Type species

Appendisphaera grandis Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993, emend. Moczydłowska, Reference Moczydłowska2005.

Other species

Appendisphaera anguina Grey, Reference Grey2005; A.? brevispina Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; A. clava Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; A. clustera Liu and Moczydłowska, Reference Liu and Moczydłowska2019; A. fragilis Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993; A. heliaca (Liu and Moczydłowska, Reference Liu and Moczydłowska2019) Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021; A.? hemisphaerica Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; A. lemniscata Liu and Moczydłowska, Reference Liu and Moczydłowska2019; A. longispina Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; A. longitubularis (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014) Liu and Moczydłowska, Reference Liu and Moczydłowska2019, an orthographic correction of A. longitubulare as published in Liu and Moczydłowska (Reference Liu and Moczydłowska2019); A. magnifica (Zhang et al., Reference Zhang, Yin, Xiao and Knoll1998) Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; A. setosa Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; A. tabifica Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993; A. tenuis Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993.

Remarks

Several Appendisphaera species published in the literature have been synonymized with existing species or transferred to other genera, hence they are not listed above. Liu and Moczydłowska (Reference Liu and Moczydłowska2019, p. 61) considered Appendisphaera barbata Grey, Reference Grey2005, A. centoreticulata Grey, Reference Grey2005, A. dilutopila (Zang in Zang and Walter, Reference Zang and Walter1992) Grey, Reference Grey2005, and A. minutiforma Grey, Reference Grey2005, as junior synonyms of A. tabifica. They also regarded A. minima Nagovitsin and Faizullin in Nagovitsin et al., Reference Nagovitsin, Faizullin and Yakshin2004, as a junior synonym of A. tenuis, and excluded A. crebra (Zang in Zang and Walter, Reference Zang and Walter1992) Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014, from the genus Appendisphaera. Liu and Moczydłowska (Reference Liu and Moczydłowska2019) indicated that A. magnifica is synonymous with A. grandis, but did not provide any justification; in this paper we follow Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a) and Ouyang et al. (Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021) and regard A. magnifica as a distinct species of Appendisphaera (see discussion under the species A. grandis).

A Doushantuo specimen illustrated in Liu et al. (Reference Liu, Qi, Fan, Guo, Pei, Huang, Cheng, Bian, Liu, Zhao and Zhang2021) as Ericiasphaera magna seems to have hollow rather than solid process (see Liu et al., Reference Liu, Qi, Fan, Guo, Pei, Huang, Cheng, Bian, Liu, Zhao and Zhang2021, fig. 4.5, 4.6), and thus may belong to the genus Appendisphaera. It is somewhat similar to A. setosa or A. tenuis in process density and morphology, particularly the extremely thin processes (~1.0–1.5 μm wide at the base and ~0.3 μm wide above the base).

Appendisphaera clava Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014
Figures 5, 6

Reference Liu, Yin, Chen, Tang and Gao2013

Unnamed (E); Liu et al., fig. 12A, B.

Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a

Appendisphaera clava Liu et al., p. 12, figs. 5.4, 8.1–8.5, 9.1–9.7.

Reference Muscente, Hawkins and Xiao2015

Appendisphaera clava; Muscente et al., fig. 5D.

Reference Ouyang, Zhou, Xiao, Chen and Shao2019

Appendisphaera clava; Ouyang et al., fig. 8G, H (part).

Reference Grazhdankin, Nagovitsin, Golubkova, Karlova, Kochnev, Rogov and Marusin2020

Appendisphaera clava; Grazhdankin et al., fig. 3C.

Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021

Appendisphaera clava; Ouyang et al., fig. 10K, L.

Figure 5. Appendisphaera clava. (1–3) DH-14-67.0-B-2, 20.8 × 111.6, EF-H11-2, VPIGM-4847, rectangle in (1) marks area shown in (2) at a different focal level, arrow in (2) marks area shown in (3) at a different focal level; (4–6) S4-4-F2-7, 3.0 × 139.5, EF-AA39-1, VPIGM-4889, rectangle in (4) marks area shown in (5) at a different focal level and with a slight rotation, arrow in (4) marks area shown in (6) at a different focal level and with a slight rotation; (7, 8) S4-4-F2-5, 23.0 × 107.0, EF-E7-1, VPIGM-4878, arrow in (7) marks area shown in (8) at a different focal level and with a slight rotation. All specimens illustrated in this paper are from the Krol A Formation, Solan, northern India. For each illustrated specimen, the following information is given: thin section number (which is the sample number with a differentiating suffix if multiple thin sections were made from the sample), Olympus BX-51 coordinates, England Finder coordinates, and VPIGM catalog number.

Figure 6. Appendisphaera clava. (1–3) S4-4-F1-4, 17.0 × 124.5, EF-L24-4, VPIGM-4871, rectangle in (1) marks area shown in (2) and (3) at different focal levels; (4, 5) DH-14-67.0-C-2, 13.6 × 134.3, EF-P34-1, VPIGM-4853, rectangle in (4) marks area shown in (5); (6–8) S4-4-F2-7, 6.8 × 139.3, EF-V39-3, VPIGM-4890, rectangle in (6) marks area shown in (7) and (8) at different focal levels.

