Type species.—Blastanosphaira kokkoda, by monotypy

Diagnosis.—As for type species.

Etymology.—From the greek βλασταυω, to bud or to germinate, σϕαιρα, sphere, and κκκωδη, granular.

Holotype.—Specimen Figure 2.1, palynological slide U5 569.1 m, England finder coordinates R/S42, from the Wood Duck Member of the Mainoru Formation, Roper Group.

Diagnosis.—Spheromorph, a few up to ~100 µm in diameter, with very thin chagrinate wall, small sinuous folds, and one lanceolate fold predominantly near the margins of compressed vesicles. Division by budding, with one or several large spherical scars left by detaching buds; serial budding without cells detaching common, leading to a colonial habit. Commonly, taphonomic alteration results in the thin wall peeling off the vesicle from an equally tenuous internal layer.

Occurrence.—Mesoproterozoic, Wood Duck Member of the Mainoru Formation, Roper Group, Australia.

Description.—Spheromorph with very thin chagrinate wall and small sinuous folds, and one lanceolate fold predominantly near the margins of compressed vesicles. Size 3–93 µm in minimum diameter (mean: 28.7 µm, σ = 16.8 µm, N = 149). Two specimens oval shaped (52–104 µm long and 32–64 µm wide), and one specimen (27 µm in diameter) bears an elongate expansion (40 µm long x 8 µm wide) (Fig. 2.3). Division by budding, with cells staying attached and forming irregular colonies, cells rarely isolated, often attached to one to four other cells, commonly with large spherical scars left by detaching buds or adjacent cells. Range of diameter and morphology may vary greatly, from spherical to oval to filamentous. Commonly, taphonomic alteration results in the thin wall peeling off the vesicle from an equally tenuous internal layer.

Materials.—149 specimens measured, as clustered populations in basinal facies (samples U5 581.9m and 569.1m in the Wood Duck Member of the Mainoru Formation).

Remarks.—The Roper population forms an essentially monospecific assemblage in euxinic basinal shales, and is rare in other facies. It differs from Gemmuloides by the thin chagrinated wall, circular scars, and multiple attached buds forming colonies. It also differs from Eosaccharomyces ramosus Hermann, another budding spheromorph forming colonies, by the chagrinate ornamentation of the vesicle wall, and taphonomic features such as circular scars (Fig. 2.4) and one large lanceolate fold at periphery and very thin folds more centrally distributed (Fig. 2.1, 2.10). The attachment to a biofilm reported and illustrated by Hermann (1990, pl. 14) and Hermann and Podkovyrov (2012) is not observed for the Roper population, although it is not mentioned as a diagnostic character (Jankauskas et al., 1989). Growth of oval cells oriented in the direction of the “branches” of the colony do occur in the Lakhanda material, as underscored by Knoll et al. (2006), but this is not always the case (see Hermann 1990, pl. 14, figs. 5, 7), and is not reported as a diagnostic criterion in Jankauskas et al. (1989). The chagrinate spheromorphs commonly show evidence of budding (Fig. 2.2–2.8), forming spheres (Fig. 2.6–2.8) or elongate extensions (Fig. 2.3), with up to seven specimens attached. Some specimens bear a distinct circular hole rimmed by a fold in the wall (with a diameter up to more than 60% of the vesicle diameter) (Fig. 2.4). Because budding specimens may bear this hole (Fig. 2.7), it cannot be interpreted as a pylome (excystment structure), but rather as a scar left when connected individuals detached. Commonly, the thin wall has partially peeled off, exposing the lighter inner side of the vesicle wall (Fig. 2.6). Cells can be isolated, or more commonly attached to 1 to 4 other cells (Fig 2.7). Blastanosphaira kokkoda differs also from other spheromorphs with chagrinate walls, such as L. obsuleta and L. atava, by its prominent budding habit and consequent colonial association, very thin wall, and circular scars.

The chagrinate appearance seems to be an ornamentation rather than taphonomic alteration, suggesting eukaryotic affinity. SEM shows a granular wall and occasional taphonomic holes (Fig. 2.11). Budding is also consistent with eukaryotic affinities, resembling yeast behavior, but detailed ultrastructural and microchemical analyses will be required to confirm the affinity of this population. Due to its budding without cells detaching and forming colonies, E. ramosus has been interpreted as a possible fungus (yeast-like) by Hermann and Podkovyrov (2012) or as social amoebae, although these are difficult to preserve as compressions (Porter, 2006), except in stages of their life cycle when they can produce cellulose walls. Interestingly, cells of the modern yeast Saccharomyces may bear several circular scars, and when budding rapidly, form pseudomycelia. However, budding as a form of asexual reproduction also occurs in some bacteria (cyanobacteria, prosthecate proteobacteria; Angert, 2005), in addition to some protists, fungi (yeast), and animals. The chagrinate ornamentation of the wall combined with large size suggest the Roper fossils are probable eukaryotes, and their common budding and pseudocolonial habit shows they represent metabolically active, reproducing vegetative cells. Their restricted distribution in deeper anoxic facies may suggest an anaerobic metabolism (see Muller et al., 2012 for a review of modern anaerobic eukaryotes) or facultatively aerobic metabolism at low oxygen tensions. Alternatively, they could have been planktonic, but in this case, their limitation to deeper anoxic facies is difficult to explain.

Type species.—Chlorogloeaopsis zairensis Maithy, 1975, from the Bushimay (now Mbuyi-Mayi) Supergroup, RDC, Meso-Neoproterozoic.

Other species.—Chlorogloeaopsis kanshiensis (Maithy, 1975), n. comb. Hofmann and Jackson, 1994; Chlorogloeaopsis contexta (Hermann, 1976) n. comb. Hofmann and Jackson, 1994.

1976 Polysphaeroides contextus Hermann in Timofeev, Hermann, and Mikhailova, p. 42, pl. 14, fig. 3

1989 Polysphaeroides contextus; Jankauskas et al., p. 119, pl. 27, figs. 10a, b

1990 Polysphaeroides contextus; Hermann, p. 26, pl. 8, fig. 8

1994 Chlorogloeaopsis contexta; (Hermann in Timofeev et al., 1976), emend. Hofmann and Jackson, p. 19, figs. 12.13–12.15

Holotype.—Polysphaeroides contextus Hermann, 1976 in Timofeev, Hermann, and Mikhailova, p. 42–43, pl. 14, fig. 3; from the late Riphean (Tonian) Miroedikha Formation of the Turukhan Uplift, Siberia.

Occurrence.—Mesoproterozoic and Neoproterozoic successions worldwide, such as the Mbuyi-Mayi Supergroup, RDC; the Miroedikha Formation of the Turukhan Uplift, Siberia; the Roper Group, Australia; the Bylot Supergroup, Canada.

Description.—One cylindrical colony without envelope, composed of several indistinctly defined rows of cells 3–5 µm wide; colony 400 µm long and 25 µm wide.

Materials.—One specimen from sample U6 240.2m, Mainoru Formation.

Remarks.—The spelling of the genus was corrected by Hofmann and Jackson (1994, p. 18–19) and simultaneously (both in July 1994) by Butterfield et al. (1994, p. 72). Hofmann and Jackson (1994) recognized three species of Chlorogloeaopsis: C. contexta (Hermann, 1976) n. comb. Hofmann and Jackson, 1994, has indistinct rows of cells and cell diameter ranging from 1 to 5 µm; C. zairensis Maithy, 1975 with cells 8 to 10 µm in diameter, two to four in a row, while C. kanshiensis has cells 10–15 µm in diameter, two or three distinct rows of cells. The Roper population differs from C. kanshiensis, defined by two or three rows of cells, and from Polysphaeroides spp., which are loose aggregates of spheroidal dispersed cells or pairs, tetrads, octads, and spheroidal colonies of up to 10–20 cells in a sheath.

