Spinofenestella sp.

Ernst, Andrej, 2016, Bryozoan fauna from the Permian (Artinskian-Kungurian) Zhongba Formation of southwestern Tibet, Palaeontologia Electronica (1946) 51 (9), pp. 1-59 : 37

Spinofenestella sp.

Figure 17.1-5 ; Table 22

Material. SMF 23.178.

Exterior description. Reticulate colony formed by straight branches joined by wide dissepiments. Fenestrules oval to rectangular, short, narrow. Autozooecia arranged in two rows on branches.

Autozooecial apertures circular, with stellate structure; two apertures spaced per fenestrule length. Median keel low, narrow, containing small closely spaced rounded nodes. Large nodes on the reverse side of branches.

Interior description. Autozooecia short, triangular to trapezoid in mid-tangential section; with short to moderately long vestibule in longitudinal section. Axial wall between autozooecial rows strongly zigzag; aperture positioned at distal end of chamber. Superior hemisepta weakly developed; inferior hemisepta absent. External laminated skeleton well-developed on both obverse and reverse sides, traversed by small microstyles. Heteromorphs not observed.

Remarks. Spinofenestella sp. is similar to S. cibaria ( Trizna, 1950) from the Lower Permian of Russia, but differs from it in presence of nodes on the reverse colony side and wider branches (0.28– 0.34 mm vs. 0.20–0.30 mm in S. cibaria ). Spinofenestella sp. differs from S. microaperturata ( Schulga-Nesterenko, 1941) from the Lower Permian of Russia in the presence of nodes on the reverse colony side and wider branches (0.38– 0.34 mm vs. 0.20–0.30 mm in S. microaperturata ).

Minilya magnispinata ( Schulga-Nesterenko, 1952) , from the Lower Permian of Urals, has similar colony dimensions and similar kinds of nodes on the reverse colony side. However, the latter species has alternating nodes on the keel (characteristic of the genus Minilya ) and narrower branches (branch width 0.22–0.25 mm vs. 0.28– 0.34 mm in the present species).

Occurrence. Zhongba Formation, Permian (upper Cisuralian –Guadalupian); Zhongba area of southwestern Tibet .

Figures

FIGURE 17. Thin section photographs of Spinofenestella sp., SMF 23.178 (1–5); and Spinofenestella subquadratopora (Schulga-Nesterenko, 1952), SMF 23. 179 (6–8). 1–3, tangential section of the reverse side; 4–7, tangential section of the obverse side; and 8, mid- tangential section.