Type species

Siphonophycus kestron Schopf, Reference Schopf1968 (holotype: Paleobotany Collection Harvard University no. 58469, stage coordinates 33.6 × 101.4) from the black chert facies in the middle third of the late Precambrian Bitter Springs Formation, exposed on the south slope of the ridge about 1 mile north of Ross River Tourist Camp (Love's Creek Homestead), 40 miles northeast of Alice Springs, Northern Territory, Australia, by original designation.

Other species

Siphonophycus thulenema Butterfield in Butterfield et al., Reference Butterfield, Knoll and Swett1994; Siphonophycus septatum (Schopf, Reference Schopf1968); Siphonophycus robustum (Schopf, Reference Schopf1968); Siphonophycus typicum (Hermann, Reference Hermann and Timfeev1974); Siphonophycus kestron Schopf, Reference Schopf1968; Siphonophycus solidum (Golub, Reference Golub and Sokolov1979); Siphonophycus punctatum Maithy, Reference Maithy1975; and Siphonophycus gigas Tang et al., Reference Tang, Pang, Xiao, Yuan, Ou and Wan2013.

Original diagnosis by Schopf (Reference Schopf1968)

“Thallus broad, tubular, nonseptate, unbranched, commonly quite long, finely rugose in surface texture. Thallus cylindrical, somewhat tapered toward apices, solitary, straight to slightly bent, up to 180 μm long (incomplete specimen), occasionally folded and distorted. Apices apparently capitate, more-or-less constricted adjacent to expanded, broadly conical, bluntly pointed terminus. Thallus quite broad, 8.3–15.00 μm wide, commonly about 12.5 μm wide (based on five specimens), ornamented and ringed by finely punctate surficial ridges regularly spaced out 2/3 μm apart. Reproductive structures unknown.”

Emended diagnosis by Knoll et al. (Reference Knoll, Swett and Mark1991)

“Tubular, filamentous microfossils, nonseptate and unbranched, with little or no tapering toward filament termini; tubes truncated and open at ends or with closed, more or less hemispherical terminations; walls typically preserved as chagrenate to finely reticulate organic matter, but may be preserved as carbonate rinds.”

Remarks

The genus Siphonophycus is characterized by smooth and thin wall filaments without ornamentation. The taxon is traditionally interpreted as representing empty sheaths of filamentous cyanobacteria, but because of simple morphology, it could include a range of bacterial and eukaryotic organisms (Butterfield et al., Reference Butterfield, Knoll and Swett1994). Although it is here placed under cyanobacteria, we recognize that Siphonophycus is a form taxon, and several other genera of filamentous microfossils (e.g., Eomycetopsis, Tenuofilum, and Leiotrichoides) are regarded as synonyms of Siphonophycus (Knoll et al., Reference Knoll, Swett and Mark1991).

Holotype

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

Original diagnosis by Schopf (Reference Schopf1968)

“Filaments commonly solitary, occasionally in groups of a few entangled filaments, rarely showing plectenchymatous organization. Lateral walls approximately1/3–3/4 μ thick, markedly coriaceous, coarsely and irregularly granular in surface texture. Filaments up to 135 μ long (incomplete filament), more-or-less regularly cylindrical with a variance in diameter of less than 0.8 μ from the widest to the most narrow portion of the filament; 2.8–4.2 μ in diameter with an average width (20 filaments measured of 3.5 μ). Septate portions of filament vary in length, commonly less than 25 μ long, with filaments commonly constricted or overlapping at the septa; overlapping portions commonly with rounded ends. Reproductive structures unknown.”

Emended diagnosis by Knoll and Golubic (Reference Knoll and Golubic1979)

“Filaments cylindrical; unbranched; tubular (nonseptate); bent, sinuous and tortuous; partially flattened, circular to elliptical in cross section; intertwined to form more or less dense meshworks; long. Surface coarsely to irregularly granular in texture. Occasional cylindrical and evenly spaced inclusions, homogeneously filled with fine-grained carbonaceous matter and centrally located in the ‘bore’ of the tube. Filaments tubular with average diameters expressed as mean ± standard deviation 2.95 ±μm (range 2.0–4.4, n = 60). Occasional long cylindrical inclusions, 1.09 ± 0.36 μm (n = 8) in diameter, 3–4 μm long located centrally within tubular filaments.”