Type species.—Coneosphaera inaequalalis Luo, 1991, from the Changlongshan Formation, Neoproterozoic, China.

Other species.—Coneosphaera artica Hofmann and Jackson, 1994; Coneosphaera sp. Hofmann and Jackson, 1994.

Description.—50–51 µm thin-walled light brown spheromorphs loosely associated with many smaller 2–4 µm vesicles on the wall surface and close to their periphery. Three specimens observed.

Materials.—Three specimens from sample U6 226.95 m, Mainoru Formation.

Remarks.—Our specimens differ from C. artica, which shows larger diameters of both large and small vesicles (79–130 µm and 8–11 µm, respectively) and a higher number of the loosely attached or closely associated small vesicles. It also differs from C. sp. in the Bylot Group (Hofmann and Jackson, 1994), which has a few vesicles firmly attached to a larger central one and resembles a specimen illustrated by Hermann (1990, p. 20, pl. 5.11) in the Miroedikha Formation, Siberia. It differs from C. inaequalalis, which is characterized by a large cell three or four times bigger than the attached smaller cells, and one cell much smaller than the others (Luo, 1991, p. 193).

Type species.—Dictyosphaera macroreticulata Xing and Liu, 1973, from the Chuanlingguo Formation, Yenliao region; Chih County of Hopei, northern China, Mesoproterozoic.

1973 Dictyosphaera macroreticulata Xing and Liu, p. 22, 58, pl. 1, 16–17.

1982 Dictyosphaera delicata; Hu and Fu, p. 108, pl. 2, figs. 3–6.

2001 Dictyosphaera sp.; Javaux et al., fig 1e.

2003 Dictyosphaera delicata; Kaufman and Xiao, fig. 1.

2005 Dictyosphaera delicata; Yin et al., p. 52, fig. 2.1, 2.2, 2.4, 2.5, 2.7, 2.9, 2.10.

2007 Dictyosphaera delicata; Yin and Yuan, p. 351, fig. 1.1.

2009 Dictyosphaera delicata; Schiffbauer and Xiao, fig. 3f.

?2011 “ellipsoidal vesicle with a micro-reticulate wall” Strother et al., fig. 1i, j.

2015 Dictyosphaera macroreticulata; Agic et al., p. 32, figs. 2–4.

Lectotype.—Specimen originally described as Dictyosphaera sinica Xing and Liu, 1973, from the Chuanlingguo Formation, Yenliao region, Chih County of Hopei, northern China, Mesoproterozoic, and junior synonym of D. macroreticulata Xing and Liu (1973, pl. I:18) (Agic et al., 2015).

Occurrence.—Paleoproterozoic and Mesoproterozoic of China (Ruyang and Gaoshanhe Groups) (Xing and Liu, 1973), Australia (Roper Group) (Javaux et al., 2001), Belt Supergroup (Adam, 2014).

Description.—Only three specimens observed in the Roper population, one specimen measured: 50 µm in diameter with polygonal plates less than 2 µm wide. No excystment structure observed.

Materials.—Three specimens in basinal mudstones of the Velkerri Formation (sample GG1 48.75 m).

Remarks.—Agic et al. (2015) revised the taxonomy of the genus Dictyosphaera and synonymized all the species previously described (D. delicata, D. sinica, D. gyrorugosa, D. incrassata) to the senior species D. macroreticulata, described as 10 to 300 µm vesicles ornamented by a reticulate polygonal pattern consisting of interlocking 1–6 µm polygonal plates. Excystment by pylome or medial split. Because the holotype was not available for re-examination, they selected a lectotype from the same material as the holotype. In their original diagnosis, Hu and Fu (1982) described a reticulate surface ornamentation, but did not comment on its fine structure. TEM analysis by Yin et al. (2005) subsequently demonstrated that the wall is made of interlocked polygonal plates 1–3 µm wide, perforated by nanopores observed with SEM on both the exterior and interior vesicle surfaces (Kaufman and Xiao, 2003). The wall ultrastructure is multilayered (FIB-EM analyses; Schiffbauer and Xiao, 2009), and excystment by partial rupture or a circular opening (pylome) has also been observed (Yin et al., 2005).

Dictyosphaera macroreticulata is reported from the ~1580–1460Ma Lower Belt Group, USA (Adam, 2014), as well as the 1400–1700 Ma Ruyang and broadly correlative Gaoshanhe groups of China, where it co-occurs with abundant Shuiyousphaeridium macroreticulatum, an acanthomorph with similar wall ornamentation but bearing many processes (Xiao et al., 1997; Schiffbauer and Xiao, 2009). In the Chinese assemblages, Dictyosphaera specimens may include life cycle or taphonomic variants of Shuiyousphaeridium (Xiao et al., 1997) that either lost or never formed the outer wall layer from which processes arise (Javaux et al., 2004). The Chinese population includes vesicles ranging from 28 to 240 µm in diameter, with 1–4 µm platelets (Agic et al., 2015). In the Roper Group, however, D. macroreticulata (= D. delicata) is rare and Shuiyousphaeridium absent. Dictyosphaera possibly occurs, as well, in the ~1000Ma Stoer and lower Torridon groups, Scotland (Javaux, personal observation, 2008), although it is unnamed in Strother et al. (2011), who described a population as ellipsoidal fossils with walls made of highly ordered circular pits, creating a reticulate pattern and, therefore, differing from the plate-like wall structure of the Mesoproterozoic Dictyosphaera.

Kaufman and Xiao (2003) suggested that D. macroreticulata (= D. delicata) was a photosynthetic eukaryote based on its complex morphology and C-isotopic composition. Neither morphology nor isotopic composition, however, is diagnostic with respect to energy metabolism, although the eukaryotic nature of this ornamented acritarch is convincing. Functionally, D. macroreticulata is most likely a cyst or resting stage common to the life cycles of metabolically diverse eukaryotes (see below).

Recently, Tang et al. (2015) described a new species, D. tacita, based on two specimens that differ from the other species by their smooth external surface and the presence of hexagonal platelets only on the interior vesicle surface. The hexagons are smaller (0.5–0.9 µm) and the vesicle diameter larger (100–120 µm) than those of D. macroreticulata (2–6 µm platelets, 10–20 µm vesicle diameter), D. sinica (0.5–1.5 µm platelets, 15–45 µm vesicle diameter), and D. delicata (1–3 µm platelets, 50–300 µm vesicle diameter). However, Agic et al. (2015) proposed a synonymy among D. delicata, D. macroreticulata, and other species of the genus based on the overlapping size range of the vesicles and wall platelets, and similar morphologies. Tang et al. (2015) argued that this needs reevaluation.

Type species.—Eomicrocystis magilca Golovenok and Belova, 1986

Other species.—Eomicrocystis elegans Golovenok and Belova, 1986

1986 Eomicrocystis magilca Golovenok and Belova, p. 95 [English version p. 89], pl. 7., figs. 5–7.

1989 Eomicrocystis magilca; Jankauskas et al., p. 91, pl. 19, fig. 7.

1994 Eomicrocystis magilca; Hofmann and Jackson, p. 25, pl. 18, figs. 2–4.

1997 Eomicrocystis magilca; Cotter, p. 258, fig. 7A, B.

2016 Eomicrocystis magilca; Baludikay et al., 2016, p. 179, fig. 12f.

Holotype.—Eomicrocystis malgica Golovenok and Belova, 1986, pl. 7, fig. 5, from the Malgina Formation in the Uchur-Maya region, eastern Siberia.

Description.—Small ovoid or spheroidal colonies of light brown, loosely packed, small spheroidal to ovoid vesicles of uniform size, sometimes dividing by binary fission, without enclosing envelope. Three colonies observed, with cells 3 µm wide and 6–7 µm long.

