Hexagonella kobayashii Sakagami, 1968

Ernst, Andrej, 2016, Bryozoan fauna from the Permian (Artinskian-Kungurian) Zhongba Formation of southwestern Tibet, Palaeontologia Electronica (1946) 51 (9), pp. 1-59 : 14

Hexagonella kobayashii Sakagami, 1968

Figures 6.8-11, 7.1-4 ; Table 8

1968 Hexagonella kobayashii Sakagami , p. 50-51, pl. 9, figs. 3-5; 1976, pl. 25, figs. 7-9.

1976 Hexagonella kobayashii Sakagami, 1968 ; Sakagami, pl. 25, figs. 7-9.

1997 Hexagonella kobayashii Sakagami, 1968 ; Sakagami and Pillevuit, p. 206, figs. 2.4-5, 3.1-3.

2008 Hexagonella kobayashii Sakagami, 1968 ; Ernst, Weidlich and Schäfer, p. 680-682, figs. 3.5, 3.7, 3.8, 4.1.

Material. Six thin sections of single colony SMF

23.067– SMF 23.072.

Description. Free-branched bifoliate colony.

Branches elliptical in transverse section, 6.9–8.6

mm wide and 3.0– 4.5 mm thick. Mesotheca straight, three-layered, 0.05–0.10 mm thick, containing median tubules. Autozooecia long, tubular,

bending gently in exozone. Apertures rounded to oval. Lunaria distinct. Diaphragms rare, 1–2 in each autozooecium, thin, planar. Vesicles large, box–like with rounded roofs, separating autozooecia in 2–3 rows, 8–10 surrounding each autozooecia aperture. Autozooecial walls granular, 0.008 – 0.018 mm thick. Thick layer of granular skeleton in the outermost exozone. Crests on the colony surface building regular hexagonal patterns. Maculae not observed.

Remarks. Hexagonella kobayashii Sakagami, 1968 is similar to H. turgida Bassler, 1929 from Permian of Timor. The latter species differs in having smaller autozooecial apertures (ca. 0.20 mm vs. 0.19–0.25 mm in H. kobayashii ).

Occurrence. Rat Buri Limestone (Khao Phrick), Lower Permian (Artinskian); Thailand. Aseelah Unit, Saal Formation, Lower–?Middle Permian; Batain Coast (eastern Oman). Zhongba Formation, Permian (upper Cisuralian–Guadalupian); Zhongba area of southwestern Tibet.

Figures

FIGURE 6. Thin section photographs of Eridopora uncata Yang and Lu, 1983, SMF 23.052 (1–3); Cyclotrypa alexanderi Sakagami, 1963 SMF 23.056 (4–5), SMF 23.061 (6), and SMF 23.056 (7); and Hexagonella kobayashii Sakagami, 1968, SMF 23.069 (8–9) and SMF 23.070 (10 and 11). 1–3, tangential section showing autozooecial apertures with lunarial ends indenting into the aperture (arrow); 7, tangential section showing autozooecia and macrozooecia (arrow); 8 and 9, branch transverse section showing autozooecial chambers and vesicular skeleton; and 10 and 11, longitudinal section showing autozooecial chambers and vesicular skeleton.

FIGURE 7. Thin section photographs of Hexagonella kobayashii Sakagami, 1968, SMF 23.067 (1–3) and SMF 23.072 (4); and Goniocladia aff. indica Waagen and Pichl, 1885, SMF 23.266 (5), SMF 23.077 (6), and SMF 23.073 (7). 1–3 and 6, tangential section; 7, mid-tangential section showing autozooecial chamber; 4, transverse section showing mesotheca with median tubules (arrow); and 5, external view of the colony form the reverse side.

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.

FIGURE 10. Thin section photographs of Etherella tibetensis n. sp., paratype SMF 23.267 (1), paratype SMF 23.216 (2), paratype SMF 23.219 (3 and 4), holotype SMF 23.214 (5–7), and paratype SMF 23.230 (8 and 9). 1, external view of the colony (split along mesotheca); 2–4, tangential section showing arrangement of autozooecia and wall microstructure; 5–7, oblique section showing hemisepta and mesotheca (arrows); and 8 and 9, branch transverse section showing autozooecial chambers and extrazooecial skeleton.

FIGURE 11. Thin section photographs of Tabulipora xinjiangensis Yang and Lu, 1983, SMF 23.233 (1 and 2); Dyscritella lii n. sp., holotype SMF 23.235 (3, 4, and 6) and paratype SMF 23.236 (5); and Ulrichotrypella omanica Ernst et al., 2008, SMF 23.242 (7 and 8). 1, longitudinal section showing ring septa; 2, oblique section showing macroacanthostyles and tubules; 3 and 4, oblique section through the colony; 5 and 6, tangential section showing autozooecial apertures and acanthostyles; and 7 and 8, oblique section.