Emended diagnosis by Knoll et al. (Reference Knoll, Germs, Tankard and Welsink2020)

“A species of Siphonophycus with tubes 2–4 μm in cross-sectional diameter.”

Occurrence in the studied section

MP2985, MP2995, MP3040, MP3708, MP3709, and MP3710.

Illustrated specimen

CP960 (3 μm in diameter).

Remarks

Filamentous microfossils from the Sete Lagoas Formation are scarce and restricted to Siphonophycus robustum (Schopf, Reference Schopf1968).

Type species

Ghoshia bifurcata Mandal and Maithy in Mandal et al., Reference Mandal, Maithy, Barman and Verma1984.

Original diagnosis presented by Mandal and Maithy in Mandal et al. (Reference Mandal, Maithy, Barman and Verma1984)

“Thallus heterotrichous, erect filaments arising from basal horizontally creeping thallus, densely packed, truly laterally branched, with cells in one or two series; sheath absent; reproduction not observed.”

Type specimens

Holotype: CP916. Paratypes: CP919 and CP920. Specimens are housed in the Research Collection, Museum of Geosciences, Institute of Geosciences, University of Brasília, Federal District, Brazil.

Diagnosis

A species of Ghoshia characterized by spherical to doliform cells that are 3–10 μm in diameter. Cells are organized to form uniserial chains that branch irregularly.

Occurrence in the studied section

MP2980, MP3013, MP3015, MP3040, MP3710, MP3714, MP3718, MP3723, and MP3724.

Description

Uniserial cell chains that branch irregularly. Cells are spherical (Fig. 4.1), doliform (Fig. 4.2–4.6, 4.9), or polyhedral (Fig. 4.7), with smooth cell walls. Side branches arise more or less perpendicularly to the main branches. Cells at the branching points are often polyhedral (Fig. 4.7). Cells 3–10 μm in diameter. Deformation folds, likely resulting from compression, are present in some cells (Fig. 4.2, 4.7, 4.8).

Etymology

In reference to the Municipality of Januária, Minas Gerais State, Brazil.

Illustrated specimens

CP916, CP919, and CP920.

Remarks

The Sete Lagoas specimens are somewhat similar to Arctacellularia German in Timofeev et al., Reference Timofeev, Hermann and Mikhailova1976 in their uniserial filaments consisting of spherical, doliform, and polyhedral cells. However, unlike the Sete Lagoas specimens, Arctacellularia does not branch. The Sete Lagoas specimens are also similar to the Devonian cyanobacteria Langiella Croft and George, Reference Croft and George1959, Kidstoniella Croft and George, Reference Croft and George1959, and Rhyniella Croft and George, Reference Croft and George1959 in having branching filaments. However, these Devonian genera can be distinguished by the presence of morphologically differentiated heterocysts and akinetes or by the presence of a sheath (Croft and George, Reference Croft and George1959). The Sete Lagoas specimens are best placed in the genus Ghoshia, which is characterized by branching uniserial filaments consisting of largely undifferentiated cells. The new species proposed here, Ghoshia januarensis, resembles Ghoshia bifurcata Mandal and Maithy in Mandal et al., Reference Mandal, Maithy, Barman and Verma1984 in cell size but differs in its more variable cell shape; Ghoshia januarensis has spherical, doliform, and polyhedral cells, whereas Ghoshia bifurcata is said to have “drum-shaped to rectangular” cells (Mandal et al., Reference Mandal, Maithy, Barman and Verma1984). In addition, some specimens of Ghoshia bifurcata (including the holotype; Mandal et al., Reference Mandal, Maithy, Barman and Verma1984, pl. 4, fig. 30) seem to have cell aggregates that are not uniserially organized.

A specimen from the Sete Lagoas Formation in the Januária area illustrated as “fossil filaments consisting of aligned rounded cells” (Perrella Júnior et al., Reference Perrella Júnior, Uhlein, Uhlein, Sial, Pedrosa-Soares and Lima2017, fig. 7H) shares the same characteristics of Ghoshia januarensis, including uniserial and branching filaments consisting of spherical cells. Thus, this specimen is here identified as Ghoshia januarensis. It is important to point out that the specimen illustrated in Perrella Júnior et al. (Reference Perrella Júnior, Uhlein, Uhlein, Sial, Pedrosa-Soares and Lima2017) was observed in a petrographic thin section, ruling out the possibility of modern contamination.

