Type species

Caelatimurus foveolatus Riedman and Porter, Reference Riedman and Porter2016, by monotypy.

Caelatimurus foveolatus Riedman and Porter, Reference Riedman and Porter2016

Figure 3.1

Figure 3 Caelatimurus foveolatus Riedman and Porter, Reference Riedman and Porter2016: (1, 1a) UCMP 36105a, SP14-63-8.

1978 Sphere with type I reticulate surface; Reference Pang, Tang, Schiffbauer, Yao, Yuan, Wan, Chen, Ou and XiaoPeat et al., p. 5, fig. 3A.

1978 Sphere with type II reticulate surface; Reference Pang, Tang, Schiffbauer, Yao, Yuan, Wan, Chen, Ou and XiaoPeat et al., p. 5, fig. 3B, D–F.

1984 Turuchanica maculata; Reference Tynni and UutelaTynni and Uutela, p. 24, ?fig. 175, fig. 176, non 177, nec 178–179, ?180–182, nec 183–186.

2016 Caelatimurus foveolatus Reference Riedman and PorterRiedman and Porter, p. 859, fig. 3.6–3.8.

Holotype

South Australian Museum Collection number P49508 (fig. 3.6–3.7), from sample 1265.57 m- slide19A, Giles 1 drill core, Neoproterozoic Alinya Formation, Officer Basin, Australia (Riedman and Porter, Reference Riedman and Porter2016).

Description

Organic-walled vesicle 29 µm in diameter with wall consisting of a raised network surrounding circular to elliptical depressions, 1.0 to 3.0 µm in maximum length and 1.0–1.5 µm in width. There are approximately 40 depressions per 100 µm² area of the vesicle surface.

Remarks

The type and all other reported specimens of this species are known only from light microscopy, making direct comparisons with the Chuar material difficult. (See Riedman and Porter, Reference Riedman and Porter2016, for a discussion of the species concept.) Nonetheless, the size, shape, distribution, and arrangement of the depressions in the wall of the Chuar specimen are indistinguishable from the ‘ellipsoidal depressions’ exhibited by other C. foveolatus specimens (Riedman and Porter, Reference Riedman and Porter2016), and the size of the Chuar vesicle falls within error of the range reported for the other material (~30–60 µm; Riedman and Porter, Reference Riedman and Porter2016). We therefore assign this specimen to C. foveolatus.

Genus Cerebrosphaera Butterfield in Butterfield, Knoll, and Swett, Reference Butterfield, Knoll and Swett1994

Type species

Cerebrosphaera globosa (Ogurtsova and Sergeev, Reference Ogurtsova and Sergeev1989) Sergeev and Schopf, Reference Sergeev and Schopf2010.

Diagnosis

As for type species by monotypy (emended from Butterfield et al., Reference Butterfield, Knoll and Swett1994).

Remarks

Butterfield et al. (Reference Butterfield, Knoll and Swett1994) provided separate diagnoses for the genus Cerebrosphaera and its single species, stating that the latter is characterized by vesicles 100-1,000 µm in diameter. We have produced a single diagnosis for the species and its monotypic genus, modifying the generic diagnosis given by Butterfield et al. (Reference Butterfield, Knoll and Swett1994) to include the vesicle sizes. We have also changed the stated vesicle wall thickness, formerly ~1.5 µm, to accommodate the new specimens studied here.

Cerebrosphaera globosa (Ogurtsova and Sergeev, Reference Ogurtsova and Sergeev1989) Sergeev and Schopf, Reference Sergeev and Schopf2010

Figure 4.1–4.9

Figure 4 Cerebrosphaera globosa (Ogurtsova and Sergeev, Reference Ogurtsova and Sergeev1989) Sergeev and Schopf, Reference Sergeev and Schopf2010. (1) Specimen showing marked variation in wrinkle widths, UCMP 36106a, SP14-63-08. (2) Fragment of vesicle with subparallel wrinkles, UCMP 36106b, SP14-63-08. (3) View of vesicle wall’s inner surface, UCMP 36105b, SP14-63-8. (4) UCMP 36106c, SP14-63-08. (5) Fragment of vesicle showing semielliptical shape of wrinkles, SP14-63-14. (6, 6a) UCMP 36086a, SP14-63-12. (6a) Note subtle pocked texture of vesicle surface, as well as partly degraded area of wall; location of image is indicated by box in (6). (7) Folded fragment showing thickness of vesicle wall, UCMP 36105c, SP14-63-8. (8, 9) Three-dimensional vesicles preserved in chert from the Lower Dolomite Member, Svanbergfjellet Formation, Krystalfjellet Peninsula, eastern Murchisonfjord, Svalbard, appear closely similar to specimens of C. globosa described by Ogurtsova and Sergeev (Reference Ogurtsova and Sergeev1989) and Sergeev and Schopf (Reference Sergeev and Schopf2010). (8, 8a) The same specimen at different focal planes, sample G155.100.6 TS5. (9) Sample G155.100.6 TS4.

1983 Unnamed Form B of Knoll (1983); Reference Knoll and CalderKnoll and Calder, pl. 60, fig. 6.

1984 Unnamed Form B; Reference KnollKnoll, p. 160, fig. 9D–F.

1989 Chuaria globosa Reference Ogurtsova and SergeevOgurtsova and Sergeev, p. 121, fig. 1а, г, з.

1991 Leiosphaeridia sp. cf. L. atava; Reference Knoll, Swett and MarkKnoll et al., p. 558, fig. 21.2, 21.3.

1992b Stictosphaeridium sinapticuliferum; Reference Zang and WalterZang and Walter, p. 311, pl. 8K.

1994 Cerebrosphaera buickii Butterfield; Reference Butterfield, Knoll and SwettButterfield et al., p. 30, fig. 12.

1999 Cerebrosphaera buickii; Reference CotterCotter, p. 70, fig. 6D, F–H.

1999 Cerebrosphaera ananguae Reference CotterCotter, p. 69, fig. 6A, B, E.

2000 Cerebrosphaera buickii; Reference Hill, Cotter and GreyHill et al., fig. 7.

2006 ?Cerebrosphaera globosa; Reference SergeevSergeev, pl. 48, figs. 8–10, ?11–?13.

2009 Cerebrosphaera buickii; Reference Nagy, Porter, Dehler and ShenNagy et al., fig. 1K.

2010 ?Cerebrosphaera globosa; Reference Sergeev and SchopfSergeev and Schopf, p. 394, fig. 13.5, 13.5A, 13.8.

2011 Cerebrosphaera buickii; Reference Grey, Hill and CalverGrey et al., fig. 8.6A–I.

Holotype

ИГ АН Киргизской ССР, thin section ЧК 1-83, No. 1. Neoproterozoic Chichkan Formation, Shabakty, Maly Karatau Range, Kazakhstan (Ogurtsova and Sergeev, Reference Ogurtsova and Sergeev1989, fig. 1a).

Diagnosis

Spheroidal vesicles typically 100 to 1,000 µm in diameter with regularly and prominently wrinkled walls. Wrinkles sinuous: anastomosing, interfingering, or rarely, subparallel, but never intersecting. Vesicle walls ~1.0 to 1.5 µm thick, inelastic, and often opaque. Outer, thin-walled envelope sometimes present (emended from Sergeev and Schopf, Reference Sergeev and Schopf2010; adapted from Butterfield et al., Reference Butterfield, Knoll and Swett1994).

Occurrence

Tanner, Carbon Canyon, and Duppa members, Chuar Group; widespread in other late Tonian units including the Chichkan Formation, southern Kazakhstan (Ogurtsova and Sergeev, Reference Ogurtsova and Sergeev1989; Sergeev and Schopf, Reference Sergeev and Schopf2010); Svanbergfjellet and Draken formations, Akademikerbreen Group, Svalbard (Knoll et al., Reference Knoll, Swett and Mark1991; Butterfield et al., Reference Butterfield, Knoll and Swett1994); Ryssö Formation, Murchisonfjorden Supergroup, Svalbard (Knoll and Calder, Reference Knoll and Calder1983); Gouhou Formation, Huaibei Group, China (Zang and Walter, Reference Zang and Walter1992b); Hussar and Kanpa formations (Empress 1A, Hussar 1, Lungkarta 1, and Lancer 1 drill cores), Pirrilyungka Formation (Vines 1 drill core), and Kanpa Formation (Yowalga 2 drill core), Officer Basin, Western Australia (Cotter, Reference Cotter1999; Hill et al., Reference Hill, Cotter and Grey2000; Grey et al., Reference Grey, Hill and Calver2011); Skillogalee Dolomite (BLD 4 drill core), and Anama Siltstone Member, Rhynie Sandstone, Burra Group (PP12 drill core), Stuart Shelf, South Australia (Hill et al., Reference Hill, Cotter and Grey2000; Grey et al., Reference Grey, Hill and Calver2011); ‘Finke beds,’ Amadeus Basin, Australia (Grey et al., Reference Grey, Hill and Calver2011).

Description

Spheroidal vesicles 160 to 375 µm in diameter (mean=242 µm, SD=70 µm, N=17), with complexly wrinkled walls. Wrinkles sinuous and may occur singly or may anastomose. Wrinkles vary in width within individual specimens from >4 µm thick to barely visible, reflecting the degree to which the wall is folded on itself (Fig. 4.1, 4.4). Wrinkle widths also vary along the length of a single wrinkle, with some wrinkles forming semi-elliptical shapes, tapering off at both ends (Fig. 4.5). Wrinkles vary in width among specimens from 1.5 to 5.5 µm (N=19; based on measurements of the narrowest wrinkles in each specimen). Wrinkle orientations may vary within and between vesicles, with neighboring wrinkles subperpendicular (Fig. 4.5, 4.6) to subparallel (Fig. 4.2, 4.4). On the outer surface of the vesicle, wrinkles take the form of ridges separated by U-shaped valleys. On the internal surface of the vesicle, wrinkles take the form of narrow, sinuous valleys separated by raised, smoothly rounded, sinuous hills (Fig. 4.3), giving the surface an appearance similar to cerebral convolutions of the human brain.

Vesicle wall is 1.0 to 1.2 µm thick (N=2; Fig. 4.7) and exhibits a subtle pocked texture (Fig. 4.6, 4.6a; cf. the ‘psilate to slightly granular’ wall of Cotter, Reference Cotter1999), likely taphonomic in origin (Grey and Willman, Reference Grey and Willman2009).

Remarks

Following the suggestion of Sergeev (Reference Sergeev2006), Sergeev and Schopf (Reference Sergeev and Schopf2010) transferred Chuaria globosa Ogurtsova and Sergeev, Reference Ogurtsova and Sergeev1989 with question to Cerebrosphaera. Although the description and images of ?C. globosa specimens suggest they are closely comparable to the type material of C. buickii (also see the discussion of Butterfield et al., Reference Butterfield, Knoll and Swett1994), Sergeev and Schopf (Reference Sergeev and Schopf2010) left them in a separate species because their different mode of preservation made it difficult to compare them in detail (three-dimensional vesicles in chert vs. the flattened carbonaceous disks illustrated in Butterfield et al., Reference Butterfield, Knoll and Swett1994). Newly discovered specimens from the Svanbergfjellet Formation preserved three dimensionally in chert (Fig. 4.8, 4.9) are closely similar to those illustrated from the Chichkan Formation; indeed, we see no obvious basis for distinguishing these two populations. We therefore formally synonymize these two species. Because C. globosa was erected first (by Ogurtsova and Sergeev, Reference Ogurtsova and Sergeev1989), that specific epithet has priority. We agree with Sergeev (Reference Sergeev2006) and Sergeev and Schopf (Reference Sergeev and Schopf2010) that this species is sufficiently different from the type species of Chuaria, C. circularis, both in terms of its size and its characteristic wrinkling, that it should be removed from that genus. We place it here, without question, in Cerebrosphaera Butterfield in Butterfield et al., Reference Butterfield, Knoll and Swett1994.

Cotter (Reference Cotter1999) erected a new species of Cerebrosphaera, C. ananguae, that she distinguished from C. buickii on the basis of its looser pattern of wrinkles and its greater wall thickness (>2 µm), the latter inferred by measuring the average width of the narrowest wrinkles and dividing by two. Wrinkle thicknesses in the Chuar specimens spanned the thicknesses cited for C. buickii and C. ananguae in Cotter (Reference Cotter1999) and we found no clear breaks in this distribution, nor did we find obvious clustering related to the wrinkle spacing (i.e., loosely vs. tightly spaced wrinkles). Furthermore, in the Chuar specimens, there does not appear to be a correlation between wall thickness and the width of the narrowest wrinkles, at least for the two specimens in which wall thickness could be ascertained (e.g., Fig. 4.7). Indeed, the fact that wrinkles vary rather widely in thickness, spacing, and relative orientation both within and among specimens suggests that the variation in these characteristics is likely related to differences in postmortem shrinkage and/or compaction. (The distinctive pattern of the wrinkling itself, however, a pattern that is visible even in strongly flattened specimens [Fig. 4.1, 4.6] and in three-dimensionally preserved specimens [Fig. 4.8, 4.9], suggests that the wrinkles reflect the biological character of wall composition.) Because of the continuous variation in wrinkle thickness and spacing, and because this variation likely reflects taphonomic differences, we regard C. ananguae as a junior synonym of C. globosa. We also revise the diagnosis for C. globosa, replacing it with a diagnosis modified from that given by Butterfield et al. (Reference Butterfield, Knoll and Swett1994) for the genus Cerebrosphaera.

