Rectifenestella submicroporata (Schulga-Nesterenko, 1952)

Nakrem, Hans Arne, Błażejowski, Błażej & Gaździcki, Andrzej, 2009, Lower Permian bryozoans from southern and central Spitsbergen, Svalbard, Acta Palaeontologica Polonica 54 (4), pp. 677-698 : 694-695

Rectifenestella submicroporata

(Shul’ga−Nesterenko, 1952)

Fig. 8N.

Material examined.—Treskelen, sample and one thin section ZPAL Br. 12/Cr. 34; Gipsvika, thin sections PMO 170.915A and B, 170.938B. See also occurrences listed in Nakrem (1994a: 93).

Description.—Delicate meshwork with 21–28 fenestrules along colony and 25–29 branches across colony per 10 mm. Branches about 0.21 mm thick and 0.23 mm wide with a straight low carina carrying 5–6 nodes per 1 mm. Nodes are about 0.05 mm long and 0.03 mm wide being 0.16–0.21 mm apart. Dissepiments 0.07–0.12 mm wide. Fenestrules 0.26–0.34 mm long and 0.12–0.20 mm wide. Apertures circular in outline, 0.06–0.09 mm in diameter. There are usually 25–27 apertures per 5 mm along branch. Distance between apertural centers along colony 0.17–0.22 mm; 2 or 2.5 apertures border each fenestrule. Zooecial chambers are pentagonal in outline in median tangential section.

Remarks.— R. submicroporata is distinguished from R. microporata by smaller apertures (0.06–0.09 vs. 0.07 mm in diameter) and narrower and more closely spaced branches and dissepiments. A fragmentary specimen assigned as Rectifenestella cf. submicroporata (Shul’ga−Nesterenko 1952) (one ZPAL thin section from Hyrnefjellet) is separated by having more robust branches and dissepiments and the following measurements: 23–25 branches per 10 mm, width of branch 0.28–0.30 mm, width of dissepiments 0.25–0.26 mm.

Measurements.—See Table 10.

Stratigraphic and geographic range.—Occurrence on Svalbard: Late Asselian–early Sakmarian, middle and upper part of the Tyrrellfjellet Member, and late Artinskian−early Kungurian, Vøringen Member of the Kapp Starostin Formation. Asselian of the Urals, Russia (Shul’ga−Nesterenko 1952).