Raman spectra of the analyzed microfossils (Fig. 5) display well-developed D₁ and D₂ bands positioned at 1,350 cm^–1 and 1,620 cm^–1, respectively. These characteristics are typical of organic matter spectra (Kouketsu et al., Reference Kouketsu, Mizukami, Mori, Endo, Aoya, Hara, Nakamura and Wallis2014). The Raman data show that the four analyzed specimens of Ghoshia januarensis, including the holotype, are distinct from other organic-walled microfossils from the Sete Lagoas Formation (Fig. 5). Relative to other organic-walled microfossils from the Sete Lagoas Formation, Ghoshia januarensis specimens exhibit broader peaks (Fig. 5.1). PCA analysis of Raman parameters also shows that Ghoshia januarensis specimens are separate from other organic-walled microfossils from the Sete Lagoas Formation (Fig. 5.2). Therefore, it is possible that specimens of Ghoshia januarensis have different thermal history from other organic-walled microfossils in the Sete Lagoas Formation, indicating that the former could be contaminations. However, the three specimens of Ghoshia januarensis that were analyzed for Raman spectroscopy in Fig. 5.2 overlap with the other organic-walled microfossils largely along the second PCA axis; the difference is mainly along the primary PCA axis. A similar situation is found in the four specimens of Leiosphaeridia minutissima that were analyzed for Raman spectroscopy (labeled as A, B, G, and H in Fig. 5.2): they exhibit a limited range and overlap with other organic-walled microfossils from the Sete Lagoas Formation along the primary PCA axis, but two specimens (labeled A and B in Fig. 5.2) are distinct from all other specimens along the secondary PCA axis. Although subtle differences in carbonaceous material Raman characteristics could be taken as evidence for different degrees of thermal maturation (Kouketsu et al., Reference Kouketsu, Mizukami, Mori, Endo, Aoya, Hara, Nakamura and Wallis2014), recent studies show that such differences can result from differences in organic precursors (Qu et al., Reference Qu, Engdahl, Zhu, Vajda and McLoughlin2015; Pang et al., Reference Pang, Tang, Wu, Li, Chen, Wan, Yuan, Bodnar and Xiao2020). Considering that Ghoshia januarensis specimens showed no fluorescence as would modern organic contaminations, and that Ghoshia januarensis has been found in a petrographic thin section of the Sete Lagoas Formation (Perrella Júnior et al., Reference Perrella Júnior, Uhlein, Uhlein, Sial, Pedrosa-Soares and Lima2017), we conclude that Ghoshia januarensis is indigenous to the Sete Lagoas Formation.

Figure 5.

Raman spectroscopic data of organic-walled microfossils and amorphous organic matter from the Sete Lagoas Formation at the Barreiro section. (1) Baseline-corrected and fitted Raman spectra. Legends are shown in Figure 5.2. Note that Raman spectra of Ghoshia januarensis (J from holotype and I, K from paratypes) have broader peaks of carbonaceous matter around 1,350 cm^–1 and 1,600 cm^–1 relative to other Sete Lagoas organic-walled microfossils. (2) Principal component analysis of deconvolved Raman data. Samples: A–B and J, CP916; C–D, CP917; E, I, K, CP920; F, H, MP3728; G, MP3723.

Type species

Leiosphaeridia baltica Eisenack, 1958 (in Eisenack, Reference Eisenack1958b).

Other species

Fensome et al. (Reference Fensome, Williams, Bars, Freeman and Hill1990) revised all Leiosphaeridia species and listed 167 valid species.

Original diagnosis presented by Eisenack (Reference Eisenack1958b) in German

“Hohlkugelförmige, dünnwandige und aus einer sehr widerstandsfähigen, hellgelb bis dunkelrotbraun durchscheinenden organischen Substanz bestehende Organismenreste, die oft in scheibenförmig zusammengepreßtem Zustande oder auch unregelmäßig verfaltet überliefert sein können. Wand, auch in erwachsenem Zustande, stets ohne Wandporen (Unterschied zu Tasmanites). Pylome vorhanden.”