One of three specimens described as Stictosphaeridium sinapticuliferum Timofeev by Zang and Walter (Reference Zang and Walter1992b: pl. 8, fig. K) is interpreted here to be C. globosa. This specimen comes from the Gouhou Formation, Huaibei Group, at the Gouhou section, Suxian County, Huaibei Province, China. Other fossils reported from the Gouhou Formation (e.g., Chuaria, Tawuia, Trachyhystrichosphaera aimika Hermann in Timofeev et al. Reference Timofeev, Hermann and Mikhailova1976, emend. Butterfield et al., Reference Butterfield, Knoll and Swett1994, and Valeria lophostriata [Jankauskas, Reference Jankauskas1979b] Jankauskas, Reference Jankauskas1982) indicate a late Tonian age (Tang et al., Reference Tang, Pang, Yuan, Wan and Xiao2015).

Genus Culcitulisphaera Riedman and Porter, Reference Riedman and Porter2016

Type species

Culcitulisphaera revelata Riedman and Porter, Reference Riedman and Porter2016, by monotypy.

Culcitulisphaera revelata Riedman and Porter, Reference Riedman and Porter2016

Figure 5.1–5.7

Figure 5 Culcitulisphaera revelata Riedman and Porter, Reference Riedman and Porter2016. (1–3) Three specimens showing variation in preservation of pillows, with increasing deflation from left to right. (1, 1a) UCMP 36104a, SP14-63-29; (2, 2a) UCMP 36091a, SP14-63-14; (3, 3a) UCMP 36073a, SP12-63-30. (4–5) Two specimens, each with outer layer missing, revealing spongy structure beneath. (4, 4a) UCMP 36093a, SP14-63-14; (5, 5a, 5b) UCMP 36080a, SP14-63-11. (6) TLM image of vesicle showing lighter spots where pillows occur (also see 5a), UCMP 36088a, SP14-63-14. (7) Vesicle with envelope preserved; crack in the envelope (indicated by arrow) reveals the smooth outer layer of the vesicle wall underneath; UCMP 36092a, SP14-63-14. Scale bar in (5) also for (5a).

1979 Kildinella sp.; Reference VidalVidal, pl. 4, figs. C–D.

?1985 Trachysphaeridium sp. A; Reference Vidal and FordVidal and Ford, p. 377, fig. 8B, D.

1992 Trachysphaeridium laminaritum; Reference SchopfSchopf, pl. 14, fig. A

2009 Trachysphaeridium laminaritum; Reference Nagy, Porter, Dehler and ShenNagy et al., fig. 1H.

2016 Culcitulisphaera revelata Reference Riedman and PorterRiedman and Porter, p. 861, figs. 5, 6.4–6.6, 7, 8.

Holotype

South Australian Museum Collection number P49519, sample 1265.56 m- slide 19A, Giles 1 drill core, Neoproterozoic Alinya Formation, Officer Basin, Australia (Riedman and Porter, Reference Riedman and Porter2016, fig. 5.1).

Diagnosis

Optically dense sphaeromorphic organic-walled microfossil distinguished by a surface ornament of tightly packed 1- to 3-µm cushion-shaped outpockets of the vesicle that may appear only as ~1-µm diameter light spots or alveolae under light microscopy (from Riedman and Porter, Reference Riedman and Porter2016).

Occurrence

Tanner, Jupiter, Carbon Canyon, and Duppa members, Chuar Group; also occurs in the Neoproterozoic Alinya Formation in the Giles 1 drill core, Officer Basin, Australia (Riedman and Porter, Reference Riedman and Porter2016); in bed 19, of the late Tonian Limestone-Dolomite Series, Eleonore Bay Group, Greenland (Vidal, Reference Vidal1979); and in the latest Mesoproterozoic–earliest Neoproterozoic Lakhanda Group, Khabarovsk region, Siberia (Schopf, Reference Schopf1992). Possible occurrence in the late Tonian Uinta Mountain Group, Utah (Vidal and Ford, Reference Vidal and Ford1985).

Description

Organic-walled vesicles 24 to 127 µm in diameter (mean=48 µm, SD=26, N=15) with an outer layer that formed pillow-like outpocketings 1 to 2 µm in diameter (mean=1.5 µm, SD=0.2 µm, N=27). These may appear deflated (Fig. 5.1, 5.2) or sunken into the surface of the vesicle (Fig. 5.3). In the latter, the vesicle surface has a honeycomb-like appearance, which we interpret as reflecting a mechanically resistant structure that subtended the outer layer and supported the pillows. In some specimens, the outer layer is missing, revealing a complex, spongy material that forms the honeycomb-like structure that supports the pillows (Fig. 5.4, 5.5; see reconstruction of the wall in Fig. 25). Under transmitted light microscopy, the pillows appear as spots that are less optically dense than their surroundings (Fig. 5.5a, 5.6). This likely reflects the fact that the spongy material is thinner in these areas.

A few specimens are covered by a thin, smooth wall that is cracked in places to reveal a smooth, honeycomb-like surface underneath—not the spongy material of the inner vesicle layer (Fig. 5.7). This is interpreted to represent an envelope that covered the outer, pillow-forming layer of the vesicle wall (Fig. 25). No specimens exhibit evidence for excystment structures.

Remarks

Riedman and Porter (Reference Riedman and Porter2016) provide a thorough discussion of C. revelata and its species concept. The Chuar assemblage closely resembles that described by Riedman and Porter (Reference Riedman and Porter2016) in the Alinya Formation, Giles 1 drill core, Australia. Particularly noteworthy is the frequent presence of 30- to 600-nm nanopores in the walls of specimens from the Alinya Formation, revealed during serial sectioning via FIB-SEM (Riedman and Porter, Reference Riedman and Porter2016). Their size, position, and distribution make it likely that these are spaces in the spongy network visible in some Chuar specimens (e.g., Fig. 5.5).

Genus Galerosphaera new genus

Type species

Galerosphaera walcottii Vidal and Ford, Reference Vidal and Ford1985 n. comb., by monotypy.

Diagnosis

As for type species by monotypy.

Etymology

From the Galeros Formation, the lower, acritarch-rich unit of the Chuar Group, and the Latin sphaera, meaning sphere.

Remarks

Vidal and Ford (Reference Vidal and Ford1985) were the first to describe specimens of G. walcottii and placed the species in the genus Vandalosphaeridium Vidal (Reference Vidal1981). Although the diagnosis of Vandalosphaeridium is broad enough to permit the inclusion of G. walcottii, this species is quite distinct from the type species of Vandalosphaeridium, V. reticulatum (=Peteinosphaeridium reticulatum Vidal [Reference Vidal1976b], misspelled as Pteinosphaeridium reticulatum in that same paper). In V. reticulatum the processes furcate distally to form polygonal (“net-like”: Vidal, Reference Vidal1976b, p. 27 and fig. 14A–K) compartments, whereas in G. walcottii the processes expand distally but do not connect with one another. Given the differences in the shape and topology of their processes, we see no convincing reason to think that G. walcottii and V. reticulatum have a close biological relationship, and thus we remove G. walcottii from Vandalosphaeridium. By contrast, the other species in Vandalosphaeridium, V. koksuicum Sergeev and Schopf, Reference Sergeev and Schopf2010 and V. varangeri Vidal, Reference Vidal1981, appear to exhibit the same polygonal compartments observed in V. reticulatum, supporting their inclusion in Vandalosphaeridium.

Among extant protists, cysts with funnel-like processes are known in dinoflagellates, green algae, and ciliates (Foissner et al., Reference Foissner, Müller and Agatha2007; Moczydłowska, Reference Moczydłowska2010). Thus this character has apparently evolved several times independently and is not likely to be useful by itself in establishing taxonomic relationships.

Galerosphaera walcottii (Vidal and Ford, Reference Vidal and Ford1985) new combination

Figure 6.1–6.8

Figure 6 Galerosphaera walcottii (Vidal and Ford, Reference Vidal and Ford1985) n. comb. (1, 1a) UCMP 36080b, SP14-63-11. (2) UCMP 36083a, SP14-63-11. (3, 3a) UCMP 36088b, SP14-63-14. (4) SP14-63-11. (5, 5a) Note flaring of process tip to form funnel-like structure, UCMP 36092b, SP14-63-14. (6) SP14-63-11. (7, 7a) UCMP 36080c, SP14-63-11. (8) Arrow points to hair-like structures on vesicle surface; SP12-69-14.

1985 Vandalosphaeridium walcottii Reference Vidal and FordVidal and Ford, p. 376, fig. 8E, F.

2009 Vandalosphaeridium walcottii; Reference Nagy, Porter, Dehler and ShenNagy et al., fig. 1G.

Holotype

LO 5661, slide GC-80-13:2-A, Collections of the Department of Historical Geology and Palaeontology, University of Lund; late Tonian Awatubi Member, Kwagunt Formation, Chuar Group (Vidal and Ford, Reference Vidal and Ford1985: fig. 8E). (The holotype entry states Walcott Member, but elsewhere in the text the sample is referred to the Awatubi Member.) Eastern Grand Canyon, Arizona. Specific locality information not provided.

Diagnosis

Spheroidal vesicle covered by evenly scattered, widely spaced, short, sturdy processes with funnel-like distal portions that support an external translucent and smooth envelope completely enclosing the vesicle (emended from Vidal and Ford, Reference Vidal and Ford1985).

Occurrence

Tanner Member; Vidal and Ford (Reference Vidal and Ford1985) also report G. walcottii from the Awatubi Member (their reported occurrence in the Walcott Member is apparently erroneous; see the preceding).

Description

Organic-walled microfossils 35 to 51 µm in maximum diameter (mean=40 µm, SD=5 µm, N=7), with processes 2 to 5 µm in length that connect to an outer envelope (=‘membrane; of Vidal and Ford, Reference Vidal and Ford1985). Processes are ~1 µm in width proximally but flare at their distal end to form funnel-like structures ~2 µm in maximum width (Fig. 6.5a). Funnel-like distal portions appear to be wider in one dimension than the other (i.e., they appear flattened; Figs. 6.5, 6.6, 25), but it is possible this reflects compaction. Processes are more or less evenly and widely spaced, with ~10 per 100 µm² area. The outer envelope is translucent under light microscopy and exhibits both ductile deformation (folding over the underlying processes) and brittle deformation. One specimen exhibits short (<<1 µm) fine hair-like structures arising from the surface of the vesicle between the processes (Fig. 6.8, black arrow).

Basionym

Vandalosphaeridium walcottii Vidal and Ford, Reference Vidal and Ford1985 (p. 376–377.)

Remarks

Vidal and Ford’s (Reference Vidal and Ford1985) diagnosis is emended here so that reference to a rigid (as opposed to flexible) outer envelope has been removed as specimens studied here do not show evidence for rigidity. We have been unable to determine whether the processes are hollow.

Genus Kaibabia new genus

Type species

Kaibabia gemmulella n. gen. n. sp., by monotypy

Diagnosis

As for type species by monotypy.

Etymology

Named for the Kaibab Tribe of the southern Paiute, whose traditional lands include the north rim of the Grand Canyon.

Remarks

Vidal and Ford (Reference Vidal and Ford1985) assigned similar specimens from the Chuar Group to Leiosphaeridia Eisenack, Reference Eisenack1958b, comparing them to L. asperata (Naumova, Reference Naumova1950) Lindgren, Reference Lindgren1982 but leaving them in open nomenclature. However, Leiosphaeridia is a form genus comprising species that themselves are form taxa and that are characterized by a lack of ornament or sculpture (Jankauskas et al., Reference Jankauskas, Mikhailova and Hermann1989). By contrast, the distinctive granulate operculum that is diagnostic of K. gemmulella contradicts its placement in the smooth-walled Leiosphaeridia and suggests it is a real biological taxon. Because of this distinctive and unique feature, we here erect the new genus Kaibabia for this new species.

Kaibabia gemmulella new species

Figure 7.1–7.9

Figure 7 Kaibabia gemmulella. n. gen. n. sp. (1, 1a) Holotype, UCMP 36082a, SP14-63-11. (2) Specimen in which operculum is partially detached, revealing a hole in the wall, SP14-63-11. (3, 3a) Specimen with relatively small operculum and few granulae, UCMP 36093b, SP14-63-14. (4) Specimen with circular hole in the wall, similar to that in (2), likely where operculum once was, UCMP 36099a, SP14-63-23. (5, 5a) Specimen with outer envelope preserved, showing impressions of opercular granulae beneath, UCMP 36091b, SP14-63-14. (6) TLM image showing partly detached operculum (arrow), UCMP 36083b, SP14-63-11. (7) Specimen with possible processes (black arrows) and thin outer envelope (visible on left side). Operculum indicated by white arrow, UCMP 36083c, SP14-63-11. (8, 8a, 8b) UCMP 36098, SP14-63-23. (8a, 8b) Closeup images of operculum showing numerous ~1 µm diameter granulae. (9) UCMP 36076, SP12-63-8.

?1980 Leiosphaeridia kulgunica Reference JankauskasJankauskas, p. 192, fig. 1.1–1.4.

1985 Leiosphaeridia sp. A; Reference Vidal and FordVidal and Ford, p. 364, figs. 4B, 4D, 7C.

?1989 Leiosphaeridia kulgunica; Reference Jankauskas, Mikhailova and HermannJankauskas et al., p. 78, pl. 11, 8–10.

