vigneaux, 1949 ( Fig. 1 )

MATERIAL EXAMINED. — Figured syntype ( Vigneaux 1949: 84, pl. 8, fig. 1), C.B.398. This specimen is here designated as the lectotype of the species.

TYPE LOCALITY. — Moulindel’Eglise,Saucats,Gironde, Aquitaine, France.

AGE. — Burdigalian, early Miocene. DESCRIPTION

Colony encrusting, multiserial, unilaminar ( Fig. 1A ). Ancestrula unknown; astogenetically oldest preserved zooid, probably the first budded autozooid ( Fig. 1B , see arrow), similar to later autozooids but smaller, about 245 µm long by 180 µm wide, and bearing four oral spine bases. Zooids arranged quincuncially, distinct, boundaries marked by very narrow furrows, hexagonal, longer than wide (mean L/W = 1.24). Frontal shield slightly convex, tubercular, imperforate except for a single row of marginal areolar pores, on average 18 per zooid, oval to circular, 15-25 µm in diameter ( Fig. 1C ). Orifice placed distally, broader than long, the proximal rim slightly convex or straight and with two tiny condyles placed proximally to the mid-lateral position ( Fig. 1D ). A smooth, flared peristome, more developed proximally and laterally than distally, surrounds the orifice, embedding generally two, rarely three ( Fig. 1C ), distal, largely spaced oral spine bases, 25-35 µm in diameter. Ovicells hyperstomial. Ooecium small, about 95 µm long by 165 µm wide, globular, cap-like, with a finer granulation than the frontal shield ( Fig. 1E ); the proximal rim of the ooecium is covered by the smooth upturned peristome. At least one oral spine base is still visible in ovicellate zooids ( Fig. 1E ). Avicularia absent. Numerous, oval pore-chamber windows visible at colony growing edge along the distolateral zooidal margin, 25-40 µm long by 10- 15 µm wide ( Fig. 1C ).

MEASUREMENTS

ZL 416 ± 25, 365-470 (20); ZW 337 ± 26, 277-389 (20); OL 64 ± 6, 48-75 (20); OW 94 ± 4, 87-103 (20).

REMARKS

Several differences occur between Hemiphylactella pulchra and the two congeneric species, such as the presence/absence of oral spine bases and pore-chamber windows (see below).

Figures

FIG. 1. — Hemiphylactella pulchra Vigneaux, 1949, figured syntype C.B.398, Burdigalian, early Miocene, Moulin de l’Église, Saucats, Gironde, Aquitaine, France: A, general view of the colony; B,?first budded zooid (see arrow) and early astogeny; C, group of autozooids with a single ovicellate zooid; D, close-up of an autozooid; E, close-up of the ooecium. Scale bars: A, 500 μm; B, 100 μm; C, 200 μm; D, E, 50 μm.

FIG. 2. — Hemiphylactella? crassovicellata Vigneaux,1949, figured syntype C.B.450, Serravallian, middle Miocene, Salles, Gironde,Aquitaine,France: A, general view of the colony; B,?ancestrula and early astogeny; C, close-up of an ovicellate zooid and autozooid showing the cleithridiate orifice. Scale bars: A, 500 μm; B, 200 μm; C, 100 μm.

FIG. 3. — Hemiphylactella? latebrosa Vigneaux, 1949, figured syntype C.B.451, Serravallian, middle Miocene, Salles, Gironde, Aquitaine, France: A, general view of the colony with?ancestrula (see arrow) and early astogeny;B, close-up of an ovicellate zooid and autozooid; note the smooth frontal shield and frontal surface of the ooecium where not affected by recrystallization. Marginal areolar pores are visible in the bottom left corner; C, close-up of the ooecium and?cleithridiate orifice. Scale bars: A, 500 μm; B, 100 μm; C, 50 μm.