Translation of original diagnosis presented by Eisenack (Reference Eisenack1958b)

Hollow spherical, thin-walled organism residues consisting of a very resistant, light yellow to dark red-brown translucent, organic substance, which can often be preserved as a disc-shaped compressed state or an irregularly folded structure. Wall, even when fully grown, always without wall pores (in contrast to Tasmanites). Pylome present.

Emended diagnosis by Downie and Sarjeant (Reference Downie and Sarjeant1963)

“Spherical to ellipsoidal bodies without processes, often collapsed or folded, with or without pylomes. Walls granular, punctate or unornamented, thin. Without divisions into fields and without transverse or longitudinal furrows or girdles.”

Emended diagnosis by Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) in Russian

“Сфероидальные оболочки с гладкой, точеечной или зеррнистой поверхиостью размером от 2–3 до 750 мкм. Толщина стенки от долей микрометра до 3–10 мкм. В ископаемом состоянии сплющены и осложнены складками смятия различной формы и размеров.”

Translation of emended diagnosis by Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989)

Spheroidal vesicle with a smooth, punctate, or granular surface ranging in size from 2–3 to 750 μm. The wall thickness varies from fractions of a micrometer to 3–10 μm. The specimens are flattened and can have compressional folds of various shapes and sizes.

Remarks

A great number of species of the genus Leiosphaeridia have been reported from the Proterozoic, and many of them have very long stratigraphic ranges, e.g., from the Paleoproterozoic to the Mesozoic (Lamb et al., Reference Lamb, Awramik, Chapman and Zhu2009). There are even reports of Leiosphaeridia species from the Miocene (Hannah et al., Reference Hannah, Wilson and Wrenn2000). Because of its simple morphologies, the genus Leiosphaeridia is regarded as a form taxon with diverse phylogenetic affinities, and it is classified in the Acritarcha (Jankauskas et al., Reference Jankauskas, Mikhailova and German1989; Grey, Reference Grey2005; Sergeev and Schopf, Reference Sergeev and Schopf2010), although Sergeev and Schopf (Reference Sergeev and Schopf2010) consider this taxon as belonging to the Kingdom Protista, a proposition followed here. It is important to point out that some authors relate Leiosphaeridia species to chlorophyceaens (Moczydlowska et al., Reference Moczydlowska, Landing, Zang and Palacios2011; Moczydłowska, Reference Moczydłowska2016). Downie and Sarjeant (Reference Downie and Sarjeant1963) emended the diagnosis of the genus Leiosphaeridia to exclude the reference of the vesicle color since it could reflect diagenetic features. Moreover, the maceration protocol could affect the color of organic vesicles due to the use of oxidizing solutions. Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) specified that the diameter of the vesicle of Leisophaeridia species ranges from 2–3 to 750 μm. Furthermore, Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) divided the smooth-walled Leiosphaeridia species into four species according to vesicle diameter and wall thickness, a form-taxonomical scheme followed in the present work. Butterfield et al. (Reference Butterfield, Knoll and Swett1994) suggested that Leiosphaeridia should be restricted to spheroidal fossils with vesicle walls less than 2 μm thick so that it can be differentiated from Chuaria circularis Walcott, Reference Walcott1899, which has thicker vesicle walls (2–3 μm single-wall thickness).

Type material

Naumova (Reference Naumova1949) did not designate a holotype for Leiotriletes crassus. Subsequently, Jankauskas in Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) designated one specimen of Leiotriletes crassus published by Naumova (Reference Naumova1949) as a “holotype” (Naumova, Reference Naumova1949, pl. 1, fig. 3). In addition, he designated another specimen from a different locality and a different stratigraphic unit as a “lectotype” (Jankauskas et al., Reference Jankauskas, Mikhailova and German1989, LitNIGRI, N 16-800-2942/9, specimen 2, table 9, fig. 5). By so doing, the selection of a holotype by Jankauskas can, according to the International Code of Nomenclature for Algae, Fungi, and Plants, be taken as the designation of a lectotype (Turland et al., Reference Turland, Wiersema, Barrie, Greuter and Hawksworth2018). In addition, the specimen designated by Jankauskas as a “lectotype” should be regarded as a neotype. According to the same code, a lectotype always takes precedence over a neotype. However, the lectotype designated by Jankauskas was a specimen of Leiotriletes simplicissimus (Naumova, Reference Naumova1949), a species he synonymized with a different species of Leiosphaeridia, Leiosphaeridia minutissima. Thus, the lectotype designated by Jankauskas is not valid, and the neotype designated by Jankauskas in Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) is here considered the valid type specimen of Leiosphaeridia crassa.