?1992 Leiosphaeridia kulgunica; Reference SchopfSchopf, pl. 19G.

2009 Leiosphaeridia sp. A; Reference Nagy, Porter, Dehler and ShenNagy et al., fig. 1C.

Holotype

UCMP 36082a, SP14-63-11, SEM slide ker-5, EF=A39, Lava Chuar Canyon locality, Tanner Member, Galeros Formation, Chuar Group, Grand Canyon (Fig. 7.1).

Diagnosis

Originally spheroidal, smooth, organic-walled microfossils with elliptical to circular operculum; outer surface of operculum covered in numerous ~1-µm-diameter granulae. Operculum may be absent, leaving a well-defined circular hole. Outer envelope may be present.

Occurrence

Tanner, Jupiter, Carbon Canyon, and Duppa members. Vidal and Ford (Reference Vidal and Ford1985) also reported the species from the Awatubi Member.

Description

Smooth-walled vesicles 30 to 67 µm in diameter (mean=42 µm, SD=11 µm, N=14), with circular to elliptical operculum; outer surface of operculum covered in ~1-µm-diameter hemispherical granulae. Opercula are 6 to 13 µm in diameter (long axis; mean=9 µm, SD=2 µm, N=14), and bear on their surface between 10 and 40 granulae. Operculum diameter positively correlated with both the number of granulae (Pearson’s correlation coefficient, r=0.7, R²=0.5) and the diameter of the vesicle (r=0.8, R²=0.7) (Fig. 8). Granulae vary more widely in diameter within a single operculum in specimens with higher numbers of granulae. In some specimens, the operculum is partly detached (Fig. 7.2) or missing (Fig. 7.4) revealing a circular hole with a smooth margin. Outer envelope, when present, exhibits impressions of granulae underneath (Fig. 7.5). One specimen exhibits several structures that may be short (~1 µm) processes (Fig. 7.7).

Figure 8 Relationship of the diameter of the operculum in Kaibabia gemmulella to the diameter of the vesicle (filled circles) and to number of granulae on the operculum (crosses). Both pairs of variables are positively correlated, indicating that larger opercula are associated both with larger vesicles and with higher numbers of granulae.

Etymology

Double diminutive form of the Latin gemma, meaning jewel.

Remarks

The consistent sizes of the granulae (~1 µm) together with continuous variation in vesicle and operculum size (Fig. 8) suggests that the specimens examined here are part of the same species. The presence of an outer envelope—likely representing the vegetative cell wall—suggests the vesicle itself was a cyst, consistent with the presence of an operculum. (Note that, by itself, the presence of an operculum does not imply the vesicle is a cyst as some vegetative cells also possess opercula [Moczydłowska, Reference Moczydłowska2010]).

Vidal and Ford (Reference Vidal and Ford1985) noted similarities between Kaibabia gemmulella (=Leiosphaerida sp. A) and Leiosphaeridia asperata (Naumova, Reference Naumova1950) Lindgren, Reference Lindgren1982, but regarded K. gemmulella as most likely representing a different species on the basis of its distinctive operculum. They suggested the operculum was similar to the protuberances exhibited by some specimens of Lanulatisphaera laufeldii (Vidal, Reference Vidal1976b) n. comb. (=Trachysphaeridium laufeldi, see illustrations under the species), but the similarity is superficial. We agree that the operculum of K. gemmulella can be used as a diagnostic character and herein formalize the assignment of K. gemmulella to a distinct taxon.

Vidal and Ford (Reference Vidal and Ford1985) compared K. gemmulella (=Leiosphaeridia sp. A) to Leiosphaeridia kulgunica Jankauskas, Reference Jankauskas1980, described from the upper Riphean (Tonian) Shisheniak microbiota of the South Urals (see also Jankauskas et al., Reference Jankauskas, Mikhailova and Hermann1989; Schopf, Reference Schopf1992, in which the same specimens are illustrated). The holotype of L. kulgunica also has a circular hole in the vesicle wall, presumably where an operculum once was. Both the diameter of its vesicle (~30 µm) and that of the hole (~9 µm) fall within the range of sizes exhibited by K. gemmulella, and it appears similar to specimens of K. gemmulella in which the operculum is missing (e.g., Fig. 7.4). Other specimens in the Shisheniak assemblage, however, fall significantly outside the size range for K. gemmulella (Jankauskas, Reference Jankauskas1980, fig. 1.4). It is possible that K. gemmulella is conspecific with L. kulgunica, but the absence of an operculum in the latter makes this difficult to assess.

Genus Lanulatisphaera new genus

Type species

Lanulatisphaera laufeldii (Vidal, Reference Vidal1976b) n. comb., by monotypy.

Diagnosis

As for type species.

Etymology

From the Latin lanulata, a diminutive for ‘woolly,’ referring to the dense, matted appearance of the filaments between the vesicles; and sphaera in reference to the shape of the whole of the fossil.

Remarks

New morphological data require the placement of ‘Trachysphaeridium’ laufeldii into a new genus. The original description of Trachysphaeridium (Timofeev, Reference Timofeev1959) lacked a diagnosis but was described as “thick, dense vesicle with shagreen surface” (translated from Timofeev, Reference Timofeev1959, p. 28) and as “single-layered sphaerical vesicles 60 to 250 µm in diameter of varying thickness and density with shagreen surface that is usually compressed into folds” (translated from Timofeev, Reference Timofeev1966, p. 36). The genus Trachysphaeridium was synonymized with Leiosphaeridia by Jankauskas et al., (Reference Jankauskas, Mikhailova and Hermann1989) because features Timofeev used to distinguish these two genera, such as folding and a rough-textured vesicle, were considered to be taphonomically induced. This is likely to be the correct placement for some species of Trachysphaeridium, including the type species, T. attenuatum. However, forms attributed to T. laufeldii possess morphological features inconsistent with a placement in Leiosphaeridia, a form genus of smooth-walled sphaeroids. Samuelsson (Reference Samuelsson1997) interpreted the processes of this species to be tubercles upon the vesicle and transferred it to Lophosphaeridium Timofeev, Reference Timofeev1959 ex Downie, Reference Downie1963, a genus diagnosed by a thick vesicle with a knobby, tuberculate surface sculpture. That transfer is rejected here as a tuberculate sculpture has not been borne out by SEM study. Because no existing genus is known that can accommodate the features diagnostic of this species, a new genus and combination is established here.

Lanulatisphaera laufeldii (Vidal, Reference Vidal1976b) new combination

Figures 9.1–9.6, 10.1–10.7, 11.1–11.4, 12.1–12.7, ?12.8

Figure 9 Lanulatisphaera laufeldii (Vidal and Ford, Reference Vidal and Ford1985) n. comb., showing possible ontogenetic or ecophenotypic series, from (1, 1a) individual fibers to (2, 2a) cones formed from coalesced fibers, to (3, 3a, 4, 4a) a mix of cones and anastomosing network, to (5, 5a) network only, to (6, 6a) a higher order arrangement of the network. (1, 1a) UCMP 36090a, SP14-63-14. (2, 2a) UCMP 36085a, SP14-63-12_010. (3, 3a) UCMP 36073b, SP12-63-30. (4, 4a) Specimen also shown using TLM in Fig. 12.5; UCMP 36072a, SP12-63-30. (5, 5a) UCMP 36073c, SP12-63-30. (6, 6a) UCMP 36073d, SP12-63-30.

Figure 10 Lanulatisphaera laufeldii (Vidal and Ford, Reference Vidal and Ford1985) n. comb. (1, 1a) Torn specimen showing that the vesicle’s interior surface is smooth and that the fibers are outgrowths of the vesicle wall (black arrow in 1a), UCMP 36073f, SP12-63-30. (2, 2a) Specimen with rounded protuberance (white arrow in 2) UCMP 36099b, SP14-63-23. (3) Specimen with circular opening (white arrow) in its outer envelope (only a fragment of the envelope is preserved), UCMP 36086b, SP14-63-12. (4) Bright field TEM image of vesicle wall and envelope in cross section. Envelope clearly visible on right; white arrow points to possible mamilla in cross section; UCMP 36087b, SP14-63-14. (5, 5a) Specimen showing nano-scale mammillae on the outer surface of the envelope, UCMP 36090b, SP14-63-14. (6, 6a) Specimen showing (6) furrows as well as (6a) mammillae, UCMP 36087a, SP14-63-14. (7, 7a) specimen showing (7) furrows and (7a) ~2-µm-diameter disc (black arrow), UCMP 36079a, SP14-63-11.

Figure 11 Lanulatisphaera laufeldii (Vidal and Ford, Reference Vidal and Ford1985) n. comb. (1, 1a) Specimen with compressed network of fibers, UCMP 36073g, SP12-63-30. (2, 2a) Specimen with outer envelope preserved, showing network with fused fibers, likely reflecting taphonomic processes, UCMP 36073h, SP12-63-30. (3) Specimen with complete outer envelope (closeup images of holes in the outer envelope, not shown, reveal the presence of fibers beneath, confirming its assignment to L. laufeldii); UCMP 36073e, SP12-63-30. (4) Specimen showing possible opercula consisting of multiple rounded granulae, similar to the opercula of Kaibabia gemmulella, UCMP 36096a, SP14-63-17.

Figure 12 (1–7) Lanulatisphaera laufeldii (Vidal and Ford, Reference Vidal and Ford1985) n. comb. and (8) ?L. laufeldii. (1) Specimen with cones, UCMP 36083d, SP14-63-11. (2, 2a, 2b, 4, 4a, 4b) Specimens with mottled alveolar appearance similar to Trachysphaeridium laminaritum sensu Vidal (Reference Vidal1976b) and Vidal and Ford (Reference Vidal and Ford1985) that exhibit anastomosing filamentous processes (2a, 2b, 4a, 4b; note fused network visible beneath the envelope). (2, 2a, 2b) UCMP 36102, SP14-63-11. (4, 4a, 4b) UCMP 36082b, SP14-63-11. (3) Specimen with fibrous network visible on vesicle perimeter, UCMP 36083j, SP14-63-11. (5) Specimen with irregular textured appearance; SEM image of the same specimen illustrated in Figure 9.4, UCMP 36072b, SP12-63-30. (6, 6a, 6b, 7, 7a) Specimens with alveolar appearance similar to T. laminaritum sensu Vidal (Reference Vidal1976b) and Vidal and Ford (Reference Vidal and Ford1985), with outer envelopes similar to those of confirmed specimens of L. laufeldii (6a, 7a). (6, 6a, 6b) UCMP 36080e, SP14-63-11. (7, 7a) UCMP 36089b, SP14-63-14. (8, 8a) ?L. laufeldii specimens similar to those described as cf. Cymatiosphaeroides kullingii by Vidal and Ford (Reference Vidal and Ford1985), UCMP 36074a, SP12-63-30.

?1976a Trachysphaeridium laufeldi; Reference VidalVidal, fig. 2A.

1976b Trachysphaeridium laminaritum; Reference VidalVidal, p. 35, fig. 20A–B, F–H.

1976b Trachysphaeridium laufeldi Reference VidalVidal, p. 36, fig. 21A–N.

?1985 cf. Cymatiosphaeroides kullingii; Reference Vidal and FordVidal and Ford, p. 359, fig. 3B.

1985 Trachysphaeridium laufeldi; Reference Vidal and FordVidal and Ford, p. 375, fig. 7A, B.

?1985 Trachysphaeridium laufeldi; Reference Vidal and FordVidal and Ford, p. 375, fig. 7D, F.

1985 Trachysphaeridium laminaritum; Reference Vidal and FordVidal and Ford, p. 373, fig. 8A, C.

1996 Trachysphaeridium laminaritum; Reference KnollKnoll, pl. 4, fig. 6.

1997 Lophosphaeridium laufeldii; Reference SamuelssonSamuelsson, p. 174, fig. 7 F, H, I.

2009 Lophosphaeridium laufeldi; Reference Nagy, Porter, Dehler and ShenNagy et al., fig. 1J.

?2009 ?Kildinosphaera verrucata; Reference Nagy, Porter, Dehler and ShenNagy et al., fig. 1F.

2016 Lanulatisphaera laufeldii; Reference Riedman and PorterRiedman and Porter, p. 866, figs. 6.1–6.3, 9.9–9.12, 10.

Holotype

BV/83.60—1:X/53.3, middle member of the Neoproterozoic Visingsö Group, 83.6 m depth in the Kumlaby borehole, Visingsö Island, Sweden (Vidal, Reference Vidal1976b: fig. 21A-E).

Diagnosis

Double-walled, originally spheroidal, organic-walled microfossil bearing abundant submicron-diameter solid filamentous processes that arise from the exterior of the inner vesicle and fuse distally forming cone-like structures ~1 to 3 µm long or fuse and branch forming complex networks. Outer envelope bearing ~50 to 100 nm diameter mammillae; filamentous processes appear to make no contact with outer envelope (emended from Vidal, Reference Vidal1976b.)

