Liguloclema meridianus (Etheridge, 1926)

Ernst, Andrej, 2016, Bryozoan fauna from the Permian (Artinskian-Kungurian) Zhongba Formation of southwestern Tibet, Palaeontologia Electronica (1946) 51 (9), pp. 1-59 : 18-20

Liguloclema meridianus (Etheridge, 1926)

Figures 8.8 , 9.1-5 ; Table 10

1926 Sulcoretepora (?) meridianus Etheridge , in Bretnall, p. 19, pl. 1, fig. 9.

1931 Sulcoretepora (?) meridianus Etheridge, 1926 ; Hosking, p. 15.

1944 " Sulcoretepora " meridianus Etheridge, 1926 ; Crockford, p. 156, pl. 4, fig. 6, text-figs. 29- 30.

1957 Liguloclema meridianus (Etheridge, 1926) ; Crockford, p. 37.

1988 Liguloclema meridianus (Etheridge, 1926) ; Yanagida, J. a Research Group, p. 17, figs. 2-3.

1987 Liguloclema cf. meridianus (Etheridge, 1926) ; Liu and Wang, p. 7, figs. 7-8.

1993 Liguloclema meridianus (Etheridge, 1926) ; Engel and Ross, p. 17, pl. 13, figs. 1-3.

1973 Liguloclema cf. meridianus (Etheridge, 1926) ; Sakagami, p. 77-78, pl. 11, figs. 1-4.

1999 Liguloclema meridianus (Etheridge, 1926) ; Sakagami, p. 86-87, pl. 21, figs. 1-3.

Material. SMF 23.081– SMF 23.098.

Description. Colony narrow bifoliate branches, dichotoming in plane of mesotheca. Branches 1.4– 3.4 mm wide and 1.1–1.9 mm thick, lens-shaped in transverse section. Branch edges rounded, lacking autozooecia. Autozooecia tubular, rhombically arranged in 8–13 longitudinal rows on branches, lacking on lateral sides of branches; subquadrate, trapezoid to subhemispherical in transverse section at mesotheca; angular shaped in deep tangential section in mid exozone and partially isolated by vesicles. Long and thin hook-shaped superior hemisepta present at the transition between endo- and exozone, curved proximally, club-shaped. Basal diaphragms rare. Mesotheca consisting of granular–prismatic material, straight, 0.03–0.04 mm thick; median tubules present, 0.010 –0.015 mm in diameter; longitudinal ridges absent. Autozooecial walls granular–prismatic, 0.013 –0.015 mm thick. Autozooecial apertures arranged regularly in 9–13 diagonal rows on branches, rounded to oval. Lunaria absent. Vesicular skeleton well-developed, restricted to exozone; vesicles blister-like, low to moderately high with flat to rounded roofs, polygonal (mainly rectangular) in tangential section. Extrazooecial skeleton well-developed, displaying cloudy structure. Acanthostyles absent. Monticules absent.

Remarks. Two species are placed in the genus Liguloclema , L. typicalis Crockford, 1957 and L. meridianus (Etheridge, 1926) , both originally known from the Noonkanbah Formation, Lower Permian (Artinskian–Kungurian) of Western Australia. Crockford (1957, p. 37) provided neither detailed description of L. meridianus nor made a comprehensive comparison between L. typicalis and L. meridianus . The only difference she mentioned was the smaller branch width of L. meridianus against L. typicalis (less than 1.8 mm vs. 3.3– 5.0 mm in L. typicalis ). The present material of Liguloclema meridianus differs from L. typicalis in larger distances between aperture centres (0.52– 0.95 mm vs. 0.43–0.55 mm in L. typicalis ).

Occurrence. Noonkanbah Formation, Lower Permian (upper Artinskian-Kungurian); Western Australia. Rat Buri Limestone, Lower Permian (?Artinskian–Kungurian); Khao Raen, Thailand. Permian,?Wordian; Khao Hin Kling area, north-central Thailand. Xiala Formation,?Middle Permian; Xainza, southwestern Tibet. Zhongba Formation, Permian (upper Cisuralian–Guadalupian); Zhongba area of southwestern Tibet.

Figures

FIGURE 8. Thin section photographs of Goniocladia aff. indica Waagen and Pichl, 1885, SMF 23.076 (1 and 2), SMF 23.077 (3–5), and SMF 23.073 (6 and 7); and Liguloclema meridianus (Etheridge, 1926), SMF 23.093 (8). 1–2, and 6, branch transverse sections showing autozooecia chambers, mesotheca and hemisepta (arrow); 3–5, tangential sections showing autozooecial apertures; 7, longitudinal section showing autozooecial chamber with superior hemisepta (arrow); and 8, branch oblique section showing mesotheca, autozooecial chambers with hemisepta and vesicular skeleton.

FIGURE 9. Thin section photographs of Liguloclema meridianus (Etheridge, 1926), SMF 23.093 (1), SMF 23.085 (2), and SMF 23.083 (3–5); and Etherella tibetensis n. sp., paratype SMF 23.217 (6). 1 and 2, branch oblique section showing mesotheca, autozooecial chambers with hemisepta and vesicular skeleton; 3 and 4, mid-tangential section showing autozooecial chambers with hemisepta; 5, tangential section showing autozooecial apertures; and 6, transverse section showing extrazooecial skeleton and sparse vesicles.