Holotype

IGCAGS–WFG–676, reposited at Institute of Geology, Chinese Academy of Geological Sciences, from the lower member III of the Ediacaran Doushantuo Formation at Wangfenggang section in the Yangtze Gorges area, Hubei Province, South China (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a, fig. 8.1, 8.2).

Occurrence

Ediacaran of South China and northern India, and lower Cambrian of Siberia. South China: member II and equivalent strata of the Doushantuo Formation at Jinguadun (Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021) and Wuzhishan (Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021) in the Yangtze Gorges and surrounding areas; member III of the Doushantuo Formation at Wangfenggang and Niuping in the Yangtze Gorges area (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a). Northern India: Ediacaran Krol A Formation in the Solan area of northern India (this paper). Siberia: upper Ediacaran or lower Cambrian Oppokun Formation, Khastakhskaya borehole, Lena-Anabar Basin, north-central Siberia (Grazhdankin et al., Reference Grazhdankin, Nagovitsin, Golubkova, Karlova, Kochnev, Rogov and Marusin2020).

Description and measurements

Medium-sized to large spherical vesicles with evenly spaced processes that are short, hollow, slightly expanded at base, basally separate, distally pointed, and open to vesicle interior. Vesicle diameter difficult to measure with precision, but likely >200 μm (see Figs. 5.1, 6.1). Approximately 19–34 processes per 100 μm of vesicle periphery, process spacing 1–3 μm at base, process width 2–3 μm at base, and process length 4–11 μm. Basal expansions conical in shape and 1–2 μm in height. Apical spines of processes 2–10 μm in length and ~0.5 μm in maximum width.

Remarks

The Krol A specimens are similar to the holotype of Appendisphaera clava in vesicle size, process density, process morphology, and the size and shape of the basal expansion. The specimens are somewhat similar to A. tenuis in process length and density, but they better conform to the diagnosis of A. clava in its larger vesicle and processes with a more notable basal expansion. For comparison, the holotype of A. clava is 420 μm in vesicle diameter (vs. 87–147 μm in specimens identified as A. tenuis), and its processes have a visible basal expansion and are 12 μm in length (vs. 7–16 μm in A. tenuis) and ~1 μm in process basal width (measurements not reported for A. tenuis); as a result, process length is only 2.9% of vesicle diameter in A. clava (vs. 8–11% in A. tenuis) (Moczydłowska, Reference Moczydłowska2005; Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a).

Ouyang et al. (Reference Ouyang, Zhou, Xiao, Chen and Shao2019) illustrated two specimens of Appendisphaera clava, but one of them (their fig. 8E, F) seems to have long processes (>20 μm in length) and may belong to A. grandis.

Appendisphaera grandis Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993, emend. Moczydłowska, Reference Moczydłowska2005
Figure 7

Reference Moczydłowska, Vidal and Rudavskaya1993

Appendisphaera grandis Moczydłowska et al., p. 503, text-fig. 5, pl. 1, figs. 1, 2.

Reference Moczydłowska2005

Appendisphaera grandis; Moczydłowska, p. 294, figs. 3, 4.

non  Reference Shukla and Tiwari2014

Appendisphaera grandis; Shukla and Tiwari, p. 215, fig. 4D, E.

Reference Prasad and Asher2016

Appendisphaera grandis; Prasad and Asher, p. 42, pl. 2, figs. 3, 4.

non  Reference Sharma, Tiwari, Ahmad, Shukla, Shukla, Singh, Pandey, Ansari, Shukla and Kumar2016

Appendisphaera grandis; Sharma et al., fig. 4B.

Reference Ouyang, Guan, Zhou and Xiao2017

Appendisphaera fragilis Moczydłowska, Vidal, and Rudavskaya; Ouyang et al., fig. 8D–F.

Reference Anderson, McMahon, Macdonald, Jones and Briggs2019

Appendisphaera grandis; Anderson et al., p. 507, fig. 6A–D.

Reference Liu and Moczydłowska2019

Appendisphaera grandis; Liu and Moczydłowska, p. 48, figs. 21–23, and synonyms therein (except Appendisphaera? hemisphaerica illustrated in Hawkins et al., Reference Hawkins, Xiao, Jiang, Wang and Shi2017, fig. 9C, D; Meghystrichosphaeridium magnificum illustrated in Zhang et al., Reference Zhang, Yin, Xiao and Knoll1998, fig. 10.5, 10.6; and Liu et al., Reference Liu, Yin, Chen, Tang and Gao2013, fig. 11I, J; and Appendisphaera magnifica illustrated in Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a, figs. 19, 20; and in Hawkins et al., Reference Hawkins, Xiao, Jiang, Wang and Shi2017, fig. 9A, B).