Occurrence

Tanner, Jupiter, Carbon Canyon, Duppa, and Awatubi members of the Chuar Group and a possible occurrence in the Walcott Member; also occurs in other Tonian units including the Alinya Formation, Giles 1 drill core, Officer Basin, Australia (Riedman and Porter, Reference Riedman and Porter2016); Visingsö Group, Sweden (Vidal, Reference Vidal1976b); the Karuyarvinskaya Formation, Kildinskaya Group, Kola Peninsula, Russia (Samuelsson, Reference Samuelsson1997); and the Mount Watson and Red Pine Shale, Uinta Mountain Group (Vidal and Ford, Reference Vidal and Ford1985; unpublished data, Porter, 2014). Reported but not illustrated from the late Tonian Vadsø and Tanafjorden groups, East Finnmark, Norway (Vidal, Reference Vidal1981); and the Ryssö Formation, Nordaustlandet, Svalbard (Knoll and Calder, Reference Knoll and Calder1983). Possible occurrence in the Neoproterozoic Eleonore Bay Group (Vidal, Reference Vidal1976a).

Description

Organic-walled vesicles 24 to 84 µm in diameter (mean=42 µm, SD=10 µm, N=79), with walls ~0.5 µm thick. Electron density of walls homogeneous in cross section (Fig. 10.4). Inner surface of wall smooth (Fig. 10.1). Continuous with, and arising from (Fig. 10.1), the outer surface of the vesicle are moderately to densely packed solid fibers, ~0.2 to 0.4 µm in diameter. In some specimens, the fibers coalesce to form cone-like structures 0.5 to 2.9 µm high (mean=1.4 µm, SD=0.6 µm, N=20) and up to 2 µm wide at their base, with a tapered tip comparable in diameter to a single fiber (Fig. 9.2). In other specimens, the fibers both coalesce and branch, forming a network (Fig. 9.5) in which the fibers may appear to be more or less densely woven or even fused (Fig. 11.1, 11.2), the latter state likely reflecting taphonomic alteration. Some specimens exhibit an intermediate state, with both the network and cone-like structures visible (Fig. 9.3, 9.4). The network may form higher-order structures consisting of hollow spaces ~2 to 4 µm wide, separated by thin walls formed of the fiber network (Fig. 9.6), although whether this is original or reflects taphonomic processes is not clear (see the following). One specimen exhibits a rounded protuberance ~15 µm in diameter, also covered in fibers, and extending ~7 µm out from the wall (Fig. 10.2; cf. the “bulbous spiny protuberance” of Vidal and Ford, Reference Vidal and Ford1985, p. 375, fig. 7D–H; see also Vidal, Reference Vidal1976b, fig. 21A–N).

Several specimens exhibit a system of furrows in the network or the cones (Fig. 10.6, 10.7). Furrows are ~1 µm wide, straight or slightly sinuous, and often occur in parallel sets, with different sets at angles to each other. The furrows appear to be carved into the vesicle ornamentation and occur both in specimens with a network of filaments (Fig. 10.6) and in those with cone-like structures (Fig. 10.7). These furrows appear similar to the higher-order structures mentioned previously (Fig. 9.6) but differ in that the hollow spaces are rounded or polygonal rather than sets of straight parallel channels. Nonetheless, these features may be related, although it is not clear whether they represent taphonomic or biological variants of Lanulatisphaera laufeldii. The furrows also appear similar to sets of parallel crests and troughs that characterize the ornament of Volleyballia dehlerae n. gen. n. sp. They are distinguished, however, by the fact that V. dehlerae lacks filamentous processes.

Some specimens retain an outer envelope, ~0.1 µm thick, translucent in transmitted light, and covered in 50- to 100-nm-diameter mammillae, regularly spaced and somewhat regularly arranged on the outer surface (Fig. 10.5a, 10.6a). TEM images show that mammillae are continuous with the wall of the envelope; they are not compositionally or structurally distinct from it (Fig. 10.4). In one specimen a partly preserved outer envelope exhibits a ~2-µm-diameter circular opening surrounded by a rim (Fig. 10.3; cf. “circular opening” of Vidal and Ford, Reference Vidal and Ford1985, p. 375). The outer envelope may be irregularly wrinkled or unwrinkled or may be dimpled (Figs. 9.4, 10.6, 11.2, 11.3). We suspect that the dimpling reflects the higher-order structures and, possibly, furrows in the underlying network (discussed previously; Figs. 9.6, 10.6, 10.7).

Possible opercula have been observed in a handful of specimens (Fig. 11.4). They consist of a number of closely packed rounded granulae, similar in size and shape to those found on the opercula of Kaibabia gemmulella. It is not clear whether they are related to the circular openings described in the preceding.

Specimens appear highly variable under transmitted light microscopy. In some, cones are visible (Fig. 12.1). In others, the fibrous network may be visible around the edges of the fossil (Fig 12.3) but otherwise appears as a mottled pattern on the fossil surface. This mottled pattern appears similar to the alveolar structures reported by Vidal and Ford (Reference Vidal and Ford1985) and Vidal (Reference Vidal1976b) in their description of specimens they assigned to Trachysphaeridium laminaritum and which we place in L. laufeldii (see ‘Remarks’). Many specimens appear distinct from both of these, exhibiting, for example, irregularly spotted walls (Fig. 12.5).

Basionym

Trachysphaeridium laufeldi Vidal, Reference Vidal1976b (p. 36–38).

Remarks

Here we assign to a single species specimens that Vidal ascribed to two species, Trachysphaeridium laufeldi and T. laminaritum Timofeev, Reference Timofeev1966 (see Vidal, Reference Vidal1976b; Vidal and Ford, Reference Vidal and Ford1985). Although these specimens appear distinct under light microscopy, we believe they are part of a single species showing continuous variation in form from ‘T. laufeldi’ type (vesicles covered in ~1-µm-long cones) to ‘T. laminaritum’ type (a network of fibers covered by an outer envelope). Definitive confirmation of this is difficult because specimens that under light microscopy have the characteristic ‘alveolar’ appearance of T. laminaritum sensu Vidal (Vidal, Reference Vidal1976b; Vidal and Ford, Reference Vidal and Ford1985) have an intact outer envelope; the filamentous processes that are diagnostic of L. laufeldii are not visible. Nonetheless, several lines of evidence support this assignment. First, a few specimens that do demonstrably have filamentous processes (Fig. 12.3, 12.4) appear similar under transmitted light to specimens of T. laminaritum sensu Vidal—athough their preservation is not good enough to confirm conspecificity. Second, the outer envelopes of those specimens that are confidently interpreted under TLM to be conspecific with T. laminaritum sensu Vidal (Fig. 12.6, 12.7) are similar to the outer envelopes of specimens known to be L. laufeldii (e.g., Fig. 11.2, 11.3) and different from the outer envelopes of other taxa in the assemblage, most notably Culcitulisphaera revelata Riedman and Porter, Reference Riedman and Porter2016, the species most likely to be mistaken for T. laminaritum sensu Vidal (see synonymy and remarks for C. revelata in the preceding). Third, light microscopy observations suggest that T. laminaritum sensu Vidal is among the most common constituents of the Chuar assemblage, whereas SEM observations indicate that L. laufeldii—as represented by the full range of forms from cone-bearing vesicles to those with anastomosing networks—is the most common constituent of Chuar assemblages. If T. laminaritum sensu Vidal is not part of the L. laufeldii species, it’s not clear which of the species observed under SEM it might otherwise be. Finally, in every unit that T. laminaritum sensu Vidal has been reported, T. laufeldii sensu Vidal has also been observed (Vidal, Reference Vidal1976b; Vidal, Reference Vidal1981; Vidal and Ford, Reference Vidal and Ford1985; Riedman and Porter, Reference Riedman and Porter2016; L. Riedman, personal observation), consistent with what would be expected if these two forms are morphological variants of the same species.

The name T. laminaritum has priority over Lanulatisphaera laufeldii—it was erected in 1966 by Timofeev—but it appears to have been erroneously applied to the Chuar specimens. Timofeev’s (Reference Timofeev1966) illustration (hand drawing; pl. 7, fig. 3) shows a specimen that is much larger than the Chuar specimens (vesicles have a diameter of “70 to 250 microns, usually 120–200 microns”; Timofeev, Reference Timofeev1966, p. 36) and is covered by numerous very fine dots (~1 µm scale). (The specimen illustrated by Schopf, Reference Schopf1992, as the holotype of T. laminaritum is apparently in error and is instead a specimen of Culcitulisphaera revelata; see Riedman and Porter, Reference Riedman and Porter2016). The name L. laufeldii is therefore used for this species, with the suffix corrected according to Article 60.12 and 60.C1 of the International Code of Nomenclature for Algae, Fungi, and Plants (Samuelsson, Reference Samuelsson1997).

It is likely that forms described by Vidal and Ford (Reference Vidal and Ford1985) under the designation cf. Cymatiosphaeroides kullingii Knoll, Reference Knoll1984 also belong in L. laufeldii because similar specimens observed under SEM appear to exhibit processes formed via the coalescence of fibers (Fig. 12.8). These are, in any case, distinct from Cymatiosphaeroides Knoll, Reference Knoll1984 emend. Knoll, Swett, and Mark, Reference Knoll, Swett and Mark1991 in that the processes do not connect to an outer wall or thicken at their distal end. In addition, the specimens illustrated here and in Vidal and Ford (Reference Vidal and Ford1985) exhibit only a thin outer envelope, whereas in Cymatiosphaeroides, the outer wall comprises a relatively thick inner layer and as many as six thin outer layers (Knoll, Reference Knoll1984; Knoll et al., Reference Knoll, Swett and Mark1991).

As documented here, L. laufeldii exhibits extensive, continuous variation in morphology (Fig. 25) ranging from specimens with short fibrous processes not yet coalesced (Fig. 9.1) to specimens with fibrous processes coalesced into cones (=T. laufeldi sensu Vidal and Ford, Reference Vidal and Ford1985; Fig. 9.2), specimens with both cones and networks (Fig. 9.3, 9.4,), specimens with extensive networks (Fig. 9.5), and specimens in which the network is organized into a higher-order structure (Fig. 9.6). Similarly wide-ranging variation occurs in other fossil and modern cysts (e.g., Lewis and Hallet, Reference Lewis and Hallett1997; Agić et al., Reference Agić, Moczydłowska and Yin2015) and can reflect either ontogenetic or ecophenotypic variation. For example, in the dinoflagellate Lingulodinium polyedrum (Stein, Reference Stein1883) Dodge, Reference Dodge1989, premature rupture of the outermost membrane surrounding the cyst truncates its morphological development, resulting in cysts with fewer, more irregularly distributed processes and/or processes of very different sizes and shapes (Kokinos and Anderson, Reference Kokinos and Anderson1995). Ecophenotypic variation in cyst morphology has also been documented in dinoflagellates, where differences in the salinity and temperature of seawater in which the cysts formed can influence the length and density of their processes (e.g., Ellegaard, Reference Ellegaard2000; Mertens et al., Reference Mertens2009). Whatever the source of variation in L. laufeldii, this study underscores the importance of examining numerous specimens of varying preservational quality so that a species’ full range of biological and taphonomic variability can be documented (cf. Riedman and Porter, Reference Riedman and Porter2016).

Genus Leiosphaeridia Eisenack, Reference Eisenack1958b

Type species

Leiosphaeridia baltica Eisenack, Reference Eisenack1958b.

Occurrence

Occurs throughout the Chuar Group; widespread in Proterozoic and Phanerozoic assemblages.

Remarks

Leiosphaeridia is a form genus containing smooth-walled spherical to ellipsoidal microfossils. Here we follow Butterfield et al. (Reference Butterfield, Knoll and Swett1994) and divide Leiosphaeridia specimens into one of four species based on to wall thickness (thin walled vs. thicker walled, as determined by degree of opacity) and diameter (<70 µm vs. >70 µm). That this is an artificial classification is evidenced by the difficulty we had in assigning specimens to one of the four species. Wall opacity, which may or may not be an accurate indicator of wall thickness, varies widely and continuously among Chuar specimens. Many specimens exhibit what we considered medium opacity and thus are neither thick walled (L. crassa [Naumova, Reference Naumova1949] and L. jacutica [Timofeev, Reference Timofeev1966]) nor thin walled (L. minutissima [Naumova, Reference Naumova1949] and L. tenuissima [Eisenack, Reference Eisenack1958a]). Similarly, vesicle diameters exhibited unimodal distribution centered at 48 µm; there was no natural break at or around 70 µm (in contrast to that reported by Butterfield et al., Reference Butterfield, Knoll and Swett1994, fig. 4, p. 40). Nonetheless, this classification is broadly useful in that it revealed a possible stratigraphic pattern in the distribution of leiosphaerid sizes: upper Awatubi and Walcott samples showed a preponderance of larger specimens (mostly L. tenuissima) compared to those in the lower Chuar, in which almost all leiosphaerids are small (57% of vesicles are greater than 70 µm in the upper part of the Chuar vs. 12% in the lower part). It is possible that a more biologically realistic taxonomy could be developed for the Chuar leiosphaerids, but that is beyond the scope of this paper.

