716
Journal of Paleontology 89(5):695–729
Oscillatoriopsis longa Butterfield, Knoll and Swett, 1994, p. 60, figs. 24F–24G; Dong, Xiao, Shen, Zhou, Li and Yao, 2009,
p. 39, figs. 6.10–6.11 (For additional synonymy see Butterfield et al., 1994 and Zhang et al., 1998).
Description.—Uniseriate straight to curved unbranched non- ensheathed trichomes that lack cell-defining constrictions and occur commonly as isolated individuals. Terminal cells are rounded to hemispheroidal, 12–21 μmwide (n = 5) and 4–6 μm long (n = 5); medial cells are disc-shaped, translucent, 23– 30 μmwide(n = 48, μ = 26 μm, σ = 1.6, RSD = 6%), 4–9 μm long (n = 48, μ = 6 μm, σ = 1.0, RSD = 16%), and have a width to length ratio 4 to 8; trichome lengths range from 180 to 270 μm. Transverse cell walls are commonly indistinct whereas the trichome-defining lateral cell walls are typically distinct, translucent to opaque, fine- to medium grained, and 0.5–1.0 μm thick. Preserved remnants of degraded cytoplasm, a few micrometers wide and up to a few tens of micrometers long, occur commonly as thread-like inclusions inside the trichomes.
Material examined.—A few dozen well-preserved trichomes.
Occurrence.—Widely distributed in Proterozoic and Lower Cambrian microfossil assemblages.
Remarks.—Oscillatoriopsis longa is distinguished from other species of Oscillatoriopsis by its characteristic cell dimensions and its trichomic breadth. Although the diameter of trichomes of O. longa from the Chulaktau Formation is up to 35 μm— appreciably broader than the 25 μm upper size limit recognized by Butterfield et al. (1994) and Sergeev et al. (2012) for this taxon —similarly sized specimens of O. longa have been described from the Chulaktau-contemporaneous Yanjiahe and Yurtus formations of China (Dong et al., 2009). Only one other broader taxon of the genus has been reported, O. majuscula, described from a single incomplete specimen 63 μm in diameter from the Paleoproterozoic Duck Creek Formation (Knoll et al., 1988) and a species, however, that was not included in the Butterfield et al. (1994) taxonomic monograph of the genus.
Butterfield, 1994 (in Butterfield, Knoll and Swett, 1994) Genus Palaeolyngbya Schopf, 1968, emend.
Type species.—Palaeolyngbya barghoorniana Schopf, 1968. Palaeolyngbya catenata Hermann, 1974
Figures 9.10, 9.11, 10.1–10.4, 10.9, 10.10, 11.1–11.6
Palaeolyngbya catenata Hermann, 1974, p. 8 and 9, pl. 6, fig. 5; Butterfield, Knoll and Swett, 1994, p. 61, figs. 25F–25G; Sergeev and Lee Seong-Joo, 2001, p. 6, pl. 1, figs. 4–6; Sergeev and Lee Seong-Joo, 2004, p. 13, 15, pl. 2, figs. 1–3; Srivastava and Kumar, 2003, p. 30, 32, pl. 9, figs. 5, 7; Sergeev, 2006, p. 207, pl. 22, figs. 4–6, pl. 27, figs. 1–3; Sergeev, Sharma and Shukla, 2008, pl. 4, fig. 5, pl. 7, fig. 12, pl. 9, fig. 4; 2012, p. 300, 301, pl. 18, figs. 1–5, 8, text-fig. 43B.
Palaeolyngbya maxima Zhang, 1981, p. 495, pl. 2, figs.4,6,7(for additional synonymy, see Sergeev, Sharma, and Shukla, 2012).
Description.—Unbranched uniseriate trichomes having discoidal medial cells and rounded terminal cells that lack constrictions at septa and are encompassed by a prominent non- lamellated smooth sheath. Terminal cells are rounded to hemi- spheroidal, 22–26 μmwide and up to 7 μmlong; medial cells are 28–35 μm wide (n = 60, μ = 32.5 μm, σ = 1.7, RSD = 5%) and 7–11 μm long (n = 60, μ = 8.5 μm, σ = 1.6, RSD = 18.5%), having a width-to-length ratio ranging from 3 to 5. Transverse cell walls are commonly indistinct; lateral, trichome- defining walls are translucent, fine-grained and 0.5–1.0 μm thick. Encompassing extracellular sheaths are translucent, 29–39 μm in diameter, 0.5–1.5 μm thick and up to 900 μm long.
Material examined.—More than one hundred well-preserved filaments.
Occurrence.—Widely distributed in Proterozoic microfossil assemblages.
Remarks.—The diameter of trichomes of P. catenata in the Chulaktau assemblage ranges up to 35 μm, broader than the
upper size limit previously recognized for this species (Butter- field et al., 1994; Sergeev et al., 2012). In sheath diameter, the Chulaktau specimens span the range between P. castenata and P. hebeiensis (Zhang and Yan, 1984).
Palaeolyngbya sp. Figure 11.12, 11.13
Description.—Unbranched uniseriate trichomes, up to 53 μm long, exhibiting discoidal medial cells and rounded terminal cells that lack constrictions at septa and are surrounded by a prominent unilayered smooth sheath. Medial cells are 6–7 μm wide and 1–2 μm long. Transverse walls are indistinct or miss- ing; lateral cell walls are translucent, fine-grained, 0.5–1.0 μm thick. The encompassing sheath is translucent, single-layered, ~9 μm broad and ~0.5 μm thick.
Material examined.—One filament, not well preserved.
Genus Siphonophycus Schopf, 1968, emend. Knoll and Golubic, 1979, emend. Knoll, Swett and Mark, 1991
Type species.—Siphonophycus kestron Schopf, 1968. Siphonophycus robustum (Schopf, 1968), emend.
Knoll and Golubic, 1979, comb. Knoll, Swett, and Mark, 1991 Figure 11.11
Eomycetopsis robusta Schopf, 1968, p. 685, рl. 82, figs. 2, 3; рl. 83, figs. 1–4; Knoll and Golubic, 1979, p. 149, figs. 4A, 4B; Mendelson and Schopf, 1982, p. 59, 60, 62, pl. 1, figs. 9, 10; Ogurtsova, 1985, p. 97 and 98, pl. 3, figs. 4, 6, pl. 10, figs. 1–6, pl. 11, figs. 2, 3, 5, 6; pl. 12, figs. 1, 3, 5, 7; Sergeev, 1992,
p. 93 and 94, pl. 7, figs. 9, 10; pl. 16, figs. 3, 6, 7, 10; pl. 19, figs. 1, 5, 6, 7–10; pl. 24, fig. 7; Golovenok and Belova, 1993, pl. 2, fig. е.
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