Original diagnosis presented by Naumova (Reference Naumova1949) in Russian

“В очертании спора округлой или округло-овальной формы. Поверхность экзины гладкая, экзина очень толстая и плотная. Форма имеет складки смятия, щель разверзания, простая. Широко распространена в нижнем кембрии Прибалтики.”

Translation of original diagnosis presented by Naumova (Reference Naumova1949)

In outline, the spore is round or round–oval. The surface of the exine is smooth, very thick, and dense. The form has compressional folds, an opening gap, and is simple. Widespread in the lower Cambrian of the Baltic.

Emended diagnosis by Javaux and Knoll (Reference Javaux and Knoll2017) and Knoll et al. (Reference Knoll, Germs, Tankard and Welsink2020)

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

Occurrence in the studied section

Fourteen specimens were recovered. They range from ~18 to ~62 μm in diameter: MP3719 and MP3720.

Illustrated specimen

CP964 (diameter ~27 μm).

Remarks

Leiotriletes crassus Naumova, Reference Naumova1949 was originally published with only a description, without a diagnosis. Although the International Code of Nomenclature for Algae, Fungi, and Plants states that either a description or a diagnosis is sufficient for the valid publication of a name (Turland et al., Reference Turland, Wiersema, Barrie, Greuter and Hawksworth2018, Art. 38.1), it is strongly recommended that both the diagnosis and description be presented when describing a new species (Hassemer et al., Reference Hassemer, Prado and Baldini2020). Later, Jankauskas in Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) reviewed some species of Leiosphaeridia and transferred Leiotriletes crassus Naumova, Reference Naumova1949 to the genus Leiosphaeridia. When Leiotriletes crassus was transferred to the genus Leiosphaerida, the species epithet was changed to crassa, so the gender of the epithet agrees with the gender of the genus name. Thus, this species became Leiosphaeridia crassa (Naumova, Reference Naumova1949) Jankauskas in Jankauskas et al., Reference Jankauskas, Mikhailova and German1989. In addition, Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) did not include in their synonym list the species Leiopsophosphaera crassa Pykhova, Reference Pykhova1973. Finally, Fensome et al. (Reference Fensome, Williams, Bars, Freeman and Hill1990), also in a work of taxonomic revision, transferred Leiopsophosphaera crassa Pykhova, Reference Pykhova1973 to Leiosphaeridia crassa (Pykhova, Reference Pykhova1973). However, Fensome et al. (Reference Fensome, Williams, Bars, Freeman and Hill1990) did not consider the study of Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) and regarded Leiotriletes crassus Naumova, Reference Naumova1949 as taxonomically uncertain (Grey, Reference Grey2005). Thus, Leiosphaeridia crassa (Pykhova, Reference Pykhova1973) is a junior homonym of Leiosphaeridia crassa (Naumova, Reference Naumova1949) Jankauskas in Jankauskas et al., Reference Jankauskas, Mikhailova and German1989. Nonetheless, Leiopsophosphaera crassa Pykhova, Reference Pykhova1973 is considered by several authors (Yin and Guan, Reference Yin and Guan1999; Grey, Reference Grey2005) as a synonym of Leiosphaeridia crassa (Naumova, Reference Naumova1949), a synonymy followed in this study. Leiosphaeridia crassa differs from Leiosphaeridia minutissima in its thicker vesicle wall, and it differs from Leiosphaeridia tenuissima and Leiosphaeridia jacutica in vesicle size (Jankauskas et al., Reference Jankauskas, Mikhailova and German1989).

Holotype

IGD Russian Academy of Sciences no. 451/1, from upper Riphean, Lakhanda Group, Neryuen Formation, Siberia (Timofeev, Reference Timofeev1966, pl. 7, fig. 2).