Leiosphaeridia crassa (Naumova, Reference Naumova1949)

Jankauskas in Jankauskas, Mikhailova, and Hermann, Reference Jankauskas, Mikhailova and Hermann1989

Figure 13.2, 13.6

Figure 13 Leiosphaeridia Eisenack, Reference Eisenack1958b. (1, 5) Leiosphaeridia minutissima (Naumova, Reference Naumova1949) Jankauskas in Jankauskas et al., Reference Jankauskas, Mikhailova and Hermann1989. (1) UCMP 36094a, SP14-63-14; (5) UCMP 36097a, SP14-63-17. (2, 6) Leiosphaeridia crassa (Naumova, Reference Naumova1949) Jankauskas in Jankauskas et al., Reference Jankauskas, Mikhailova and Hermann1989. (2) UCMP 36078, SP14-53-6; (6) UCMP 36094b, SP14-63-14. (3) Leiosphaeridia jacutica (Timofeev, Reference Timofeev1966) Mikhailova and Jankauskas in Jankauskas et al., Reference Jankauskas, Mikhailova and Hermann1989, UCMP 36083e, SP14-63-11. (4) Leiosphaeridia tenuissima Eisenack, Reference Eisenack1958a, note degraded wall, UCMP 36077, SP14-53-20.

1949 Leiotriletes crassus Reference NaumovaNaumova, p. 54, pl. 1, figs. 5, 6, pl. 2, figs. 5, 6.

1989 Leiosphaeridia crassa; Reference Jankauskas, Mikhailova and HermannJankauskas et al., p. 75, pl. 9, figs. 5–10.

Holotype

No holotype was designated by Naumova (Reference Naumova1949). Jankauskas (in Jankauskas et al., Reference Jankauskas, Mikhailova and Hermann1989, p. 75) designated a specimen (plate 1, fig. 3) from Naumova (Reference Naumova1949) as lectotype. However, this specimen was not of a species they synonymized with Leiosphaeridia crassa, but was instead part of Leiotriletes simplicissimus, a species Jankauskas et al., (Reference Jankauskas, Mikhailova and Hermann1989) synonymized with a different species of Leiosphaeridia, L. minutissima.

Description

Solitary, spheroidal, smooth, single-walled vesicles 21 to 70 µm in diameter (mean=44 µm, SD=12 µm, N=28). Wall medium to dark but translucent. Some specimens with medial split.

Holotype

Preparation number 452/1, Biostratigraphy Laboratory, ЛАГЕД AН CCCP Maya River Collection, late Mesoproterozoic/early Neoproterozoic Lakhanda Group, Russia (Timofeev, Reference Timofeev1966: pl. 7, fig. 2).

Description

Solitary, spheroidal, smooth, single-walled vesicles 72 to 102 µm in diameter (mean=92 µm, SD=21 µm, N=6). Vesicle dark but translucent.

Lectotype

No holotype was designated by Naumova (Reference Naumova1949). Jankauskas (in Jankauskas et al., Reference Jankauskas, Mikhailova and Hermann1989, p. 80) designated a specimen of Leiotriletes minutissimus (pl. 1, fig. 1) from Naumova (Reference Naumova1949) as lectotype.

Description

Solitary, spheroidal, smooth, single-walled vesicles 14 to 60 µm in diameter (mean=42 µm, SD=12 µm, N=60). Vesicle medium-thin to very thin walled. Some specimens with medial split (Fig. 13.5, 13.6).

Remarks

The thinnest-walled specimens of L. minutissima (e.g., Fig. 13.1) may be outer envelopes of co-occuring ornamented acritarch species (e.g., Moczydłowska, Reference Moczydłowska2010; see section on ‘Biological affinities of Chuar microfossils’ later in this paper).

Leiosphaeridia tenuissima Eisenack, Reference Eisenack1958a

Figure 13.4

1958a Leiosphaeridia tenuissima Reference EisenackEisenack, p. 391, pl. 1, figs. 2, 3.

1989 Leiosphaeridia tenuissima; Reference Jankauskas, Mikhailova and HermannJankauskas et al., p. 81, pl. 9, figs. 12, 13.

Holotype

Preparation A₃, 3 number 4 from the Dictyonema-shales of the Ordovician Baltic (Eisenack, Reference Eisenack1958a: pl. 1, fig. 2).

Description

Solitary, spheroidal, smooth, single-walled vesicles 72 to 132 µm in diameter (mean=91 µm, SD=16 µm, N=22). Vesicle medium-thin to very thin walled. Some specimens with medial split.

Type species

Microlepidopalla mira n. sp., by monotypy.

Diagnosis

As for type species by monotypy.

Etymology

A combination of the Greek mikros, meaning little, lepidos, meaning scale, and palla, meaning ball, thus ‘little scaly ball,’ in reference to its appearance and similarities to scale-bearing protists.

Remarks

Although the shape and size of Microlepidopalla mira ellipsoids are broadly comparable to those of Eosynechococcus moorei Hofmann, Reference Hofmann1976, their occurrence in tightly formed circular clusters is distinct from the irregularly shaped, loose aggregates of E. moorei. (Other aggregates of cell-like structures, e.g., Sphaerophycus parvum Schopf, Reference Schopf1968 and Gloeotheceopsis aggregata Zhang, Reference Zhang1988, are even less like M. mira, in terms of both the shapes and sizes of their cells and their arrangement in the aggregates.) Furthermore, none of the hundreds of ellipsoids of M. mira that have been observed show any evidence of transverse fission, in constrast to E. moorei (Golubic and Campbell, Reference Golubic and Campbell1979) and other bacterial fossils. Indeed, as will be detailed further in another paper (see Porter et al., Reference Porter, Dehler, Moore, Riedman and Wang2013), these fossils bear strong similarities with scale-bearing protists, including centrohelids, haptophytes, and pompholyxophryids. Given their distinctive appearance, new genus and species names are erected herein for these specimens.

Microlepidopalla mira new species

Figure 14.1–14.7

Figure 14 Microlepidopalla mira n. gen. n. sp. (1) UCMP 36074b, SP12-63-30. (2) UCMP 36091c, SP14-63-14. (3) UCMP 36103, SP14-63-29. (4) UCMP 36074c, SP12-63-30. (5) UCMP 36101, SP14-63-29. (6, 6a) Holotype, UCMP 36104b, SP14-63-29. (7) Transmitted light image of M. mira, UCMP 36094e, SP14-63-14. Same scale bar for (1–6).

?1984 Sphaerophycus aff. parvum; Reference Tynni and UutelaTynni and Uutela, p. 16, figs. 65, 66.

Holotype

UCMP 36104b, sample SP14-63-29, SEM stub 6, Duppa Member, Galeros Formation, Lava Chuar Canyon locality (Fig. 14.6; for location of specimen on stub see Fig. S1).

Diagnosis

Circular clusters, ~10 to 30 µm in diameter, composed of numerous overlapping organic-walled ellipsoidal structures, 2 to 8 µm in length and 1 to 4 µm in width.

Occurrence

Tanner, Jupiter, Carbon Canyon, Duppa, and Awatubi members, Chuar Group; late Tonian Moosehorn Lake Formation, Uinta Mountain Group, Utah (SMP personal observation). Possible occurrences in the poorly constrained ?Mesoproterozoic Muhos Formation, western Finland (Tynni and Uutela, Reference Tynni and Uutela1984).

Description

Circular or subcircular clusters of flattened ellipsoids; ellipsoids 2.2 to 7.4 µm in length (mean=4.0 µm, SD=1.0 µm, N=164), 1.3 to 3.3 µm in width (mean=2.1 µm, SD=0.4 µm, N=156), and with aspect ratios 1.1 to 3.4 (mean=1.9, SD=0.4, N=153). Circular clusters 9 to 31 µm in diameter (mean=19 µm, SD=8 µm, N=19). Ellipsoids may also occur singly, sometimes lying atop other microfossils. Within a cluster, ellipsoids may overlap but are not imbricated; some lie fully on top of others such that their entire outline is visible.

Etymology

From the Latin mira, meaning strange and wonderful, with reference to the fossil’s aesthetic beauty and to the wonder one feels discovering beautiful fossils in rocks so old.

Remarks

The wide variation in cluster diameter (cf. Fig. 14.4, 14.5 vs. Fig. 14.6) may point to the presence of more than one species in the Chuar assemblage, but we were unable to reject the null hypothesis that the distribution of cluster diameters is unimodal, and therefore place these specimens in a single species.

Genus Navifusa Combaz, Lange, and Pansart, Reference Combaz, Lange and Pansart1967 ex Eisenack, Reference Eisenack1976

Type species

Navifusa navis (Eisenack, Reference Eisenack1938) Eisenack, Reference Eisenack1976

Navifusa majensis Pyatiletov, Reference Pyatiletov1980

Figure 23.1

1980 Navifusa majensis Reference PyatiletovPyatiletov, p. 144, fig. 1.

1994 Navifusa majensis; Reference Hofmann and JacksonHofmann and Jackson, p. 20, fig. 15.1–15.4.

Holotype

ИГиГ СО АН СССР Preparation number 685 from Khabarovsk Krai, left bank of Maya River, late Mesoproterozoic–early Neoproterozoic Lakhanda Group, third subsuite, Russia (Pyatiletov, Reference Pyatiletov1980, fig. 1a).

Type species

Palaeastrum dyptocranum Butterfield in Butterfield et al., Reference Butterfield, Knoll and Swett1994, by monotypy.

Diagnosis

As for type species (emended from Butterfield et al., Reference Butterfield, Knoll and Swett1994).

Remarks

Butterfield et al. (Reference Butterfield, Knoll and Swett1994) provided a separate diagnosis for the genus Palaeastrum and for its single species, P. dyptocranum, differentiating the latter from the former by stating that the latter is “[a] species of Palaeastrum with cells 10–25 µm in diameter” (p. 20). However, given that there are no other species within the genus with which to compare P. dyptocranum, it is not possible to know the range of cell diameters that delimit this species. Indeed, a specimen in the collection described here falls slightly outside these boundaries, and rather than emend the range of cell diameters listed in the species diagnosis so as to include this specimen (and leave open the necessity for future taxonomists to emend it again if specimens with slightly smaller or larger cell sizes are discovered), we have removed reference to cell diameters altogether and have produced a single diagnosis for both the species and the genus. This diagnosis is similar to the original diagnosis provided for the genus but is modified to include the characteristic of an enclosed three-dimensional (spheroidal or ellipsoidal) colony.

Palaeastrum dyptocranum Butterfield in Butterfield, Knoll, and Swett, Reference Butterfield, Knoll and Swett1994

Figure 15.1–15.3

Figure 15 Palaeastrum dyptocranum Butterfield in Butterfield et al., Reference Butterfield, Knoll and Swett1994. (1, 2) Nearly complete colonies showing ellipsoidal shape. (1, 1a) UCMP 36096g, SP14-63-17. Black arrows indicate several of the attachment discs; others are also visible in the image. (2) SP14-63-11. (3) Constituent cells are partly degraded and difficult to see; the dark circular and elliptical structures, most easily seen in the center of the image, are attachment discs, UCMP 36096f, SP14-63-17.

1994 Palaeastrum dyptocranum Butterfield, in Reference Butterfield, Knoll and SwettButterfield et al., p. 18, fig. 5A–C.

2009 Palaeastrum; Reference ButterfieldButterfield, fig. 1E–G.

2015 Palaeastrum dyptocranum; Reference Vorob’eva, Sergeev and PetrovVorob’eva et al., p. 217, fig. 8.1, 8.3, 8.4.

Holotype

HUPC 62708, slide 86-G-62-46, England Finder coordinates M-48-1, late Tonian Algal Dolomite Member, Svanbergfjellet Formation, Geerabukta, Svalbard (Butterfield et al., Reference Butterfield, Knoll and Swett1994, fig. 5A, p. 18).

Diagnosis

Colonial, spheroidal to ellipsoidal cells with prominent intercellular attachment discs; discs circular with a reinforced rim. Colonies monostromatic, forming enclosed spheroidal or ellipsoidal structures hundreds of micrometers in diameter (emended from Butterfield et al., Reference Butterfield, Knoll and Swett1994).

Occurrence

Tanner Member, Chuar Group; Neoproterozoic Svanbergfjellet Formation, Akademikerbreen Group, Svalbard (Butterfield et al., Reference Butterfield, Knoll and Swett1994; Butterfield, Reference Butterfield2009); and Mesoproterozoic Kotuikan Formation, northern Siberia (Vorob’eva et al., Reference Vorob’eva, Sergeev and Petrov2015).

Description

Ellipsoidal to spheroidal colonies, 210 to 360 µm in width (mean=270 µm; N=5) and 360 to 580 µm in length (mean=360 µm, N=5), consisting of a single layer of ellipsoidal to spheroidal cells 9 to 17 µm in diameter (mean=14µm, N=25) attached to each other via thickened discs 3 to 5 µm in diameter (mean=4 µm; N=27). In some specimens the cell walls are degraded and only the attachment discs are clearly visible, suggesting that the latter have greater preservation potential (Fig. 15.2, 15.3; cf. Butterfield et al., Reference Butterfield, Knoll and Swett1994). Typically four attachment discs per cell; hundreds of cells per colony.

Remarks

Butterfield et al. (Reference Butterfield, Knoll and Swett1994) placed Palaeastrum in the Order Chlorococcales, Division Chlorophyta, noting that the extant chlorococcalean algae Pediastrum and Coelastrum also form multicellular coenobia in which the cells are attached to each other via differentiated ‘plaques’ (e.g., Marchant, Reference Marchant1977). Because of the subsequent discovery of complete specimens illustrating that Palaeastrum coenobia formed hollow ellipsoids similar to those formed in the extant alga Hydrodictyon, Butterfield (Reference Butterfield2009, p. 204) stated that Palaeastrum could be “reliably assigned to the Hydrodictyaceae (Sphaeropleales, Chlorophyceae, Chlorophyta).” (Note that many members of the Chlorococcales including Pediastrum and Coelastrum are now considered part of the order Sphaeropleales; Deason et al., Reference Deason, Silva, Watanabe and Floyd1991; Lewis and McCourt, Reference Lewis and McCourt2004.)