Occurrence.—Mesoproterozoic and early Neoproterozoic, Roper Group, Australia; Malgina Formation in the Uchur-Maya region, eastern Siberia (Golovenok and Belova, 1986); Bylot Supergroup, Canada (Hofmann and Jackson, 1994); Belt Supergroup, USA (Adam et al., 2016); Mbuyi-Mayi Supergroup, RDC (Baludikay et al., 2016).

Materials.—Three colonies in samples U5 125.1m from the Jalboi Formation and U6 230.8m from the Mainoru Formation.

Remarks.—Eomicrocystis differs from the genus Coleogleba (Strother et al., 1983) in lacking an organic matrix or distinct envelope enclosing the cell clusters, and from the genus Coniunctiophycus by the absence of a single dense mass less than a micron in diameter within cells, the smaller cell size (10 µm in C. sp), and the shape of the colony described in the Belt Supergroup as “spheroidal colony of tens of individuals, from which a wide, linear extension of more cells emerges and folds back onto itself to form a single reticulate fold” (Adam et al., 2016, p. 16). It also differs from described species of Myxococcoides (Schopf, 1968) in the size and organization of constituent cells. Eomicrocystis malgica differs from E. elegans by the smaller size of the cells' minimum diameter (3–5 µm versus 6–9 µm) and more regular shape of the aggregate. The Roper colonies have cell diameters intermediate between the two species, but also have an irregular aggregate shape, and therefore are identified as E. malgica.

Type species.—Gemmuloides doncooki Samuelsson and Butterfield 2001

2001 Gemmuloides doncooki Samuelsson and Butterfield, p. 248, fig 7, D–F.

2014 Gemmuloides doncooki; Adam, p. 35, fig. 13.

Holotype.—Gemmuloides doncooki Samuelsson and Butterfield, 2001, p. 248, 249, GSC 117042 (Fig. 7D), Lone Land Formation, NW flank of Cap Mountain (63°24′11″N, 123°14′12″W), Canada, approximately 2m above carbonate ledge. Sample 94-LL-8. GSC loc. C-404520.

Description.—Two spheromorphs, 260 and 85 µm diameter, with chagrinate wall were observed, each with a dark central sphere; only one shows evidence of budding. The presence of a dark central body is not included in the original description, but this may reflect taphonomic rather than systematic differences. The presence of a bud allies the Roper fossils with Gemmuloides doncooki.

Occurrence.—Roper Group, Australia; Lone Land Formation, Canada (Samuelsson and Butterfield, 2001); Belt Supergroup, USA (Adam, 2014).

Materials.—Two adjacent specimens in samples A82/3 328.35m from the Jalboi Member and U6 240.2m from the Mainoru Formation.

Remarks.—The Roper assemblage includes another budding spheromorph, Blastanosphaira kokkoda, which differs from cf. G. doncooki by its colonial habit, smaller diameter, thinner chagrinate wall with thin folds, and multiple buds of larger size relative to the mother cell, as well as by the presence of circular scars left by detached buds. Coneosphaera sp. in the Bylot Group (Hofmann and Jackson, 1994) has several smaller vesicles attached to a central one, resembling a specimen illustrated by Hermann (1990, p. 20, pl. 5.11) from the Miroedikha Formation, Siberia, which also differs from cf. G. doncooki. Gemmuloides doncooki is also reported in the Belt Supergroup, Montana, USA (Adam, 2014).

Type species.—Leiosphaeridia baltica Eisenack, 1958.

Remarks.—Jankauskas (1989) revised the taxonomy of the genus Leiosphaeridia (see for detailed synonymy) and proposed an operational approach to species recognition within the genus Leiosphaeridia, essentially diagnosing species based on a combination of two characters: size and wall texture. Subsequent workers have tended to follow this scheme, with some modifications (e.g., Butterfield et al., 1994; Hofmann and Jackson, 1994). Jankauskas (1989) discriminated four smoothwalled Leiosphaeridia species: L. crassa and L. jacutica are thick-walled leiospheres, smaller or larger than 70 µm in diameter, respectively; L. minutissima and L. tenuissima are thin-walled vesicles, again smaller or larger than 70 µm in diameter, respectively. A fifth species, L. ternata differs from other species in having a distinctively rigid, opaque wall that fractures radially. Chuaria circularis is also a smooth-walled spheromorph, but can be discriminated from the leiospheres by its much thicker wall (at least 2 µm thick), concentric folds and wrinkles, and large diameter (0.43–3.5mm), leaving textured imprints on bedding surfaces (Butterfield et al., 1994).

The difficulty of applying the modified Jankauskas classification lies in the potential challenge of estimating wall thickness (underscored by Butterfield et al., 1994) and in classifying populations that do not fit neatly within the proposed size classes, as also noticed by Porter and Riedman (in press) in populations from the Neoproterozoic Chuar Group. Thus, while Butterfield et al. (2004) and Hofmann and Jackson (1994) reported a taxonomic break at 70 µm, there is little in the size frequency diagrams they present to justify this. Wall thickness has commonly been estimated on the basis of color or fold morphology, but wall color can vary as a function of taphonomy, thermal maturity, or original composition. Butterfield (in Butterfield et al., 1994, p. 11–12) has discussed the distinction between the thickness of folds and the thickness of the wall, which are not necessarily correlated. Previous study of wall ultrastructure in different Leiosphaeridia species from the Roper Group (Javaux et al., 2003, 2004) showed that L. crassa with thick lanceolate folds had a thinner wall than L. tenuissima with thin sinuous folds. We suggest that fold morphology, which reflects the taphonomy of walls with biological differences in flexibility, provides a more objective criterion than wall thickness or color. In this view, L. crassa and L. jacutica have thick lanceolate folds, whereas L. minutissima and L. tenuissima have thin sinuous folds.

Size frequency distribution presents a second complication, because many leiosphaerid populations transgress the 70 µm boundary taken to separate species. For example, we measured the minimum diameter of specimens of different color (dark brown, medium brown, light brown) and fold morphology (broad lanceolate or thin sinuous folds) within the Roper assemblage and observed no size break around 70 µm in these different morphotypes (Figs. 3.1–3.7, 4.4–4.8). This difficulty has also been underlined by Porter and Riedman (2016) for Chuar Group populations. We suggest that species should be distinguished on the basis of modal rather than maximum diameter, so that Leiosphaeridia with lanceolate folds and a modal size <70 µm would be assigned to L. crassa, whereas populations with lanceolate folds and a modal size >70 µm would be placed in L. jacutica. This has the advantage of removing ambiguity in size frequency distributions while retaining the species distinctions used in many previous publications.

Based on the presence of a multilayered recalcitrant wall, Roper leiospheres have been interpreted as eukaryotic (Javaux et al., 2004). In the absence of supporting TEM analyses of wall ultrastructure, this attribution cannot be extended to all Proterozoic leiospheres; very likely the genus Leiosphaeridia is polyphyletic and their simple morphologies may record both prokaryotes and eukaryotes. Occasionally, medial split excystment structures have been observed in Roper specimens, suggesting that at least some of these fossils were resting cysts; however, even here, caution is advisable, because baeocyte-producing cyanobacterial cells can split in ways that resemble medial split excystment (Waterbury and Stanier, 1978, p. 13, fig. 4).

Leiospheres may occur as isolated specimens assigned to Leiosphaeridia, compact colonies called Synsphaeridium spp., or loose colonies named Symplassosphaeridium spp., possibly reflecting cyst and vegetative stages of the same population or life stages of different organisms. Single leiospheres might also be detached specimens from a colony (Hofmann and Jackson, 1994). The simple morphologies of leiospheres make it difficult to choose among these hypotheses, but more detailed analyses of wall ultrastructure and chemistry may provide the requisite tests (Javaux et al., 2004; Javaux and Marshall, 2006).