Diagnosis by Javaux and Knoll (Reference Javaux and Knoll2017) and Knoll et al. (Reference Knoll, Germs, Tankard and Welsink2020)

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

Occurrence in studied section

Four specimens were recovered. They range from ~74 to ~98 μm in diameter: MP2990, MP3719, and MP3714.

Original description by Timofeev (Reference Timofeev1966) in Russian

“Оболочки диаметром 150–250 мк, сферические, толстые, однослойные, с поверхностью от гладкой до грубошагреневой, с резко очерченными, крупными, серповидными, иногда угловатымц складками. Цвет темно-желтый, желто-коричневый.”

Translation of original description by Timofeev (Reference Timofeev1966)

The vesicles are 150–250 microns in diameter, spherical, thick, single-layered, with a smooth to coarse shagreen surface that bears sharply defined, large, crescent-shaped, sometimes angular folds. Color dark yellow, yellow-brown.

Illustrated specimen

CP913 (diameter ~81 μm).

Remarks

Timofeev (Reference Timofeev1966) described the new species Kildinella jacutica Timofeev, Reference Timofeev1966 and designated a holotype with the description of this species, but no diagnosis was provided. Later, Mikhailova and Jankauskas in Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) proposed that Kildinella jacutica should be transferred to Leiosphaeridia jacutica (Timofeev, Reference Timofeev1966). They also designated a neotype for Leiosphaeridia jacutica. This neotype is not valid since Timofeev (Reference Timofeev1966) had designated a holotype in its publication, and there is no report of the loss of this holotype. Leiosphaeridia jacutica differs only by the larger size compared with Leiosphaeridia crassa (Jankauskas et al., Reference Jankauskas, Mikhailova and German1989). The specimen illustrated by Tang et al. (Reference Tang, Hughes, McKenzie, Myrow and Xiao2017, fig. 3) may not be Leiosphaeridia crassa but Leiosphaeridia jacutica because its diameter is around 90 μm. Leiosphaeridia jacutica differs from Bambuites erichsenii in its sphaeromorphic vesicle without processes.

Type material

Naumova (Reference Naumova1949) did not designate a holotype for Leiotriletes minutissimus. Afterward, Jankauskas in Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) designated one of the specimens published by Naumova (Reference Naumova1949, pl. 1, fig. 1) as the “holotype”. In addition, he designated another specimen from a different locality and a different stratigraphic unit as a “lectotype” (Jankauskas et al., Reference Jankauskas, Mikhailova and German1989, LitNIGRI, N 16-800-2942/9, table 9, fig. 1). According to the International Code of Nomenclature for Algae, Fungi, and Plants (Turland et al., Reference Turland, Wiersema, Barrie, Greuter and Hawksworth2018), the “holotype” selected by Jankauskas should be regarded as a lectotype and the “lectotype” regarded as a neotype. According to the same code, a lectotype takes precedence over a neotype. Thus, the lectotype designated by Jankauskas in Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) (Naumova, Reference Naumova1949, pl. 1, fig. 1) is the valid type specimen of Leiosphaeridia minutissima.

Diagnosis presented by Javaux and Knoll (Reference Javaux and Knoll2017)

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

Emended diagnosis presented by Knoll et al. (Reference Knoll, Germs, Tankard and Welsink2020)

“A species of Leiosphaeridia characterized by thin, smooth walls with sinuous folds and a modal diameter less than 70 μm.”

Occurrence in studied section

A total of 359 specimens were recovered. They range from ~4.4 to ~68.2 μm in diameter: MP3719, MP2977, MP2979, MP2980, MP2983, MP2985, MP2986, MP2987, MP2988, MP2992, MP2993, MP2994, MP2995, MP2998, MP2999, MP 3002, MP 3004, MP 3005, MP 3006, MP 3007, MP 3011, MP 3012, MP 3013, MP 3015, MP 3016, MP3028, MP 3030, MP3031, MP3033, MP3034, MP3035, MP3036, MP3705, MP3707, MP3708, MP3709, MP3710, MP3712, MP3713, MP3714, MP3715, MP3716, MP3719, and MP3720.