Unfortunately, data on the phylogenetic distribution of Palaeastrum’s diagnostic characters among extant taxa are either not known or not easily accessible. The data that are available suggest that these characters are not restricted to the Hydrodictyaceae; Coelastrum (Scenedesmidaceae; Tippery et al., Reference Tippery, Fučiková, Lewis and Lewis2012), for example, also possesses attachment plaques and three-dimensional coenobia (Marchant, Reference Marchant1977). Furthermore, molecular phylogenetic analyses indicate that three-dimensional coenobia evolved at least twice within the Hydrodictyaceae (Buchheim et al., Reference Buchheim, Buchheim, Carlson, Braband, Hepperle, Krienitz, Wolf and Hegewald2005), raising the possibility that similarities with Palaeastrum reflect convergent evolution. More generally, there is accumulating evidence that within the green algae, morphology can be phylogenetically misleading (Lewis and McCourt, Reference Lewis and McCourt2004; McManus and Lewis, Reference McManus and Lewis2011). Therefore, while it is reasonable to suggest that Palaeastrum may be part of the Sphaeropleales, a monophyletic group that includes taxa that do have a good fossil record (Colbath and Grenfell, Reference Colbath and Grenfell1995), we are not at all confident in that assignment, nor are we strongly confident in the assignment to the Chloroplastida (=Viridiplantae).

Genus Rugosoopsis Timofeev and Hermann, Reference Timofeev and Hermann1979

Type species

Rugosoopsis tenuis Timofeev and Hermann, Reference Timofeev and Hermann1979.

Rugosoopsis tenuis Timofeev and Hermann, Reference Timofeev and Hermann1979

Figure 16.1

Figure 16 (1) Rugosoopsis tenuis Timofeev and Hermann, Reference Timofeev and Hermann1979, UCMP 36094c SP14-63-14. (2) Siphonophycus septatum (Schopf, Reference Schopf1968) Knoll, Swett, and Mark, Reference Knoll, Swett and Mark1991, note longitudinal splits in some (e.g., black arrows), UCMP 36083g, SP14-63-11. (3) Siphonophycus typicum (Hermann, Reference Hermann1974) Buttterfield in Butterfield et al., Reference Butterfield, Knoll and Swett1994, note longitudinal split, UCMP 36083h, SP14-63-11. (4) Siphonophycus robustum (Schopf, Reference Schopf1968) Knoll, Swett, and Mark, Reference Knoll, Swett and Mark1991, UCMP 36100, SP14-63-24.

1979 Rugosoopsis tenuis Reference Timofeev and HermannTimofeev and Hermann, p. 139, pl. 29, figs. 5, 7.

1994 Rugosoopsis tenuis; Reference Butterfield, Knoll and SwettButterfield et al., p. 62, figs. 25A-D, 27B.

Holotype

Preparation number 1-22/1-77/1, late Mesoproterozoic–early Neoproterozoic Lakhanda Group, Maya River, Khabarovsk Krai, Siberia (Timofeev and Hermann, Reference Timofeev and Hermann1979, pl. 29, fig. 7).

Occurrence

Tanner Member, Chuar Group; the Neoproterozoic Svanbergfjellet Formation, Svalbard (Butterfield et al., Reference Butterfield, Knoll and Swett1994), Lone Land Formation, Franklin Mountains, Canada (Samuelsson and Butterfield, Reference Samuelsson and Butterfield2001), Alinya Formation, Officer Basin (Riedman and Porter, Reference Riedman and Porter2016), and the late Mesoproterozoic–early Neoproterozoic Lakhanda Group, Siberia (Timofeev and Hermann, Reference Timofeev and Hermann1979).

Description

Rugose filaments 32 to 41 µm in width (N=3); wrinkles are ~1 to 3 µm in width and are roughly perpendicular to filament axis. All three specimens are broken and reach only 65 to 88 µm in length. One specimen exhibits an unwrinkled portion at one end.

Type species

Siphonophycus kestron Schopf, Reference Schopf1968.

Occurrence

Occurs throughout the Chuar Group; widespread in Proterozoic and Phanerozoic assemblages.

Remarks

Siphonophycus is a form genus that encompasses smooth-walled, nonbranching, nonseptate tubular filaments with open or closed hemispherical terminations (Knoll et al., Reference Knoll, Swett and Mark1991). Species are distinguished on the basis of filament width.

Siphonophycus robustum (Schopf, Reference Schopf1968) Knoll, Swett, and Mark, Reference Knoll, Swett and Mark1991

Figure 16.4

1968 Eomycetopsis robusta Reference SchopfSchopf, p. 685, pl. 82, figs. 2, 3 and pl. 83, figs. 1–4.

1991 Siphonophycus robustum; Reference Knoll, Swett and MarkKnoll et al., p. 565, fig. 10.3, 10.5.

1994 Siphonophycus robustum; Reference Butterfield, Knoll and SwettButterfield et al., p. 64, fig. 26A, G.

Holotype

Thin section Bit. Spr. 10-1, Paleobotanical collections, Harvard University number 58491 from Neoproterozoic Bitter Springs Formation, Amadeus Basin, Australia (Schopf, Reference Schopf1968, pl. 83, fig. 1).

Description

Filaments 2 to 4 µm in diameter (N=7). May occur singly or as aggregates.

Holotype

Thin section Bit/Spr 6–3, Paleobotanical collections, Harvard University, number 58527 from the Neoproterozoic Bitter Springs Formation, Amadeus Basin, Australia (Schopf, Reference Schopf1968, pl. 86, fig. 11).

Description

Filaments 1 to 2 µm in diameter (N=8). Several specimens exhibit longitudinal splits (Fig. 16.2). May occur singly or as aggregates.

Holotype

Preparation number 49/2T, Neoproterozoic Miroyedikha Formation, Krasnoyarsk Krai in Turukhansk region, near Maya River, Siberia (Hermann, Reference Hermann1974, p. 7, pl. 6, figs. 1, 2).

Description

Filaments 4 to 8 µm in diameter (N=10). One specimen exhibits a longitudinal split (Fig. 16.3).

Type species

Squamosphaera colonialica (Jankauskas, Reference Jankauskas1979b) Tang et al., Reference Tang, Pang, Yuan, Wan and Xiao2015, by monotypy.

Diagnosis

As for type species by monotypy (emended from Tang et al., Reference Tang, Pang, Yuan, Wan and Xiao2015).

Remarks

Vidal and Ford (Reference Vidal and Ford1985) described specimens of Squamosphaera colonialica from the Chuar Group under the name Satka colonialica Jankauskas, Reference Jankauskas1979b. The type species of Satka, S. favosa Jankauskas, Reference Jankauskas1979a, is characterized by a wall composed of numerous polygonal plates; studies of other populations attributed to S. favosa show that these plates are sutured together and can break apart along these sutures (Hofmann and Jackson, Reference Hofmann and Jackson1994, fig. 18.26; Javaux et al., Reference Javaux, Knoll and Walter2004, fig. 3a–f). By contrast, the holotype of Squamosphaera colonialica—as well as better-known collections from the Chuar and elsewhere—consists of a single continuous wall with numerous rounded bulges, not the plates diagnostic of Satka. The similarities between Satka favosa and Squamosphaera colonialica therefore appear to be superficial. Recognizing these differences, Tang et al. (Reference Tang, Pang, Yuan, Wan and Xiao2015) removed S. colonialica from the genus Satka and placed it in a new genus, Squamosphaera. We follow that here, although we emend the diagnosis of this monotypic genus so that it is the same as that for the species and modify the species diagnosis to accommodate the Chuar material (see the following).

Squamosphaera colonialica (Jankauskas, Reference Jankauskas1979b) Tang, Pang, Yuan, Wan, and Xiao, Reference Tang, Pang, Yuan, Wan and Xiao2015

Figure 17.1–17.7

Figure 17 Squamosphaera colonialica (Jankauskas, Reference Jankauskas1979b) Tang et al., Reference Tang, Pang, Yuan, Wan and Xiao2015. (1, 1a) Toroidal specimen, UCMP 36096c, SP14-63-17. (2, 2a) Specimen with subcircular outline, UCMP 36096d, SP14-63-17. (3) Irregularly shaped specimen, UCMP 36096b, SP14-63-17. (4) UCMP 36084c, SP14-63-11. (5) UCMP 36097b, sample SP14-63-17. (6) UCMP 36075a, SP12-63-30. (7, 7a, 7b) UCMP 36096e, SP14-63-17. (7b) Note pocked texture of wall, reflecting taphonomic degradation.

?1966 Gloeocapsomorpha hebeica Reference TimofeevTimofeev, p. 43, pl. 4, fig. 1.

?1976 “Sphaeromorphs in the process of division”; Reference Timofeev, Hermann and MikhailovaTimofeev et al., pl. 8, figs. 6, 8, 9.

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

?1980 Synsphaeridium sp.; Reference Tynni and DonnerTynni and Donner, pl. I.7.

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

1985 Satka colonialica; Reference Vidal and FordVidal and Ford, p. 369, fig. 6.

1989 Satka colonialica; Reference Jankauskas, Mikhailova and HermannJankauskas et al., p. 51, pl. 4, figs. 4, 7.

1992 Satka colonialica; Reference SchopfSchopf, pl. 42B.

non 1992a Satka compacta; Reference Zang and WalterZang and Walter, p. 93 fig. 69F, H.

?1994 Satka colonialica; Reference Yin and SunYin and Sun, p. 107, fig. 5G.

non 1994 Satka colonialica; Reference Yin and SunYin and Sun, p. 107, fig. 7K, L.

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

1999 Satka colonialica; Reference CotterCotter, p. 77, fig. 7C.

1999 Satka colonialica; Reference Samuelsson, Dawes and VidalSamuelsson et al., fig. 4G.

non 1999 Satka colonialica; Reference Yin and GuanYin and Guan, p. 134, fig. 7.1, 7.3, 7.8, 7,9.

2009 Satka colonialica; Reference Nagy, Porter, Dehler and ShenNagy et al., fig. 1L.

non 2011 Satka sp. cf. S. colonialica; Reference Couëffé and VecoliCouëffé and Vecoli, fig. 7.2.

2015 Squamosphaera colonialica; Reference Tang, Pang, Yuan, Wan and XiaoTang et al., p. 312, figs. 12, 13.

Holotype

ЛитНИГРИ, number 16-62-4762/22, slide 1. Well Kabakovo-62, 4762–4765 m. Neoproterozoic Zigazino-Komarovo Formation, Ufa, Bashkirian Urals (Jankauskas, Reference Jankauskas1979b, fig. 4).

Diagnosis

Single-walled, spheroidal, tomaculate, toroidal, or irregularly shaped vesicles with an irregular outline characterized by numerous broadly domical bulges. Vesicles typically 80–500 µm in maximum dimension; bulges typically 5–30 µm in basal width (emended from Jankauskas, Reference Jankauskas1979b; Tang et al., Reference Tang, Pang, Yuan, Wan and Xiao2015).

Occurrence

Tanner, Jupiter, Carbon Canyon, and Duppa members, Chuar Group; depths of 4,762–4,765 m in Kobakovo 62 drill hole, Ufa, Bashkirian Urals (Jankauskas, Reference Jankauskas1979b); Glasgowbreen and Oxfordbreen formations, Veteranen Group, Svalbard (Knoll and Swett, Reference Knoll and Swett1985); Iernovskaya, Chernorechenskaya, Poropelonskaya, and Karuyarvinskaya formations, Kildinskaya Group, Kola Peninsula, Russia (Samuelsson, Reference Samuelsson1997); Steptoe Formation, Kanpa 1A drill core, and Kanpa and Hussar formations, Hussar 1 drill core, Officer Basin, Australia (Cotter, Reference Cotter1999); Imilik Formation, Narssârssuk Group; Steensby Land and Kap Powell formations, Dundas Group, and Qaanaaq and Robertson Fjord formations, Baffin Bay Group, Thule Supergroup, northwest Greenland (Samuelsson et al., Reference Samuelsson, Dawes and Vidal1999); Gouhou Formation, Huaibei region, North China (Tang et al., Reference Tang, Pang, Yuan, Wan and Xiao2015). Squamosphaera colonialica has also been noted (as Satka colonialica) but not described or illustrated from the lower part of the upper Visingsö Group (Vidal and Ford, Reference Vidal and Ford1985) and the Red Pine Shale, Uinta Mountain Group, Utah (Nagy and Porter, Reference Nagy and Porter2005; Dehler et al., Reference Dehler, Porter, de Grey, Sprinkel and Brehm2007). Late Mesoproterozoic to Tonian in age.

Description

Spherical (Fig. 17.2), tomaculate (Fig. 17.4, 17.5, 17.7), toroidal (Fig. 17.1), or irregularly shaped (Fig. 17.3) vesicles ~100 to 410 µm in maximum dimension (mean=160 µm, SD =74 µm, N=22), bearing numerous rounded bulges. Bulges may be clearly distinct, occurring as hemispherical outpocketings (e.g., Fig. 17.4–17.7), or they may be most clearly visible as a slight scalloped pattern along the periphery of the vesicle (Fig. 17.1–17.3). The vesicles are empty, but folding and compaction can make it appear as though internal bodies are present (e.g., Fig. 17.6, 17.7).