1960 Megasacculina atava Naumova, pl. 3, fig. 15.

1989 Leiosphaeridia atava (Naumova, 1960); Jankauskas et al., p. 74, pl. 10, figs. 4–7.

2016 Leiosphaeridia atava; Sergeev et al., fig. 4.5.

Holotype.—Preparation 452/1, paleontological collection at the Institute of Precambrian Geology and Geochronology, St. Petersburg, Russia, upper Riphean (Tonian), Lakhanda Group, Neryuen Formation, Uchur-Maya region, Siberia. (The holotype was lost, as mentioned by Sergeev and Lee, 2006).

Occurrence.—The Mainoru Formation, Roper Group, Australia; the Lakhanda Group, Neryuen Formation, Uchur-Maya region, Siberia (Jankauskas, 1989); the Koltasy Formation, Russia (Sergeev et al., 2016); the El Mreiti Group, Taoudeni Basin, Mauritania (Beghin et al., in review).

Description.—Spheroidal to oval vesicle with a fine granular, flexible wall, with numerous folds, 46 to 56 µm in diameter (N = 4); two specimens with a dark, internal bleb of organic matter. No excystment structures observed.

Materials.—Four specimens observed in sample U6 230.8m from the Mainoru Formation.

Remarks.—Leiosphaeridia atava differs from L. obsuleta by its diameter larger than 70 µm (Jankauskas, 1989).

1949 Leiotriletes crassus Naumova, p. 54, pl. 1, figs. 5, 6; pl. 2, figs 5, 6.

1989 Leiosphaeridia crassa; Jankauskas in Jankauskas et al., p. 75, pl. 9, figs. 5–10.

1989 Leiosphaeridia minutissima; Jankauskas et al., p. 75, pl. 9, figs. 2, 3.

Holotype.—No holotype was designated by Naumova (1949), from the Lontova Formation, lower Cambrian, Estonia. A lectotype was designated by Jankauskas (in Jankauskas et al., 1989, p. 75) from Naumova (1949, pl. 1, fig. 3), but this specimen was part of Leiotriletes simplicissimus, which is a species that Jankauskas et al. (1989) synonymized with a different species of L. minutissima (Porter and Riedman, 2016).

Emended diagnosis.—A species of Leiosphaeridia with smooth, pliant walls with lanceolate folds and a modal diameter of less than 70 µm.

Occurrence.—Proterozoic and lower Paleozoic, worldwide.

Description.—Smooth-walled leiospheres with large lanceolate folds (Fig. 3.1–3.4). Minimum diameter ranges from 5 to 390 µm (mean: 58.1 ±40.2 µm, N = 669). No statistical differences among dark brown, medium, and light brown subpopulations, with mean diameters and standard deviations of, 54.5± 21.6 µm (N = 61), 55.3 ±30.7 µm (N = 191 µm), and 56.0± 27.7 µm (N = 116). Excystment by partial rupture and medial split.

Materials.—These are the most common microfossils in the Roper assemblage, especially in samples U6 305.1m from the Mainoru Formation and U5 125.1m from the Jalboi Member.

Remarks.—As noted above, the rationale for emending the diagnosis of this species stems from the desire to focus on observed rather than inferred wall characters and to articulate size distinctions in a way that will minimize ambiguity in observed populations. The emended diagnosis considers the presence of lanceolate folds on a smooth wall as a diagnostic character as opposed to the wall color, which is not considered as a valid character.

1966 Kildinella jacutica Timofeev, p. 30, pl. 7, fig. 2.

1989 Leiosphaeridia jacutica (Timofeev, 1966); Mikhailova and Jankauskas in Jankauskas et al., 1989, p. 77, pl. 9, fig. 12; pl. 12, figs. 3, 6, 7, 9.

Holotype.—Preparation number 452/1, Biostratigraphy Laboratory, Maya River Collection, late Mesoproterozoic/early Neoproterozoic Lakhanda Group, Russia (Timofeev, 1966, pl. 7, fig. 2).

Emended diagnosis.—A species of Leiosphaeridia characterized by smooth, pliant walls with lanceolate folds and a modal diameter greater than 70 µm.

Occurrence.—Proterozoic worldwide.

Description.—A species of Leiosphaeridia characterized by smooth, pliant walls with lanceolate folds and a modal diameter greater than 70 µm. Excystment by partial rupture and medial split. While we cannot exclude the possibility that these represent a long right-hand tail of the L. crassa population, we suspect that, by comparison to other mid-Proterozoic assemblages, distinct populations of large leiosphaerids were present in the Roper seaway.

Materials.—The Roper assemblage contains a relatively small proportion of very large, smooth walled leiosphaerids, in samples U6 305.1m and 240.2m from the Mainoru Formation and sample GG1 326.2m from the Corcoran Formation.

Remarks.—As noted above, the rationale for emending the diagnosis of this species stems from the desire to focus on observed rather than inferred wall characters and to articulate size distinctions in a way that will minimize ambiguity in observed populations. The emended diagnosis considers the presence of lanceolate folds on a smooth wall as a diagnostic character, as opposed to wall color, which is not considered as a valid character.

1949 Leiotreletes minutissimus Naumova, p. 52, pl. 1, figs. 1, 2; pl. 2, figs. 1, 2.

1989 Leiosphaeridia minutissima (Naumova); Jankauskas in Jankauskas et al., p. 79, pl. 9, figs. 1, 4, 11.

Lectotype.—No holotype was designated by Naumova (1949). Jankauskas (in Jankauskas et al., 1989, p. 80) designated a specimen of Leiotriletes minutissimus (pl. 1, fig. 1) from Naumova (1949) as lectotype.

Emended diagnosis.—A species of Leiosphaeridia characterized by smooth walls with sinuous folds and a modal diameter less than 70 µm.

Description.—Smooth-wall spheromorphs with sinuous folds and a modal diameter less than 70 µm. Minimum diameter 21–117 µm (mean: 50.6 ±18.2 µm, N = 216) (Figure 3.5–3.7). Light brown specimens 21–117 µm in minimum diameter (N = 116, mean: 50.8± 17.9 µm) and medium brown specimens 27–111 µm (N = 47, mean: 49.6± 19.1 µm). No dark brown specimens observed.

Occurrence.—Proterozoic worldwide.

Materials.—Common in inshore facies of the Roper Group, especially in samples U6 305.1 m, and U6 273.7m from the Mainoru Formation.

Remarks.—As noted above, the rationale for emending the diagnosis of this species stems from the desire to focus on observed rather than inferred wall characters and to articulate size distinctions in a way that will minimize ambiguity in observed populations. The emended diagnosis considers the presence of sinuous folds on a smooth, thin wall as a diagnostic character, as opposed to wall color, which is not considered as a valid character.

1958 Leiosphaeridia tenuissima Eisenack, p. 391, pl. 1, figs. 2, 3.

1989 Leiosphaeridia tenuissima; Jankauskas et al., p. 81, pl. 9, fig. 13.

Holotype.—Preparation A3, 3 number 4 from the Dictyonemashales of the lower Ordovician, St Petersburg area, Russia (Eisenack, 1958, pl. 1, fig. 2).

Emended diagnosis.—A species of Leiosphaeridia characterized by smooth walls with sinuous folds and a modal diameter (rather than maximum diameter) greater than 70 µm; the wall color is not a diagnostic criteria.

Description.—Smooth wall spheromorphs with sinuous folds and a modal diameter greater than 70 µm. These may reflect a larger, uncommon population of Leiosphaeridia in Roper shales.

Occurrence.—Proterozoic worldwide.

Materials.—Uncommon specimens in samples U6 305.1m and U6 230.8m from the Mainoru Formation.

