Platelinella solea, Taylor & Villier, 2022

Taylor, Paul D. & Villier, Loïc, 2022, Cretaceous microporid cheilostome bryozoans from the Campanian historical stratotype of southwest France, Geodiversitas 44 (18), pp. 515-525 : 519-521

Platelinella solea n. sp.

( Fig. 2 )

urn:lsid:zoobank.org:act:C7F91F73-DC14-4EBE-8C5D-63868421C8FD

ETYMOLOGY. — “ solea ”, meaning horseshoe in Latin, refers to the opesiules arranged in a horseshoe shaped row.

TYPE MATERIAL. — Holotype. NHMUK PI BZ 8564 , Biron Fm, Le Caillaud (north side of cliff), Talmont, Charente-Maritime ( France). — Paratype. NHMUK PI BZ 8848 , Biron Fm , top benthic foram zone CIVb, Le Caillaud (south side of cliff), Talmont, Charente-Maritime ( France).

TYPE LOCALITY. — Biron Fm, Le Caillaud (north side of cliff), Talmont, Charente-Maritime ( France).

OCCURRENCE. — Upper Campanian, Biron Formation.

DESCRIPTION

Colony encrusting, multiserial, sheet-like, unilamellar. Autozooids slightly longer than wide, ZL 435-611 µm (N colonies 2; N zooids 10; mean 484 µm; SD 58 µm), ZW 353-412 µm (N colonies 2; N zooids 10; mean 388 µm; SD 20 µm), wellrounded distally. Frontal wall with cryptocyst finely granular, forming most of the frontal surface, a narrow raised, convex gymnocystal rim surrounding an extensive flat to slightly concave central cryptocystal region; occasional cryptocystal pores; 8-10 opesiules distributed evenly in a horseshoe shaped row at the outer edge of the central part of the cryptocyst, decreasing in size proximally, not clearly paired, oval, elongated radially, countersunk. Orifice semielliptical, wider than long, OL 106- 118 μm (N colonies 2; N zooids 10; mean 109 μm; SD 10 μm), OW 118- 153μm (N colonies 2; N zooids 10; mean 136 μm; SD 11 μm), the proximal edge gently convex, a narrow opercular shelf around the distal edge. Ovicells not observed; occasional zooids with slightly larger orifices (OL 115 μm, OW 170 μm) may perhaps have been brooding zooids. Avicularia absent. Ancestrula and early astogenetic stages not observed. Pore chambers lacking; a pair of septular pores visible in the distal vertical walls and a pair in the distolateral vertical walls.

REMARKS

Compared with the type and only previously described species of the most similar genus, Metamicropora , P. solea has radially rather than longitudinally elongate opesiules, which number 10-12 (12-18 in M. areolae ), autozooids bordered by a narrow gymnocyst rather than the granular raised edge of the cryptocyst, and an opercular shelf along the distal edge of the orifice. It is readily distinguished from other microporid species recorded in the Campanian of SW France by the large number of opesiules which are distributed all around the lateral and proximal margins of the cryptocyst.

Figures

FIG. 2. — Platelinella solea n. gen.et n. sp.: A-E, holotype,NHMUK PI BZ 8564, Biron Fm, Caillaud (north side),Talmont,Charente-Maritime:A, part of the colony; B, group of zooids; C, zooid with narrow distal opercular shelf; D, group of zooids, one with a slightly enlarged orifice (upper centre); E, broken zooid revealing two distal and two distolateral septular pores; F, paratype, NHMUK PI BZ 8848, Biron Fm, Caillaud (south side), Talmont, Charente-Maritime, group of zooids. Scale bars: A, 1 mm; B, D, F, 500 μm; C, E 100 μm.