The size of the bulges ranges from 10 to 35 µm (mean=17 µm, SD=5 µm, N=84; size of bulges measured at widest span). Within a single vesicle, the range of sizes is much narrower, with diameters of individual bulges typically within 4 µm of each other (e.g., 16 to 20 µm diameter). There is little correlation (r=−0.09, N=22) between the diameter of the bulges and the maximum dimension of the vesicle. In some specimens viewed under TLM, the wall appears to have a subtle texture, but evidence from specimens observed using SEM suggests that the wall is in fact smooth and that the subtle texture likely arises from the impressions of minerals that grew into the wall after deposition (Fig. 17.7b).

Remarks

In the Chuar assemblage, the size and shape of the vesicles and the number, size, and expression of the bulges is highly variable. It is possible this reflects lumping of several distinct species, but we were unable to identify convincing gaps in the variation that would indicate this is the case. Instead we interpret this to represent intraspecific—possibly ecophenotypic—variation, and group all of the Chuar specimens into a single highly variable species.

Vidal and Ford (Reference Vidal and Ford1985) suggested that the undulating outline of the vesicle (=‘envelope’ of Vidal and Ford, Reference Vidal and Ford1985) reflects compression around colonial clusters of spherical cells, a view that was followed by Knoll and Swett (Reference Knoll and Swett1985). They illustrate one specimen (Vidal and Ford, Reference Vidal and Ford1985, fig. 6D–F) that appears to retain one of these cells. However, the cell appears to be outside the vesicle, and although it is similar in size to the bulges on the vesicle, it is possible that it is a small leiosphaerid, unrelated to the vesicle, that became fortuitously attached after death. While there are fossils in the Chuar Group that consist of numerous tightly packed spherical bodies (e.g., Fig. 18.3), these are distinct from S. colonialica in that they are not surrounded by an outer envelope. (These have been placed in open nomenclature in the form genus Synsphaeridium.) Many of the S. colonialica specimens in the Chuar Group—as well as the holotype specimen from the Urals and specimens from elsewhere (e.g., Tang et al., Reference Tang, Pang, Yuan, Wan and Xiao2015)—show no evidence of rupture, indicating that the absence of internal bodies does not simply reflect their departure from the vesicle.

Figure 18 Synsphaeridium Eisenack, Reference Eisenack1965. (1) UCMP 36084a, SP14-63-11. (2) Note dark circular bodies on some cells, UCMP 36084b, SP14-63-11. (3) Specimen with rounded margins suggesting preservation of the original outline of the colony, UCMP 36083f, SP14-63-11.

Noting the lack of evidence for internal bodies, Tang et al. (Reference Tang, Pang, Yuan, Wan and Xiao2015) described the bulges on the vesicle wall as “domical processes” that “freely communicate with the vesicle cavity” rather than as “circular impressions on the wall” (p. 310). However, the absence of preserved internal bodies does not imply that they were not once there; taphonomic studies of modern filamentous cyanobacteria, for example, show that extracellular sheaths are more likely to be preserved than trichomes (Bartley, Reference Bartley1996). Given the uncertainty in the interpretation of these features, we have emended the diagnosis of Tang et al. (Reference Tang, Pang, Yuan, Wan and Xiao2015) so that it refers to bulges rather than processes. We believe that this change leaves open the question of how they arose—either as processes ornamenting a vesicle wall (cf. Tang et al., Reference Tang, Pang, Yuan, Wan and Xiao2015) or, as favored here, impressions of internal cells no longer preserved (cf. Knoll and Swett, Reference Knoll and Swett1985; Vidal and Ford, Reference Vidal and Ford1985). We have also emended the diagnosis to accommodate the range of vesicle shapes exhibited by the Chuar material (including toroidal and irregular).

Possible occurrences of Squamosphaera colonialica include a single specimen (and the presumed holotype) of Gloeocapsomorpha hebeica Timofeev, Reference Timofeev1966. Although the hand-drawn sketch suggests a single vesicle with multiple bulges, the accompanying text describes the species as “[a]n accumulation of large, thin, smooth subspherical coalesced vesicles,” i.e., an aggregate of leiosphaerids similar to Synsphaeridium sp. (Timofeev, Reference Timofeev1966, p. 43). The Chuar specimens are therefore not assigned to G. hebeica, which otherwise would have priority.

Other possible occurrences of S. colonialica are three of nine specimens illustrated by Timofeev et al. (Reference Timofeev, Hermann and Mikhailova1976) as “[s]phaeromorphs in the process of division” (pl. 8, figs. 6, 8, 9). Although they appear similar to smaller specimens of S. colonialica described here, their more pronounced bulges and co-occurrence with two- and three-celled dividing sphaeromorphs suggest they may indeed be dividing sphaeromorphs as well. Definite occurrences of S. colonicalica include those reported by Knoll and Swett (Reference Knoll and Swett1985), Samuelsson (Reference Samuelsson1997), Cotter (Reference Cotter1999), and Samuelsson et al. (Reference Samuelsson, Dawes and Vidal1999).

The organic-walled vesicles of Timanisphaera apophysa Vorob’eva, Sergeev, and Knoll, Reference Vorob’eva, Sergeev and Knoll2009 bear numerous hemispherical processes similar to the bulges of S. colonialica. However, the processes are much greater in size (50 to 90 µm wide vs. 10 to 35 µm), and the vesicles of T. apophysa (N=18) do not show the range of unusual shapes observed in the S. colonialica specimens studied here (N=30).

Several specimens of aggregated cells assigned in the literature to Satka colonialica or Satka cf. Satka colonialica are here excluded from Squamosphaera colonialica because they do not show evidence of an outer envelope (cf. Fig. 18.3): specimens described as Satka compacta Zang and Walter, Reference Zang and Walter1992a, ascribed to Satka colonialica by Samuelsson (Reference Samuelsson1997); specimens described as Satka colonialica by Yin and Sun (Reference Yin and Sun1994) and Yin and Guan (Reference Yin and Guan1999); and specimens described as Satka cf. Satka colonialica by Couëffé and Vecoli (Reference Couëffé and Vecoli2011).

Genus Synsphaeridium Eisenack, Reference Eisenack1965

Type species

Synsphaeridium gotlandicum Eisenack, Reference Eisenack1965.

Synsphaeridium spp.

Figure 18.1–18.3

Occurrence

Tanner, Jupiter, and Awatubi members, Chuar Group. Widespread in Proterozoic and Phanerozoic rocks.

Description

Aggregates of organic-walled spheroidal vesicles 8 to 29 µm in diameter (mean=16 µm, SD=5 µm, N=64 vesicles in 16 colonies). Tight packing of vesicles may result in a polygonal outline of each vesicle. Areas of vesicle contact are typically more resistant to degradation (e.g., Fig. 18.1). Aggregates vary with respect to the tightness of vesicle packing and the arrangement of vesicles (from monostromatic to three-dimensional, ellipsoidal colonies). Within four of the aggregates, vesicles exhibit dark circular spots (Fig. 18.2). These appear to be part of or fused to the vesicle wall (cf. Pang et al., Reference Pang, Tang, Schiffbauer, Yao, Yuan, Wan, Chen, Ou and Xiao2013) because they are in the same focal plane. The spots range from 2.4 to 3.7 µm in diameter (mean=2.9 µm, SD=0.4 µm, N=13 spots in 4 colonies) and occur in vesicles 8 to 13 µm in diameter. Spots are not uniformly present throughout an aggregate; a vesicle without a spot may lie adjacent to a vesicle with one.

Remarks

Simple characters unite this group, which is almost certainly polyphyletic. A number of generic names have been applied to aggregates of smooth-walled vesicles, but these overlap to varying degrees in their diagnoses (see Riedman and Porter, Reference Riedman and Porter2016), and it is not clear that parsing out the Chuar specimens into different taxa would be either meaningful or possible. We therefore follow Riedman and Porter (Reference Riedman and Porter2016) and place these specimens in open nomenclature in the earliest erected genus of smooth-walled aggregates, Synsphaeridium Eisenack (Reference Eisenack1965).

Genus Valeria Jankauskas, Reference Jankauskas1982

Type Species

Valeria lophostriata (Jankauskas, Reference Jankauskas1979b) Jankauskas, Reference Jankauskas1982.

Valeria lophostriata (Jankauskas, Reference Jankauskas1979b) Jankauskas, Reference Jankauskas1982

Figure 19.1–19.3

Figure 19 Valeria lophostriata (Jankauskas, Reference Jankauskas1979b) Jankauskas, Reference Jankauskas1982. (1) SP14-63-11. (2, 2a) Specimen with striae visible on outer surface, UCMP 36095, SP14-63-17. (3, 3a) Specimen partly split with the two halves enrolled to form a fusiform shape. (3a) Closeup of specimen showing the striations characteristic of this species, UCMP 36075b, SP12-63-30.

1979b Kildinella lophostriata Reference JankauskasJankauskas, p. 53, fig. 1.13–1.15.

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

1989 Valeria lophostriata; Reference Jankauskas, Mikhailova and HermannJankauskas et al., p. 86, pl. 16, figs. 1–5.

1995 Valeria lophostriata; Reference ZangZang, p. 170, fig. 28I.

1999 Valeria lophostriata; Reference Samuelsson, Dawes and VidalSamuelsson et al., fig. 8E.

2001 Valeria lophostriata; Reference Javaux, Knoll and WalterJavaux et al., fig. 1D.

2004 Valeria lophostriata; Reference Javaux, Knoll and WalterJavaux et al., fig. 2F–I.

2009 Valeria lophostriata; Reference Nagy, Porter, Dehler and ShenNagy et al., fig. 1A, B

2009 Valeria lophostriata; Reference NagovitsinNagovitsin, p. 144, fig. 4E.

?2011 Valeria lophostriata; Reference Couëffé and VecoliCouëffé and Vecoli, fig. 6.4.

?2012 dark-walled megasphaeric coccoid; Reference Battison and BrasierBattison and Brasier, fig. 8B.

2015 Valeria lophostriata; Reference Tang, Pang, Yuan, Wan and XiaoTang et al., p. 315, fig. 11.

2016 Valeria lophostriata; Reference Riedman and PorterRiedman and Porter, p. 862, fig. 4.1.

(For additional synonymy, see Jankauskas et al., Reference Jankauskas, Mikhailova and Hermann1989; Hofmann, Reference Hofmann1999, table 1)

Holotype

ЛитНИГРИ, number 16-62-4762/16, sp. 1, DH Kabakovo 62 drill core, depth 4,762 to 4,765 meters, Neoproterozoic Zigazino-Komarovo Formation, southern Urals (Jankauskas, Reference Jankauskas1979b, fig. 1.14).

Occurrence

Tanner and Jupiter members, Chuar Group; widely distributed in late Paleoproterozoic through Tonian rocks.

Description

Spherical vesicles 55 to 180 µm in diameter (mean=85 µm, SD=46 µm, N=6) with concentric ridges spaced 0.5 to 1.0 µm apart; circular structures ~3 µm in diameter are located at each pole (Fig. 19.1). Javaux et al. (Reference Javaux, Knoll and Walter2004) showed that these ridges are on the inner surface of the vesicle; their presence is also visible under SEM on the outer surface of the wall (Fig. 19.2), although this may reflect penetration of the wall by the electron beam, compression of the vesicle, or thinning of the outer wall associated with degradation, rather than biological form. Some specimens split along striae; one specimen partly split with the two halves enrolled to form a fusiform shape (Fig. 19.3; cf. Javaux et al., Reference Javaux, Knoll and Walter2004; Peng et al., Reference Peng, Bao and Yuan2009).

Type species

Vidalopalla verrucata (Vidal in Vidal and Siedlecka, Reference Vidal and Siedlecka1983) Riedman and Porter, Reference Riedman and Porter2016, by monotypy.

Remarks

The Chuar specimen differs sufficiently from the type material that placement in the type and only species of Vidalopalla, V. verrucata, is in question. Nonetheless, those differences are of a quantitative rather than qualitative nature (size and spacing of verrucae; size of vesicles), justifying their placement in the genus Vidalopalla Riedman and Porter, Reference Riedman and Porter2016.

Vidalopalla cf. verrucata (Vidal in Vidal and Siedlecka, Reference Vidal and Siedlecka1983)

Riedman and Porter, Reference Riedman and Porter2016

Figure 20.1

Figure 20 Vidalopalla cf. verrucata (Vidal in Vidal and Siedlecka, Reference Vidal and Siedlecka1983) Riedman and Porter, 2016. (1, 1a) UCMP 36085b, SP14-63-12.

cf. 1981 Kildinella sp. B; Reference VidalVidal p. 26, fig. 13A–D.

cf. 1983 Kildinosphaera verrucata Vidal; Vidal and Siedlecka, Reference Vidal and Siedlecka1983, p. 62, fig. 5C.

cf. 1985 Kildinosphaera verrucata; Reference Vidal and FordVidal and Ford, p. 363, fig. 4A.

cf. 2016 Vidalopalla verrucata; Reference Riedman and PorterRiedman and Porter, p. 870, fig. 11.3, 11.4, 11.8.