Remarks.—As noted above, the rationale for emending the diagnosis of this species stems from the desire to focus on observed rather than inferred wall characters and to articulate size distinctions in a way that will minimize ambiguity in observed populations. The emended diagnosis considers the presence of sinuous folds on a smooth, thin wall as a diagnostic character as opposed to wall color, which is not considered as a valid character.

1966 Turuchanica ternata Timofeev, p. 45, pl. 9, fig. 8.

1989 Leiosphaeridia ternata (Timofeev); Mikhailova and Jankauskas in Jankauskas et al., p. 81, pl. 11, figs. 2–4; pl. 12, figs. 4, 5, 8.

2016 Leiosphaeridia ternata; Sergeev et al., fig. 4.3, 4.4.

Holotype.—Preparation 169/1, Biostratigraphical laboratory LAGED AN SSSR, Turukhansk collection, lower Tungunska, Turukhansk district; Miroedikhinsk series, Riphean (Mesoproterozoic and early Neoproterozoic boundary), rarely Ordovician (Timofeev, 1966).

Occurrence.—Found globally in worldwide Proterozoic successions.

Description.—Compressed opaque spheromorph with thick, rigid walls commonly showing characteristic radial fractures. Diameter 15 to 110 µm.

Materials.—A few specimens were observed in samples A82/3 157.5m in the Jalboi Member, GG1 326.2m in the Corcoran Formation, and U6 305.1m in the Mainoru Formation.

Description.—Large medium to dark brown spheroidal to oval vesicles with a characteristic cork-like wall texture made of 5–11 µm, irregular patchy areas of different colors and fabric; this texture may well be taphonomic, but if so, it reflects original differences in wall composition, compared to other leiosphaerids. Concentric folds at the periphery. The minimum diameter of 19 spheroidal specimens is 56–455 µm (mean: 159.8± 96.3 µm). Three oval specimens measured 75–210 µm wide and 160–330 µm long.

Materials.—22 specimens in the Gibb Member, samples U6 305.1 m, U6 230.8m of the Mainoru Formation, and in sample GG1 171.5m of the Corcoran Formation.

Remarks.—This species differs from another large leiosphere L. jacutica by its particular cork-like wall texture and a morphology that ranges from spheroidal to ovoidal. It also differs from Chuaria circularis, which has a thicker opaque, smooth wall. These specimens are left in open nomenclature until further characterization by SEM and TEM.

Type species.—Lineamorpha elongata Vorob'eva, Sergeev, and Yu, 2015, by monotypy.

2004 “large striated tubes” Javaux et al., p. 126, fig 3 g–k.

2015 Lineamorpha elongata; Vorob'eva et al., p. 216, figs. 7 1–7.5.

2016 Lineamorpha elongata; Adam et al., fig. 9 A–D.

Holotype.—Figure 7.4, Vorob'eva et al., 2015, GINPC 14711-804, locality AK-14, Kotuikan River valley, Kotuikan Formation, Anabar Uplift, northern Siberia.

Occurrence.—Early Mesoproterozoic, Jalboi, Crawford, and upper Mainoru formations, Roper Group, Australia; Belt Supergroup, Montana, US (Adam, 2014); and Kotuikan Formation, northern Siberia (Vorob'eva et al., 2015).

Description.—Longitudinally striated hollow tubes (not a sheath around bundled filamentous sheaths) that often break into fragments, so maximum length is unknown but millimetric, 34 to 150 µm in diameter, fragment length: 131 to 473 µm (N = 25).

Materials.—562 specimens observed in maceration, in lowershoreface to inner shelf facies of the Jalboi, Crawford, and upper Mainoru formations, Roper Group; one observed in thin section, 25 measured specimens. Abundant specimens observed in samples U5 125.1m and U5 151.3m of the Jalboi Member; in samples U5 334.3m and U5 412.1m of the Arnold sandstone Member; in samples A82/3 311m of the Crawford Formation; and in samples U6 305.1 m, U6 230.8 m, and U6 240.2m from the basal Mainoru Formation, but rare elsewhere.

Remarks.—In the Roper population, there seems to be no relation between diameter and fragment length, nor dominant fragment length, suggesting random fragmentation of longer, probably millimetric, tubes. Light microscopy shows longitudinal, micron-scale striations along the tubes while SEM reveals a thick multilayered wall of densely packed granules, but no longitudinal striations. At the ultrastructural level (TEM), however, transverse sections of the wall show a clear alternation of electron-dense and electron-tenuous bands that correspond in size and distribution to the striations observed by light microscopy (Javaux et al., 2004). The wall is ~1 µm thick, occasionally with an outer, electron-dense layer. The striations, thus, are not wall sculpture, but reflect original compositional heterogeneities in the tube wall, indicating complex physiological controls on wall formation.

The Roper material appears to be indistinguishable from the type of Lineaforma elongata from the lower Mesoproterozoic Kotuikan Formation, northern Siberia (Vorob'eva et al., 2015). In the Roper Group, these filaments occur as transported fragments, contributing less than 3% to the entire assemblage, but up of 40% in lower-shoreface to innershelf shales. The rounded, closed tube ends observed in the Russian population were not observed in fragmental Roper specimens. The large size and complex wall ultrastructure of these microfossils suggest a eukaryotic affinity (Javaux et al., 2004).

Type species.—Palaeolyngbya barghoorniana Schopf, 1968

1974 Palaeolyngbya catenata Hermann, p. 8, pl. 6, fig. 5.

1980 Oscillariopsis robusta; Horodyski and Donaldson, p. 149, fig. 13H.

1994 Palaeolyngbya catenata; Butterfield et al., 1994, p. 61, fig. 25F–G.

Holotype.—No holotype designated by Hermann, 1974, p. 8, 9, pl. 6, fig. 5, Tonian, Miroedikha Formation, Russia.

Description.—Cellular trichome within a single encompassing sheath, cells 26 µm wide and 6 µm long.

Materials.—One fragmented specimen with ripped sheath in sample U5 130.5m from the Jalboi Member.

Type species.—Satka favosa Jankauskas, 1979a

1979a Satka favosa Jankauskas, pl. 4, fig. 2.

1980 “polygonally segmented sphaeromorphs” Horodyski, p. 658, pl. 2, figs. 8–12.

1989 Satka favosa; Jankauskas et al., p. 51, pl. 4, figs. 1, 2?

1989 Satka elongata; Jankauskas et al., p. 51, pl. 4, figs. 3, 5.

1989 Satka granulosa; Jankauskas et al., p. 51, pl. 4, fig. 8.

1994 Satka spp. Hofmann and Jackson, pl. 18, figs. 26–31.

2001 Satka favosa; Javaux et al., pl. 1e, f.

2003 Satka favosa; Javaux et al., figs. 1–10, 11.

2004 Satka favosa; Javaux et al., 2004, p. 125, fig. 3a–f.

Holotype.—Specimen pl. 4, fig. 2, preparation 16-1815-635, lower and middle Riphean (Mesoproterozoic) successions of the southern Urals, Russia (Jankauskas, 1989).

Description.—Hollow oval spheromorph, 24 to 100 µm wide and 29 to 100 µm long (N = 122), with walls made of tessellated 6 to 16 µm (minimum diameter) polygonal plates and with no external envelope. Excystment by medial split (Fig. 5.6).

Occurrence.—Satka favosa, as described here, seems to be restricted to Mesoproterozoic rocks, including lower Mesoproterozoic shales of the Belt Supergoup (“polygonally segmented sphaeromorphs” of Horodyski, 1980; Adam, 2014), the Bylot Supergroup of the Canadadian Arctic (Hofmann and Jackson, 1994, as Satka spp., pl. 18, figs. 26–31), and lower and middle Riphean (Mesoproterozoic) successions of the southern Urals (Jankauskas et al., 1989).

Materials.—Many specimens observed in shoreface facies of the Gibb Member, basal Mainoru Formation (samples U6 240.2 m, U6 273.7 m, U6 305.1 m), but rare elsewhere.