Description presented by Naumova (Reference Naumova1949) in Russian

“Очертание споры округлое. Экзина очень тонкая, прозрачная, наблюдаются многочисленные складки смятия. Поверхность экзины гладкая. Щель разверзания трехлучевая, простая, плохо различимая нз-за складок смятия.”

Translation of description presented by Naumova (Reference Naumova1949)

The outline of the vesicle is round. The exine is very thin, transparent, with numerous compressional folds. The surface of the exine is smooth. The opening slit is three-beam, simple, poorly distinguishable due to the compressional folds.

Illustrated specimens

CP918 (diameter ~32 μm), CP962 (diameters 32~ μm and ~39 μm), CP963 (diameter ~38 μm), and CP964 (diameter ~45 μm).

Remarks

The basionym of Leiosphaeridia minutissima (Naumova, Reference Naumova1949) is Leiotriletes minutissimus Naumova, Reference Naumova1949. As for Leiotriletes crassus, Naumova (Reference Naumova1949) did not present a diagnosis for this species but provided a detailed description. Subsequently, Jankauskas in Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) transferred this species to Leiosphaeridia minutissima (Naumova, Reference Naumova1949) without presenting a diagnosis. When Leiotriletes minutissimus was transferred to the genus Leiosphaerida, the epithet was changed to minutissima, so the gender of the epithet agrees with the gender of the genus name. The first formal diagnosis for Leiosphaeridia minutissima was presented by Javaux and Knoll (Reference Javaux and Knoll2017), emended later by Knoll et al. (Reference Knoll, Germs, Tankard and Welsink2020).

Holotype

Preparation A3, 3 number 4, from the Dictyonema shales of the Ordovician Baltic, Nikolskaya on the Tossna, southeast Leningrad (Eisenack, Reference Eisenack1958a, pl. 1, fig. 2).

Original diagnosis presented by Eisenack (Reference Eisenack1958a) in Germany

“Wand äußerst dünn und zart, glasklar durchscheinend, ohne Wandporen; nur in flachgedrücktem Zustand in Form von fast kreisrunden Scheibchen überliefert. Pylome nicht beobachtet. Ø um rd 100 μm schwankend.”

Translation of original diagnosis presented by Eisenack (Reference Eisenack1958a)

Wall extremely thin and delicate, crystalline translucent, without wall pores; only preserved in the flattened state in the form of almost circular disks. Pyloma not observed. Size around 100 μ.

Emended diagnosis by Javaux and Knoll (Reference Javaux and Knoll2017)

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

Occurrence in the studied section

Fourteen specimens were recovered. They range from ~72 to ~126 μm in diameter: MP3002, MP3007, MP2994, MP3707, MP3709, MP3013, MP3714, MP3719, and MP3720.

Illustrated materials

CP914 (diameters: ~81 μm in Fig. 3.9 and ~86 μm in Fig. 3.13).

Remarks

Both Leiosphaeridia tenuissima Eisenack, 1958 and Leiosphaeridia minutissima (Naumova, Reference Naumova1949,) are simple sphaeromorphs and have a thin and translucent wall less than 0.5 μm thick. However, Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989) differentiated them on the basis of vesicle size, defining specimens smaller than 70 μm in diameter as Leiosphaeridia minutissima and specimens larger than 70 μm as Leiosphaeridia tenuissima. The specimen illustrated by Sergeev et al. (Reference Sergeev, Vorob'eva and Petrov2017a, fig. 3.13) as Leiosphaeridia minutissima is better identified as Leiosphaeridia tenuissima due to its greatest diameter of about 105 μm.

Type species

Germinosphaera bispinosa Mikhailova, Reference Mikhailova and Sokolov1986.

Other species

Germinosphaera guttaformis Mikhailova in Jankauskas et al., Reference Jankauskas, Mikhailova and German1989; Germinosphaera alveolata Miao et al. (Reference Miao, Moczydłowska, Zhu and Zhu2019).

Original diagnosis presented by Mikhailova (Reference Mikhailova and Sokolov1986) in Russian

“Оболочки округлые, округло-овальные, плотные, толстые, гладкие или шагреневые, проросшие. Отростки, которые могут ветвиться, наблюдаются на одном или двух поолюсах.”

Translation of original diagnosis presented by Mikhailova (Reference Mikhailova and Sokolov1986)

The shells are round or round-oval, dense, thick, smooth or shagreen, sprouted. Processes are observed at one or two poles.

