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712


Journal of Paleontology 89(5):695–729


Song, 1984, p. 183, figs. 3.1–3.3, 3.8, 3.9; Sergeev, 1989, pl. 2, figs. 1–3, 5, 6, 8; Sergeev and Ogurtsova, 1989, pl. 1, figs. 1–3, 5–9, 12; Golovenok and Belova, 1989, p. 193, figs. 1d–1f; Sergeev, 1992, p. 89, pl. 24, figs. 5, 6, 11, pl. 25, figs. 1a, 1b, 2, 3, 5, 6a, 6b; Burzin, 1995, p. 10–11, 13, pl. 1, figs. 1–3, 4A, pl. 3, fig. 1; Prasad, Uniyal and Asher, 2005, p. 54, pl. 10, figs. 4, 12, Pl. 11, fig. 9; Prasad, 2007, pl. 1, figs. 3, 6, 15; Sergeev, Sharma and Shukla, 2012, p. 296, pl. 19, figs. 1–6, 14 (for additional synonymy, see Burzin, 1995, Golovenok and Belova, 1989, and Sergeev, Sharma, and Shukla, 2012).


Description.—Empty non-tapering cylindrical tubes, rarely exhibiting cell-defining septa, coiled into regular cylindrical spirals. Tube diameters range from 5 to 10 μm; coiled spirals are 20–35 μm in breadth and up to 155 μm long. Cross-walls, when present, define cellular segments 1.5–2.0 μm in length. Tube lateral- and cross-walls are fine-grained ~0.5 μm thick.


Material examined.—A few hundred well-preserved specimens.


Occurrence.—Widely distributed in Ediacaran (Vendian) and Lower Cambrian microfossil assemblages.


Remarks.—In the Chulacktau cherts, the permineralized spirals are commonly infilled by apatite. Golovenok and Belova (1983) described O. parva from units incorrectly assigned to the underlying Chichkan Formation, an error corrected in sub- sequent publications (Decision of Fifth All-union Colloquium on Precambrian Microfossils of the USSR, 1986; Ogurtsova and Sergeev, 1987; Sergeev and Ogurtsova, 1989; Sergeev, 1989, 1992).


Obruchevella parvissima Song, 1984 Figure 8.3, 8.4, 8.7, 8.8


Obruchevella parvissima Song, 1984, p. 183, figs. 3.14–3.16; Sergeev and Ogurtsova, 1989, pl. 1, fig. 11; Sergeev, 1992, p.


90, pl. 25, fig. 4; Prasad, Uniyal and Asher, 2005, p. 54, pl. 11, fig. 10; Prasad, 2007, pl. 1, fig. 16; Sergeev, Sharma and Shukla, 2012, p. 296, pl. 19, fig. 10.


Description.—Thin-walled empty cylindrical tubes, coiled into loose regular spirals in which the walls of adjacent tubes are not in contact. Tube diameters range from 3 to 5 μm; the outer diameter of the spiral coils ranges from 18 to 30 μm whereas their inner boundary ranges from 12 to 20 μm. Tube walls are medium-grained, opaque, and typically ≤1.0 μm thick.


Material examined.—A few well-preserved specimens.


Occurrence.—Ediacaran (Vendian): Nagod Limestone Forma- tion, India; Lower Cambrian: Yuhucun Formation, China; Chulaktau Formation, South Kazakhstan.


Obruchevella cf. O. meishucunensis Song, 1984 Figure 3.6–3.10


Obruchevella cf. O. meishucunensis Song, 1984. Sergeev and Ogurtsova, 1989, pl. 1, fig. 11; Sergeev, 1992, p. 90, pl. 24, fig. 8; Sergeev, Sharma and Shukla, 2012, pl. 19, fig. 7.


Description.—Thin-walled empty cylindrical tubes, coiled into a loose regular spirals in which the walls of adjacent tubes are not in contact. Tube diameters range from 20 to 22 μm; the outer diameter of the spiral coils is ~120 μm whereas their inner boundary is ~80 μm. Tube walls are medium-grained, translu- cent, ~1.0 μm thick.


Material examined.—Several not very well-preserved trichomes. Butterfield, 1994 (in Butterfield, Knoll and Swett, 1994)


Genus Oscillatoriopsis Schopf, 1968, emend. Mendelson and Schopf, 1982, emend.


Type species.—Oscillatoriopsis obtusa Schopf, 1968.


Oscillatoriopsis cuboides Knoll, Strother and Rossi, 1988 Figure 9.7–9.9


Oscillatoriopsis cuboides Knoll, Strother, and Rossi, 1988,


p. 275, 276, fig. 11c; Sergeev, Sharma, and Shukla, 2012, text- fig. 42D.


Description.—Solitary uniseriate unbranched cellular trichomes lacking encompassing sheaths. Terminal cells were not detected in the specimens studied; medial cells are quadrate, cask-shaped, translucent, 13.0–18.5 wide (n = 6, μ = 15μm, σ = 2.3, RSD = 15%) and 15–23μm long (n = 6, μ = 18.6μm, σ = 2.3, RSD = 12%), and have a width-to-length ratio ranging from 1 to 1.5 occurring in trichomes up to 100μm long. Cross walls are translucent, fine- to medium-grained, 0.5–1.0μmthick.


Material examined.—Two well-preserved solitary trichomes.


Occurrence.—Lower Proterozoic: Duck Creek Formation, Australia; Lower Cambrian: Chulaktau Formation, South Kazakhstan.


Remarks.—Oscillatoriopsis cuboides is distinguished from other species of Oscillatoriopsis by its characteristic cell dimensions and cask-shaped, cuboidal, medial cells (Knoll et al., 1988; Sergeev et al., 2012). The Chulaktau specimens are broader than trichomes described from the Paleoproterozoic Duck Creek Formation (Knoll et al., 1988), having cellwidths similar to those ofO. longa. In assigning the Chulaktau specimens to O. cuboides, rather than to O. longa, we have followed the taxonomy of Sergeev et al. (2012) rather than that of Butterfield et al. (1994).


emend. Butterfield, 1994 Oscillatoriopsis longa Timofeev and Hermann, 1979,


(in Butterfield, Knoll and Swett, 1994) Figures 10.5, 10.6, 11.7, 11.8


Oscillatoriopsis longum Timofeev and Hermann, 1979, p. 139, pl. 29, figs. 3, 4.


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