Remarks.—The wall construction of S. favosa identifies it as a eukaryote, most likely the resting stage of some protist. Great confusion exists in the literature concerning Satka and its species. Jankauskas (1989) differentiated S. favosa from S. elongata (40–70 µm) by its smaller size and the characteristic shape of its inward-curving plates; S. colonialica (up to 150 µm) was segregated because of its simpler regular shape and betterdefined plates; and S. granulosa (40–50 µm wide to 75–125 µm long) was differentiated by its smaller size and granular appearance (linked to the presence of internal bodies). The specimens illustrated by Jankauskas (1989) as Satka elongata (pl. 4, figs. 3, 5) and Satka granulosa (pl. 4, fig. 8) also resemble Satka favosa as described here. Satka squamifera is described as having rounded plates and an external envelope. From our observations, however, the “plates” of S. squamifera represent the imprints of spheroidal cells on an encompassing envelope; therefore, we interpret this population as a colonial microorganism, perhaps cyanobacterial, which is unlikely to be linked to S. favosa at the domain level, and recently placed within the new genus Squamosphaera (Tang et al., 2015).

Type species.—Siphonophycus kestron Schopf (1968).

Occurrence.—Widespread in Proterozoic assemblages, common throughout the Roper Group.

Description.—Fragments of smooth, non-septate tubes, commonly interpreted as the sheaths of oscillatorialean cyanobacteria.

Remarks.—Different species are distinguished on the basis of cross-sectional diameter (revision in Butterfield et al., 1994): S. thulenema: 0.5 µm; S. septatum: 1–2 µm; S. robustum: 2–4 µm; S. typicum: 4–8 µm; S. kestron: 8–16 µm; and S. solidum: 16–32 µm. Five species occur in Roper shales: S. kestron, S. robustum, S. septatum and S. typicum occur as transported fragments; and S. thulenema forms small balls of thin filamentous sheaths. Siphonophycus spp. are commonly interpreted as the sheaths of oscillatorialean cyanobacteria.

1968 Siphonophycus kestron Schopf, p. 671, pl. 80, figs. 1–3.

1971 Siphonophycus kestron; Schopf and Blacic, pl. 109, figs. 3, 4.

1992 Siphonophycus kestron; Sergeev, p. 95, pl. 16, figs. 8, 9.

1992 Siphonophycus kestron; Schopf, pl. 31, fig. J.

1994 Siphonophycus kestron; Butterfield et al., fig. 21D.

2001 Siphonophycus kestron; Sergeev and Lee, p. 8, pl. 1, fig. 1

2006 Siphonophycus kestron; Sergeev and Lee, pl. 1, fig. 10.

2006 Siphonophycus kestron; Sergeev, p. 214, pl. 22, figs. 1, 2; pl. 28, fig. 3; pl. 36, fig. 3; pl. 44, fig. 11; pl. 45, figs. 3, 6.

Holotype.—Specimen pl. 80, fig. 1 (Schopf, 1968), thin section Bit. Spr. 6-3, Paleobotanical Collections, Harvard University number 58469, from Neoproterozoic Bitter Springs Formation, Amadeus Basin, Australia.

Description.—Fragments of smooth, non-septate tubes, 8–16 µm in diameter, most specimens 8–9 µm, a few up to 16 µm.

Materials.—Dozens of filamentous sheaths, abundant in samples GG1 340.2m of the Corcoran Formation, a few in sample GG1 48.75m from the Velkerri Formation.

1968 Eomycetopsis robusta Schopf, p. 685, pl. 82, figs. 2–3; pl. 83, figs. 1–4.

1991 Siphonophycus robustum; Knoll et al., p. 565, fig. 10.3, 10.5.

1994 Siphonophycus robustum; Butterfield et al., p. 64, figs. 26A, G.

Holotype.—Specimen pl. 83, fig. 1 (Schopf, 1968), thin section Bit. Spr. 10-1, Paleobotanical Collections, Harvard University number 58491 from Neoproterozoic Bitter Springs Formation, Amadeus Basin, Australia.

Description.—Smooth filamentous sheaths 2–4 µm in diameter, most specimens 2–3 µm in diameter.

Materials.—Dozens of specimens, most abundant in sample GG1 340.2m of the Corcoran Formation and sample U6 240.6m of the Mainoru Formation.

1968 Tenuofilum septatum Schopf, p. 679, pl. 86, figs. 10–12.

1991 Siphonophycus septatum; Knoll et al., p. 565, fig. 10.2.

Holotype.—Specimen pl. 86, fig. 11 (Schopf, 1968), thin section Bit/Spr 6–3, Paleobotanical collections, Harvard University, number 58527 from the Neoproterozoic Bitter Springs Formation, Amadeus Basin, Australia.

Description.—Fragments of smooth, non-septate tubes, 1–2 µm in diameter. Common, as transported fragments.

Materials.—Common in the Roper Group, abundant in sample U5 508.6m of the Mainoru Formation.

1994 Siphonophycus thulenema Butterfield et al., fig. 22I.

Holotype.—HUPC 62718, fig. 22I, slide 86-G-62-46, R-28-3, Algal Dolomite Member, Svanbergfjellet Foramtion, Geerabukta (79°35′30″N, 17°44″E), 55m above base of member.

Description.—Fragments of thin, smooth, non-septate tubes, 0.5 µm in diameter, forming small balls of enrolled filamentous sheaths.

Materials.—Rare, in sample U5 125.1m of the Jalboi Member.

1974 Leiothrichoides tipicus Hermann, p. 7, pl. 6, figs. 1–2.

1994 Siphonophycus typicum; Butterfield et al., p. 66, figs. 23B–D, 26B, H, I.

Holotype.—Specimen pl. 6, figs. 1, 2 (Hermann, 1974), preparation number 49/2T, Neoproterozoic Miroyedikha Formation, Krasnoyarsk Krai in Turukhansk region, near Maya River, Siberia.

Description.—Fragments of thin smooth, non-septate tubes, 4–8 µm in diameter.

Materials.—Common; most abundant in samples U5 508.6m of the Mainoru Formation, GG1 46.75m of the Velkerri Formation and GG1 340.2m of the Corcoran Formation.

Type species.—Squamosphaera colonialica (Jankauskas, 1979b) Tang et al., 2015 by monotypy

1979b Satka colonialica Jankauskas, p. 192, pl. 1, figs. 4, 6.

1985 Satka colonialica; Knoll and Swett, p. 468, pl. 53, figs. 4–6, 8.

1989 Satka colonialica; Jankauskas et al., p. 51, pl. 4, figs. 4, 7.

1989 Satka squamifera; Jankauskas et al., p. 52, pl. 4, fig. 10; pl. 5, fig.1–8

1997 Satka colonialica; Samuelsson, p. 175, fig. 9A, B.

1999 Satka colonialica; Cotter, p. 77, fig. 7C.

1999 Satka colonialica; Samuelsson et al., fig. 4G.

2015 Squamosphaera colonialica; Tang et al., 2015, p. 312, fig. 12 A–C2, fig. 13 A–F2

in press Squamosphaera colonialica; Porter and Riedman, fig. 17, 1–7. [See for complete synonymy]

Holotype.—Number 16-62-4762/22, slide 1. Well Kabakovo-62, 4762-4765 m. Neoproterozoic Zigazino-Komarovo Formation, Ufa, Bashkirian Urals (Jankauskas, 1979, fig. 4).

Description.—Single-walled, spheroidal, tomaculate, or irregularly shaped vesicles with irregular outline characterized by numerous broadly domical bulges. Vesicles 29–166 µm wide and 66–184 µm long (N = 37); individual bulges 11 to 14 µm in diameter.

