Taxonomy and diversity of coelobite bryozoans from drift coral cobbles on Co To Island, northern Vietnam
Author
Dick, Matthew H.
Author
Ngai, Nguyen Danh
Author
Doan, Hung Dinh
text
Zootaxa
2020
2020-03-03
4747
2
201
252
journal article
10.11646/zootaxa.4747.2.1
55ab330e-0468-42ed-aeb0-7850751cf989
1175-5326
3694740
6AA8F5DC-8D70-42B0-B016-6F9C4211C471
Plesiocleidochasma porcellaniforme
(
Soule, Soule & Chaney, 1991b
)
(
Figs 14
,
20G
)
Schedocleidochasma porcellaniforme
Soule, Soule & Chaney, 1991b
, p. 481
, pl. 1, fig. 1, pl. 5, figs 3, 4, and synonyms therein.
Schedocleidochasma porcellaniforme
:
Tilbrook
et al
. 2001
, p. 98
, fig. 21A, B;
Liu
et al
. 2001
, 705, pl. 79, figs 1–3;
Tilbrook 2006
, p. 293, pl. 64B.
Cleidochasma porcellanum
(Busk)
:
Winston and Heimberg 1986
, p. 34, figs 85–87.
Material examined.
VNMN-0256 (CT-7), VNMN-0257 (CT-8), VNMN-0258 (CT-13), VNMN-0259 (CT-15), VNMN-0260 (CT-29), VNMN-0261 (CT-31), on SEM stubs.
Measurements. AzL
, 0.37–0.47 (0.403 ± 0.025);
AzW
, 0.22–0.39 (0.306 ± 0.041) (n = 15, 1).
OrL
, 0.11–0.15 (0.131 ± 0.010);
OrW
,
0.089
–0.115
(0.099 ± 0.007) (n = 15, 2).
OvL
, 0.17–0.22 (0.194 ± 0.015);
OvW
, 0.19–0.25 (0.221 ± 0.015) (n = 15, 1).
Description.
Colony unilaminar, encrusting, sheet-like; sometimes partly bilaminar due to self-overgrowth.
Zooids small, boundaries indistinct. Frontal wall slightly convex, imperforate; surface weakly pustulose; often bearing several scattered, low, rounded nodules; with a few marginal pores, some of which may be positioned inside margin. Marginal zooids show three small spine bases, which are not evident in interior zooids. Orifice keyhole-shaped; anter circular or subcircular, separated by strong, proximomedially directed condyles from narrower, rounded poster.
Frontal avicularia single or paired lateral or proximolateral to poster, although zooids lacking frontal avicularia not uncommon. When paired, avicularia directed at slightly different angles, one sometimes pointing laterally and other distolaterally. Avicularian rostrum rounded proximally, acute distally; crossbar complete or incomplete; opesial opening more or less arrowhead-shaped.
Ooecium subimmersed, imperforate, same texture as frontal wall; opening covered by broad, flat labellum, with narrow transverse slit above, distinct lateral slits, and narrow transverse slit below that merges with lateral slits.
Remarks.
This species was originally placed in the genus
Schedocleidochasma
Soule, Soule & Chaney, 1991b
, but
Berning (2012)
, concluding that no clear boundary could be drawn between that genus and
Plesiocleidochasma
, declared the former a junior synonym of the latter.
Distribution.
Widely distributed in the central to western Pacific, ranging from the Hawaiian Islands westward to
Indonesia
,
Thailand
,
Vietnam
, and the
Maldives
(Indian Ocean) (
Soule
et al
. 1991b
;
Tilbrook 2006
; this study).