Holotype

Specimen E74–02: V/47 from the Neoproterozoic Ekkerøy Formation, Store Ekkerøy (locality 14), Varanger Peninsula, East Finnmark, Norway (Vidal, Reference Vidal1981, fig. 13A–D); in keeping with the original designation by Vidal and Siedlecka (Reference Vidal and Siedlecka1983).

Description

Organic-walled spheroidal vesicle 32 µm in diameter covered in rounded verrucae 0.2 to 0.4 µm in diameter. Verrucae are closely spaced, nearly touching.

Remarks

The Chuar specimen differs from the type material of V. verrucata in several ways, most notably the spacing of the verrucae (>1 µm apart in the type material vs. 0.1 µm in the Chuar specimens). The verrucae are also smaller in the Chuar material (0.2–0.4 µm in diameter vs. 1–1.5 µm in the type material; Vidal, Reference Vidal1981), as is the vesicle (32 µm in diameter vs. 40 to 135 µm; Vidal, Reference Vidal1981; Vidal and Siedlecka, Reference Vidal and Siedlecka1983). Nonetheless, there are enough similarities between the specimen described here and other collections of V. verrucata (e.g., Riedman and Porter, Reference Riedman and Porter2016) that we cannot rule out the possibility that additional material will support inclusion of this specimen in V. verrucata. Vidal and Ford (Reference Vidal and Ford1985) reported V. verrucata from the Chuar Group, and both their description and accompanying image (fig. 4A) are consistent with that taxonomic assignment. Thus, V. verrucata does occur in the Chuar Group—in the Awatubi Member, at least (Vidal and Ford, Reference Vidal and Ford1985)—and it is possible the specimen described here represents an end member of a species that varied widely in both vesicle size and verrucae size and spacing.

Genus Volleyballia new genus

Type species

Volleyballia dehlerae n. sp., by monotypy.

Diagnosis

As for type species.

Etymology

Named for pattern of the vesicle wall, which is similar in appearance to that of a volleyball.

Remarks

Although other acritarch species exhibit striations (see ‘Remarks’ in the following), none are sufficiently similar to suggest a close relationship with V. dehlerae. Thus we have chosen to erect a new genus for this species.

Volleyballia dehlerae new species

Figure 21.1–21.7

Figure 21 Volleyballia dehlerae n. gen. n. sp. (1, 1a, 1b) Holotype; UCMP 36080d, SP14-63-11, England Finder coordinate Q49. (2, 2a) UCMP 36086c, SP14-63-12. (3) UCMP 36081a, SP14-63-11. (4, 4a) UCMP 36079b, SP14-63-11. (5) UCMP 36089a, SP14-63-14. (6) UCMP 36083i, SP14-63-11. (7, 7a) 36081b, SP14-63-11. (7a) View of tilted (52°) specimen that has been cut using a focused ion beam. Specimen is partially coated with platinum (Pt); black arrows point to ridges on upper surface of vesicle wall.

?1995 Striasphaera radiata Liu in Gao, Xing, and Liu, pp. 14, 20, pl. 2, figs. 10, 11.

?1995 Striasphaera irregularia Liu in Gao, Xing, and Liu, pp. 14, 20, pl. 2, fig. 12.

?1996 Unnamed form; Reference KnollKnoll, pl. 5, fig. 11.

1999 ?Leiosphaeridia sp.; Reference CotterCotter, fig. 8H.

2000 Form 1; Reference Simonetti and FairchildSimonetti and Fairchild, p. 25, fig. 8S.

2009 Unnamed form A; Reference Nagy, Porter, Dehler and ShenNagy et al., fig. 1D.

2016 Volleyballia dehlerae; Reference Riedman and PorterRiedman and Porter, p. 876, fig. 3.9–3.14.

Holotype

UCMP 36080d, sample SP14-63-11, SEM slide=ker-2, EF=Q49. Lava Chuar Canyon locality, Tanner Member, Galeros Formation, Chuar Group, Grand Canyon (Fig. 21.1).

Diagnosis

Organic-walled vesicle with sets of parallel, rounded ridges and valleys approximately equal in width and spaced ~1 µm apart from the crest of one ridge to the next. Ridges darker in transmitted light than are valleys. Surface may have several sets of ridges, with sets oriented at angles to each other; each set typically consists of two to seven ridges.

Occurrence

Neoproterozoic Alinya Formation, Giles 1 drill core, and Browne Formation, Kanpa 1A drill hole, Officer Basin, Australia (Cotter, Reference Cotter1999; Riedman and Porter, Reference Riedman and Porter2016); Mesoproterozoic Conselheiro Mata Group (well 1-PSB-13-MG), Espinhaço Supergroup, Brazil (Simonetti and Fairchild, Reference Simonetti and Fairchild2000).

Description

Organic-walled vesicles 25 to 45 µm in diameter (mean=32 µm, SD=5, N=12), with sets of two to seven parallel ridges. Ridges are spaced ~1 µm apart. Ridges may be up to 4 to 9 µm in length and are bounded—though not sharply—by other sets of ridges that are oriented at an angle to them (measured angles range from ~40° to 90°.) Ridges in contiguous ridge sets may be joined to form a ‘V’ (Fig. 21.1b, 21.2a). Under transmitted light, ridges and valleys can be distinguished by their different opacity: valleys are lighter in color (Fig. 21.1, 21.4a, 21.6). The ridges and valleys are sinusoidal in cross section and reflect variations in wall thickness; they do not merely reflect wrinkling of a uniformly thick wall (Fig. 21.7a). An outer envelope is present in some specimens. No excystment structures have been observed.

Etymology

Named in honor of Carol Dehler, a geologist who has made significant contributions to Precambrian geology through her studies of the Chuar Group and its correlatives, and who was a cheerful, generous, and loyal field companion and colleague to SMP during the collection and study of these fossils.

Remarks

Volleyballia dehlerae differs from Valeria lophostriata in that the ridges in the latter form concentric circles and are expressed on the inner surface of the vesicle wall (Javaux et al., Reference Javaux, Knoll and Walter2004). It differs from Karenagare alinyaensis Riedman and Porter, Reference Riedman and Porter2016 in having more closely spaced ridges (~1 µm from crest to crest in V. dehlerae vs. ~3 µm in K. alinyaensis) and having short (4 to 9 µm) ‘ridge sets.’ In addition, the ridges in K. alinyaensis do not appear to reflect variations in vesicle wall thickness but rather ripples in a wall of constant thickness (Riedman and Porter, Reference Riedman and Porter2016).

Striasphera radiata Liu in Gao et al., Reference Gao, Xing and Liu1995 and Striasphaera irregulari Liu in Gao et al., Reference Gao, Xing and Liu1995 from the Neoproterozoic Qinggouzi Formation, Hunjiang area, Jilin Province, China, also exhibit ridge-like ornaments on the vesicle (Gao et al., Reference Gao, Xing and Liu1995). However, while it is difficult to confirm this with the images provided (Gao et al., Reference Gao, Xing and Liu1995, pl. 2, figs. 10, 11), S. radiata appears to have a more complex topography than V. dehlerae, as suggested by the presence of rounded processes visible on the outer edges. S. irregulari differs from V. dehlerae in having wider valleys (2 to 3 µm), sets of parallel ridges that are greater in number, and a flange-like structure consisting of eleven ridges radiating away from the edge of the fossil (on the upper left of the fossil, pl. 2, fig. 12).

Unnamed form A

Figure 22.1

Figure 22 Unnamed forms A–C. (1, 1a, 1b, 1c) Unnamed form A, UCMP 36093c, SP14-63-14. (1a) Note dimpling on vesicle’s inner surface where processes arise; (1b) closeup showing sinuous fibers (black arrows) extending horizontally along vesicle surface; (1c) closeup showing ropy texture on vesicle surface between processes; black arrow points to broken process showing solid construction. (2, 3, 3a) Unnamed form B. (2) UCMP 36086d, SP14-63-12; (3, 3a) UCMP 36085c, SP14-63-12. (4) Unnamed form C, UCMP 36083k, SP14-63-11.

Description

A single vesicle with numerous (2 to 3 per µm²) blunt-tipped conical processes 0.7 to 1.1 µm in length and 0.3 to 0.5 µm in width at their base. The surface of the vesicle between the processes has a ropy texture, as if it is composed of thin fibers that have been fused together and are now barely distinguishable (Fig. 22.1c). The inner surface of the vesicle is dimpled where the processes arise (Fig. 22.1a); the processes are thus partly hollow, but occasional broken processes (Fig. 22.1c) reveal solid construction distally. Vesicle is 33 µm in diameter and covered by a thin, smooth outer envelope that closely replicates the underlying vesicle surface resulting in a verrucate appearance. A few thin sinuous fibers, 0.2 µm in width and up to 2.5 µm in length, extend horizontally along the vesicle surface (Fig. 22.1b). Fibers appear to arise from the vesicle surface and are perhaps related to the subtle ropy texture observed on the interprocess vesicle surface.

Remarks

Unlike Lanulatisphaera laufeldii, the cone-like processes observed in this specimen are not formed from distal fusion of several fibers that arise separately from the vesicle surface. There is also no evidence for dimpling on the inner vesicle surface of L. laufeldii (Fig. 10.1). However, the presence of fibers similar in width to those observed in L. laufeldii may indicate a relationship between these two, perhaps phylogenetic or ontogenetic.

A specimen from the Jupiter Member (sample SP12-63-30) may be related to the specimen described in the preceding. Unfortunately, it is poorly preserved, and the outer envelope obscures most of the details of the inner vesicle. The specimen is much larger in size (63 µm diameter) with longer (4 µm) and wider processes (1 µm at their base), but like the specimen described, the processes appear to be hollow, at least in their basal part.

Unnamed form B

Figure 22.2, 22.3

Description

Organic-walled vesicles 23 to 26 µm in diameter (N=2), with an outer surface that exhibits numerous grooves, ~3 µm long and 0.6 to 0.9 µm wide. Grooves appear to be formed by flattening of elongate pillow-like elements, judging from the wrinkled and folded appearance of the layer that forms the outer surface of the wall.

Remarks

These specimens bear some similarities with Volleyballia dehlerae and with furrowed specimens of Lanulatisphaera laufeldii (Fig. 10.6, 10.7). However, the similarities appear to be superficial: the specimens lack the sets of wave-like ridges and valleys characteristic of V. dehlerae and the filamentous processes characteristic of L. laufeldii. Instead it seems likely these specimens represent a new species, but because of the limited material available, they are kept here in open nomenclature.

Unnamed form C

Figure 22.4

Description

Smooth, organic-walled spheroidal vesicles 48 to 58 µm in diameter (N=2) with a darkened circular spot ~10 µm in diameter on the vesicle wall. One specimen exhibits a very thin outer envelope (Fig. 22.4).

Material examined

Two specimens (samples SP14-63-11 and -17).

Remarks

These specimens differ from Leiosphaeridia Eisenack, 1958b in having an outer envelope around the vesicle. In addition, they exhibit darkened spots on the vesicle wall, which may be original biological features of the vesicle or which may represent contracted protoplast that was fused to the wall during late diagenesis (Pang et al., Reference Pang, Tang, Schiffbauer, Yao, Yuan, Wan, Chen, Ou and Xiao2013). (That these spots are now part of the wall is suggested by the fact that cracks in the vesicle wall also run through the spot and that both are in the same focal plane; Fig. 22.4.) Given the uncertainty in the origin of the dark spot, we have refrained from placing these specimens in either the double-walled form Pterospermopsimorpha (Timofeev, Reference Timofeev1966) emend. Mikhailova and Jankauskas in Jankauskas et al., Reference Jankauskas, Mikhailova and Hermann1989.

Unnamed form D

Figure 23.2

Figure 23 (1) Navifusa majensis Pyatiletov, Reference Pyatiletov1980, UCMP 36094d, SP14-63-14. (2, 2a, 2b) Unnamed form D, UCMP 36072c, SP12-63-30.

Description

Vesicles 28 to 30 µm in diameter, with walls bearing polygonal pillows, now compressed, typically square in shape, though with rounded edges. The pillows are 3 to 4 µm in width and are bordered by thin furrows. Structure of the vesicle not discernible under transmitted light microscopy (Fig. 23.2b).

Remarks

It is not clear whether the overlapping contact of the two specimens reflects biological or accidental circumstances; it is assumed here to be accidental and that these are two distinct specimens.

Unnamed form E

Figure 24.1–24.3

Figure 24 Unnamed form E. (1, 1a, 1b) UCMP 36079c, SP14-63-11. (2, 2a, 2b) UCMP 36082c, SP14-63-11. (3, 3a, 3b) UCMP 36079d, SP14-63-11. Specimen in (3) may, alternatively, be a form of C. revelata.

Description

Organic-walled vesicles 48 to 134 µm in diameter (mean=85 µm, SD=35 µm, N=5) that exhibit a ropy texture on their surface that appears to result from the flattening of originally convex elements roughly ~3 to 6 µm in diameter. These flattened elements appear to overlie additional ropy structures, which may reflect flattening of one or several underlying layers. Wall appears mottled in transmitted light (Fig. 24.1b, 24.2b, 24.3b).

Remarks

Although these five specimens are highly variable in size, they do share the same ropy appearance under SEM and mottled appearance under TLM. Whether some of these might represent degraded end member forms of Culcitulisphaera revelata (with unusually large pillow elements; Fig. 24.3a), much larger specimens of Unnamed form D, or a new species cannot be determined from present material.