Materials.—Many specimens were observed in all facies except the most basinal and are particularly abundant in the lowershoreface to storm-dominated shelf facies of the Jalboi Member and Crawford Formation (samples A82/3 311 m, A82/3 166 m, U5 125.1 m, U5 151.3 m, U5 334.3 m, U5 412.1 m).

Remarks.—The Roper population closely matches the emended diagnosis provided by Porter and Riedman (in press). Populations assigned here to the genus Squamosphaera were originally classified as a species of the genus Satka (Jankauskas, 1979b). As discussed above, the type species of Satka, S. favosa, is characterized by a wall of tessellated plates, which is far different from the vesicles observed in S. colonialica. The two species should not be placed in the same genus and doubtfully belong to the same domain. Tang et al. (2015) gave formal recognition to this by segregating populations of Satka colonialica into the new genus. Tang et al.'s (2015) diagnosis and description suggest that Squamosphaera was a cyst wall ornamented by broadly domical processes, but this conflicts with the irregular morphology of individual vesicles, both within Tang et al.'s (2015) illustrated materials and populations observed elsewhere. For this reason, Porter and Riedman (in press) emended the diagnosis of Squamosphaera, identifying the domical surface features simply as bulges. Roper populations closely resemble those from the Chuar Group, and we interpret them as enveloped marked by imprints of internal cells no longer present.

Hofmann and Jackson (1994, p. 28) described Satka colonialica from the Bylot Supergroup, the Canadadian Arctic, as a colony of packaged cells in “distinct belt-like rows transverse to the long axis of the colony,” with a smooth surface and distinct curvilinear folds. They further suggested that S. squamifera, S. granulosa, and S. elongata might be taphonomic variants of the same taxon, and mentioned S. elongata Jankauskas, 1989 as the senior synonym to which other species should be referred. Satka favosa, however, is actually the senior species of the genus Satka (Jankauskas, 1979b). Hofmann and Jackson (1994) also include in their suggestion of synonymy a Bylot population referred to Satka spp. that we interpret as S. favosa (see above). Several types of coccoidal cyanobacteria (Chroococcales and Pleurocapsales) and green algae (such as Pandorina) can produce colonies of packed spheroidal cells embedded in an envelope of amorphous mucilage matrix. Less commonly, the individual cells have a single wall rather than a multilamellate envelope, are closely packed, and the colony is surrounded in a structurally defined envelope, such as in modern cyanobacteria that produce baeocytes (endospores) within a parental wall (Chroococcidiopsis and Staniera/Dermocarpa). Squamosphaera colonialica resembles these pleurocapsalean cyanobacteria, with the internal cells not preserved, only their imprints on the wall. Squamosphaera differs from Synsphaeridium spp., which are colonies without an envelope.

Description.—Aggregates of loosely packed, smooth-walled vesicles of variable size, but with similar morphology and size within a colony. Differs from Synsphaeridum by the loose packing of vesicles.

Materials.—Dozens of colonies observed.

Type species.—Synsphaeridium gotlandicum Eisenack, 1965.

Occurrence.—Widespread in Proterozoic and Phanerozoic rocks.

Description.—Aggregates of contiguous smooth-walled vesicles, sometimes with internal inclusions, without envelope. Vesicles are similar in morphology and size within a colony. Colonies have variable size, from broadly spherical to elongated and irregular. Cell diameter ranges from 4 to 40 µm, and colonies can be up to 180 µm or more in diameter.

Materials.—Dozens of colonies observed, especially in samples GG1 326.2 m, in the Corcoran Formation and in samples U5 125.1m and U5 151.3m of the Jalboi Member.

Type species.—Tappania plana Yin, 1997.

Other species.—Tappania tubata Yin, 1997; Tappania gangaei Prasad and Asher, 2001.

1997 Tappania plana Yin, p. 23, pl. 1, figs. 4, 6, 7.

1997 Tappania tubata Yin, p. 23, 24, pl. 2, figs. 1, 3, 4, 6.

1997 Tappania plana; Xiao et al., p. 205, fig. 3c.

2001 Tappania plana; Prasad and Asher, p. 73, pl. 2, figs. 1–3, 9; pl. 3, figs. 1–6.

2001 Tappania tubata; Prasad and Asher, p. 74, pl. 2, figs. 4–7.

2001 Tappania gangaei; Prasad and Asher, p. 74, pl. 2, figs. 8, 10.

2001 Tappania plana; Javaux et al., pl. 1a–c.

2004 Tappania plana; Javaux et al., p. 124, fig. 2a–e.

2009 Tappania plana; Nagovitsin, fig. 2 a–e.

Holotype.—Sample and slide M 9208-1, L4/37, Shuiyou section, southern Shanxi, North China; lower shales of Beidajian Formation of the Ruyang Group (Meso-Neoproterozoic) (Yin, 1997, pl. 1, fig. 7).

Description.—Size 15 to 158 µm (N = 48), irregularly spheroidal vesicle bearing zero to 21 tubular, heteromorphic, sometimes branching, sometimes septate processes with closed relatively dark, rounded ends; zero to four neck-like expansions; zero to three bulbous protrusions. Process length up to 8 µm; bulbous expansions 2 µm wide; neck up to 2 µm high and 2 µm wide; two specimens show septate processes (Fig. 6.2–6.4), two others with branching processes. One specimen with a neck-like expansion shows a concentration of small (~8 µm long) processes with dark ends in one area of the vesicle surface, and another has small (3–5 µm long), hair-like spines, which are probably developing processes (not shown). The vesicle occasionally includes a dark cytoplasmic remnant. Specimens may bear only broad neck-like extensions (Fig. 6.6, 6.7, 6.10), or only processes (zero to 21) (Fig. 6.2, 6.5, 6.9, 6.13), or both. Neck-like extensions usually have a dark rim. In one specimen without processes, this trapezoidal extension is open, possibly indicating excystment (Fig. 6.15). Some specimens also show bulbous expansions suggestive of division by budding (Fig. 6.1); buds have semi-circular to oval convex morphology, whereas neck-like expansions have a trapezoidal shape, with side walls flaring outward and a convex end.

Occurrence.—Tappania plana seems to be restricted to uppermost Paleoproterozoic and Mesoproterozoic rocks, including, in addition to the Roper Group, Australia (Javaux et al., 2001); the Ruyang Group, China (Xiao et al., 1997; Yin, 1997); the Bahraich and Kheinjua groups, India (Prasad and Asher, 2001; Prasad et al., 2005); the Kamo Group of Siberia (Nagovitsin 2009; Nagovitsin et al., 2010); and the Lower Belt Group, USA (Adam, 2014).

Materials.—48 specimens measured in samples, U5 151.3m and U5 130.5m from the Jalboi Formation (proximal shelf facies), and from GG1 340.2m and GG1 326.2m from the Corcoran Formation (TST, distal shelf facies).

Remarks.—We observed a wide range of morphologies within Tappania, ranging from specimens with only broad, neck-like extensions, or only processes, to individuals with both broad, neck-like extensions and processes. On one fragmented specimen bearing a neck-like expansion, very small processes with dark, rounded closed ends are locally grouped on the vesicle wall. This is the first time this morphology has been reported in Tappania plana, however a single fragmented specimen and the large variability of the species precludes the creation of a new species at this time. Rare specimens show processes with septa, suggesting Tappania was multicellular. Ultrastructural analyses show a unilayered homogenous wall (Javaux et al., 2004). The Roper population shows division by budding, and possible excystment through the opening of a neck-like extension. Specimens from the Kotuikan Formation illustrated by Nagovitsin (2009) suggest that Tappania could also reproduce by a simple binary division of the vesicle.