Emended diagnosis by Butterfield et al. (Reference Butterfield, Knoll and Swett1994)

“Spheroidal vesicles with 1–6 open-ended, tubular, and occasionally branched processes that communicate freely with the vesicle. Multiple processes usually restricted to a single ‘equatorial’ plane, but otherwise non-uniformly distributed on the vesicle.”

Emended diagnosis by Miao et al. (Reference Miao, Moczydłowska, Zhu and Zhu2019)

“Vesicle spheroidal, teardrop-shaped to slightly irregular outline, having psilate or low relief sculptured alveolar wall surface and bearing a single to multiple processes. Processes are simple tubular or occasionally branching, and open-ended. Processes are distributed [irregularly] on the vesicle wall, if multiple, and may be predominantly, but not exclusively, distributed in the equatorial plane of the vesicle.”

Holotype

Number 882/2 from the Krasnoyarsk region, River Uderei; Upper Riphean, Dashkin Formation (Mikhailova, Reference Mikhailova and Sokolov1986, fig. 6).

Diagnosis by Butterfield in Butterfield et al. (Reference Butterfield, Knoll and Swett1994)

“A species of Germinosphaera with psilate vesicles 13–35 μm in diameter. Processes 2.5–3.5 μm wide and, when multiple, arranged equatorially on the vesicle.”

Emended diagnosis by Miao et al. (Reference Miao, Moczydłowska, Zhu and Zhu2019)

“Spheroidal to slightly elongate or irregular vesicle with one to multiple tubular processes. Vesicle wall psilate. Processes may [be] arranged irregularly or equatorially on the vesicle wall when multiple.”

Occurrence in the studied section

Twenty-three specimens were recovered: MP3036 and MP3714.

Description

Vesicles are 23.4–34.8 μm in diameter, bearing one to two processes. When two processes are present, they are inserted at two opposing ends of the vesicle (Fig. 3.4). Processes typically taper slightly toward their distal end (Fig. 3.4, lower process, 3.8) or are more or less cylindrical (Fig. 3.11). One of the processes in the specimen illustrated in Fig. 3.4 is apparently constricted at the base. However, it is uncertain whether this constriction is a taphonomic feature related to the twisting of the process. Processes are 1–3 μm in maximum diameter and 22.6–123.0 μm in preserved length.

Illustrated material

CP917.

Remarks

Mikhailova (Reference Mikhailova and Sokolov1986) established two species of Germinosphaera, Germinosphaera unispinosa and Germinosphaera bispinosa. Two additional species were published by Jankauskas et al. (Reference Jankauskas, Mikhailova and German1989), Germinosphaera guttaformis Mikhailova in Jankauskas et al., Reference Jankauskas, Mikhailova and German1989 and Germinosphaera tadasii Weiss in Jankauskas et al., Reference Jankauskas, Mikhailova and German1989. These species were distinguished by the number of processes and the psilate versus shagrinate nature of vesicle walls. However, Butterfield et al. (Reference Butterfield, Knoll and Swett1994) considered the possibility that the processes in Germinosphaera represent growth structures in vegetative stages, analogous to the modern xanthophyte Vaucheria. As such, they emended the diagnosis of Germinosphaera and the diagnosis of G. bispinosa, and they synonymized G. unispinosa with G. bispinosa. Miao et al. (Reference Miao, Moczydłowska, Zhu and Zhu2019) further emended the diagnosis of Germinosphaera and considered shagrinate vesicle walls to represent taphonomic alteration. Furthermore, they noted that the vesicle diameters of different species could overlap each other. Thus, they proposed that G. tadasii and G. jankauskasii, which are characterized by shagrinate vesicle walls, were junior synonyms of G. bispinosa. Following Miao et al. (Reference Miao, Moczydłowska, Zhu and Zhu2019), Germinosphaera currently has three species: Germinosphaera bispinosa Mikhailova, Reference Mikhailova and Sokolov1986, Germinosphaera guttaformis Mikhailova in Jankauskas et al., Reference Jankauskas, Mikhailova and German1989, and Germinosphaera alveolata Miao et al., Reference Miao, Moczydłowska, Zhu and Zhu2019.