Yin (1997) described a second species of Tappania, T. tubata, that co-occurs with T. plana and has a broad tubelike extension but not trapezoidal neck-like extension, with a fimbriate distal margin and a few small processes on its extension surface. The Roper Tappania population displays the range of morphological characters originally ascribed to T. plana and T. tubata, occasionally on a single specimen. Therefore, we consider T. tubata to be a synonym of the senior species, Tappania plana. Prasad and Asher (2001) described a third species, Tappania gangaei, based on the rounded bulbous extension, rather than trapezoidal or tube-like. However, in the Roper population, specimens may bear both neck-like and rounded extension (interpreted as budding structures), therefore here too, we consider T. plana as the senior synonym.

Vesicles bearing neck-like expansions but no processes are reported as cf. Tappania? in the late Mesoproterozoic—early Neoproterozoic Mbuyi-Mayi Supergroup, RDC (Baludikay et al., 2016). However, the absence of processes on any of the six specimens observed so far and the younger age of these fossils leaves this occurrence ambiguous, even though Tappania populations elsewhere also include similar morphologies without processes. Indeed, so far, Tappania plana seems to be restricted to uppermost Paleoproterozoic to Mesoproterozoic rocks. Butterfield (2005a) described specimens from the mid-Neoproterozoic Wynniatt Formation, the Canadian arctic as Tappania, but these show a complex pattern of septation, peripheral branching and anastomosis not found in Mesoproterozoic populations and lack the neck-like expansions or the closed and rounded process terminations characteristic of older fossils. Therefore, the Neoproterozoic population might usefully be placed into a separate genus.

Type species.—Tortunema wernadskii (Schepeleva, 1960) Butterfield et al., 1994.

Description.—Fragmental remains of compressed cylindrical sheaths, 250–300 µm long and 30 µm wide (N = 2), marked by thin, regularly spaced, transverse annulations that record cell boundaries of originally ensheathed trichomes. Spacing of prominent annulations 6 µm, commonly with less-pronounced annulations between them.

Materials.—Two specimens.

Discussion.—Pseudoseptate filaments, widely distributed in Proterozoic platform and inner-shelf shales, are generally interpreted as the empty sheaths of cyanobacteria (e.g., Jankauskas, 1989; Butterfield et al., 1994). These sheaths are larger than the type species of the genus, T. wernadskii (Schepeleva) Butterfield. Because they are rare, we have little sense of their size frequency distribution, so only identify them as Tortunema sp.

Type species.—Trachytrichoides ovalis Hermann in Timofeev et al., 1976.

Description.—Multicellular filaments with ovoid cells and thick intercellular septa, no external sheath, 157 µm long and 5 µm wide (N = 3), with individual ellipsoidal cells 5 µm wide x 6 µm long.

Materials.—Three filaments observed in sample U6 240.2m of the Mainoru Formation.

Remarks.—A rare component of the Roper Group, differs from other filamentous taxa by the oval shape of the cells and absence of ellipsoidal fold between the cells (as in Arctacellularia), and from the type species T. ovalis by the smaller cell size than those of the holotype (25–35 µm wide and 30–60 µm long).

Type species.—Valeria lophostriata (Jankauskas, 1979b) Jankauskas, 1982.

1979b Kildinella lophostriata Jankauskas, p. 153, fig. 1.13–1.15.

1982 Valeria lophostriata; Jankauskas, p. 109, pl. 39, fig. 2.

1983 Kildinosphaera lophostriata; Vidal and Siedlecka, p. 59, fig. 6A–G.

1985 Kildinosphaera lophostriata; Vidal and Ford, p. 361, fig. 4C, E–F.

1989 Valeria lophostriata; Jankauskas et al., p. 86, pl. 16, figs. 1–5. [See for additional synonymy]

1994 Valeria lophostriata; Hofmann and Jackson, 1994, p. 24, pl. 17, figs. 14–15; pl. 19, fig. 4.

1997 Valeria lophostriata: Xiao et al., p. 201, fig. 3e.

1999 Valeria lophostriata; Samuelsson et al., p. 15, fig. 8E.

2001 Valeria lophostriata; Javaux et al., fig. 1D.

2004 Valeria lophostriata; Javaux et al., fig. 2F–I.

2009 Valeria lophostriata; Nagy et al., fig. 1A, B.

2009 Valeria lophostriata; Nagovitsin, p. 144, fig. 4E.

2009 ovoidal acritarch with striated ornamentation Peng et al., fig. 4.

2009 ovoidal acriatrch with striated ornamentation Lamb et al., fig. 4 A.

?2012 “dark walled megasphaeric coccoid with a subradial striation” Battison and Brasier, fig. 8B.

2015 Valeria lophostriata; Tang et al., p. 315, fig. 11.

in press Valeria lophostriata; Riedman and Porter, p. 10, fig. 4.1.

in press Valeria lophostriata; Porter and Riedman, fig. 19.1–19.3.

(For additional synonymy see Jankauskas et al., 1989, and Hofmann and Jackson, 1994)

Holotype.—Number 16-62-4762/16, sp. 1, DH Kabakovo 62 drill core, depth 4762 to 4765 meters, Neoproterozoic Zigazino-Komarovo Formation, southern Urals (Jankauskas, 1979b, fig. 1.14).

Description.—Large vesicle, 104–160 µm in minimum diameter, with lanceolate folds and a distinctive ornamentation of concentric ridges, giving the appearance of a “target” (Fig. 7.3, 7.4).

Occurrence.—This taxon is found worldwide (Hofmann, 1999) from the late Paleoproterozoic Era (Javaux et al., 2004; Lamb et al., 2009; Peng et al., 2009) to the Cryogenian (Nagy et al., 2009).

Materials.—Several specimens observed, mostly in samples U6 305.1 m, U6 273.7 m, and U6 240.2m from the Mainoru Formation.

Remarks.—SEM analyses show that the striations are 1-µm ridges located on the inside of the vesicle wall (Javaux et al., 2004). Excystment by medial split gives rise to two half vesicles that commonly enroll onto themselves (Fig. 7.1, 7.2).

Description.—A large ovoidal or irregular and globular envelope including several contiguous compartments, each surrounded by an envelope and containing closely packed spheroidal cells. Two fragmented specimens are 350 µm wide and 600–700 µm long, internal compartments surrounded by an inner envelope 39–85 µm in diameter, containing poorly defined, closely packed cells. The external envelope is 8–13 µm thick.

Materials.—Two specimens in sample U6 305.1m from the Mainoru Formation.

Description.—Black opaque vesicles, 141 and 215 µm in diameter (N = 2), with medial split and folds at periphery.

Materials.—Two specimens in sample GG1 340.2m from the Corcoran Formation.

Remarks.—These vesicles differ from Chuaria circularis by the translucent margin showing folds.

Description.—Vesicles with smooth to chagrinate walls, 30 and 35m in diameter (N = 2), connected by a 14-µm-long filamentous expansion.

Materials.—Two vesicles in sample U5 125.1m from the Jalboi Member.

Description.—Vesicle 40 µm in diameter, attached to a large 80 µm filamentous expansion, but not communicating with the cell interior (thus distinct from Germinosphaera).

Materials.—One specimen in sample GG1 326.2m from the Corcoran Formation.

Description.—Large, smooth-walled, thick, brittle, brownorange wall fragment of a spheromorph, 310 µm in diameter.

Materials.—One specimen in sample U6 240.2m from the Mainoru Formation.

Description.—Large, 16 to 29 µm wide filament in a 72 µm × 171 µm smooth indented sheath.

Materials.—A single specimen in sample U5 437m from the Mainoru Formation (Showell Creek Member).

Remarks.—This large filamentous fossil differs from other sheathed filamentous taxa by the indentation of the sheath and absence of septae in the filament, although these characters could be taphonomic. Other taxa, such as Rugosoopsis, can reach large diameters, but have a distinct transverse fabric not observed here. Palaeolyngbya may also have a wide sheath, but is characterized by regular uniseriate array of well-preserved cells (Butterfield et al., 1994).