Reference Shang, Liu and Moczydłowska2019

Appendisphaera grandis; Shang et al., p. 7, fig. 3, and synonyms therein (except Appendisphaera? hemisphaerica illustrated in fig. 9C, D of Hawkins et al., Reference Hawkins, Xiao, Jiang, Wang and Shi2017).

Reference Ouyang, Zhou, Xiao, Chen and Shao2019

Appendisphaera grandis; Ouyang et al., fig. 8I–K.

Reference Shang and Liu2020

Appendisphaera grandis; Shang and Liu, p. 156, fig. 4.

Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021

Appendisphaera grandis; Ouyang et al., fig. 10M–P.

Reference Liu, Qi, Fan, Guo, Pei, Huang, Cheng, Bian, Liu, Zhao and Zhang2021

Appendisphaera grandis; Liu et al., fig. 5.4.

Figure 7. Appendisphaera grandis. (1–4) S4-4-F2-5, 10.5 × 132.3, EF-S32-2, VPIGM-4873, rectangle in (1) marks area shown in (2), white and black arrows in (2) mark areas shown in (3) (different focal level) and (4), respectively; (5–8) DH-14-66.0-B-2, 9.8 × 120.8, EF-S21-1, VPIGM-4840, white arrow, black arrow, and rectangle in (5) mark areas shown in (6–8), respectively.

Holotype

PMU-Sib.1-R/63/2, reposited at Uppsala University, from the Ediacaran Khamaka Formation, Zapad 742 borehole at a depth of 1887.0–1894.0 m, Nepa-Botuoba region, Yakutia, Siberian (Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993, p. 503, text-fig. 5A–D).

Occurrence

Ediacaran of South China, Siberia, Australia (see Liu and Moczydłowska, Reference Liu and Moczydłowska2019, and Shang et al., Reference Shang, Liu and Moczydłowska2019, for detailed occurrence information), and India (this paper). This species also has been reported from the upper Khesen Formation at Urandush Uul in northern Mongolia (Anderson et al., Reference Anderson, Macdonald, Jones, McMahon and Briggs2017, Reference Anderson, McMahon, Macdonald, Jones and Briggs2019), which is considered terminal Ediacaran in age, although the uppermost Khesen Formation contains Cambrian-age detrital zircons (Anttila and Macdonald, Reference Anttila and Macdonald2020). The occurrence of Appendisphaera grandis in the Semri Group of the Lower Vindhyan Supergroup in the Chambal Valley of eastern Rajasthan of central-western India (Prasad and Asher, Reference Prasad and Asher2016) is intriguing because the Semri Group in central India is widely regarded as Paleo-/Mesoproterozoic in age, ca. 1600 Ma (Rasmussen et al., Reference Rasmussen, Bose, Sarkar, Banerjee, Fletcher and McNaughton2002; Ray et al., Reference Ray, Martin, Veizer and Bowring2002); this record and its age warrants further confirmation because of its profound biostratigraphic implications (Hughes, Reference Hughes2017) and because Appendisphaera grandis is the eponymous species of the early Ediacaran Appendisphaera grandis-Weissiella grandistella-Tianzhushania spinosa Assemblage Zone of Liu and Moczydłowska (Reference Liu and Moczydłowska2019).

Description and measurements

Medium-sized to large spherical vesicles with closely and evenly spaced processes that are long, hollow, cylindrical or slightly expanded at base, distally tapering, and open to vesicle interior. Vesicle diameter difficult to measure with precision due to deformation, but one specimen is ~440 μm in diameter (Fig. 7.5). Approximately 15–50 processes per 100 μm of vesicle periphery, process spacing up to 1.4 μm at base, although many processes are in basal contact with each other, process length 17–21 μm. Most processes are cylindrical (~0.5 μm in width; Fig. 7.6), although some appear to have a basal expansion supporting an apical spine (Fig. 7.3, 7.4, 7.7). We cannot exclude the possibility that the basal expansion is a diagenetic artifact; nonetheless, the apparent basal expansion measures up to 3–4 μm in width and 3–4 μm in height, and the apical spine is 12–17 μm in length and ~0.5 μm in maximum width.

Remarks

The Krol A specimens are identified as Appendisphaera grandis based on their relatively long and densely distributed processes. Some, but not all, processes in the Krol A specimens have a slightly expanded base (e.g., Fig. 7.3, 7.4), but they are otherwise similar to the holotype (Moczydłowska et al., Reference Moczydłowska, Vidal and Rudavskaya1993) and other specimens identified as Appendisphaera grandis (Liu and Moczydłowska, Reference Liu and Moczydłowska2019).

Meghystrichosphaeridium magnificum Zhang et al., Reference Zhang, Yin, Xiao and Knoll1998, is somewhat similar to Appendisphaera grandis in vesicle size, process density, and process morphology. Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a) acknowledged these similarities, but emphasized that the processes of M. magnificum are more regularly and evenly distributed, and that they taper toward a more sharply pointed distal end than those of A. grandis. Thus, they transferred this species to the genus Appendisphaera, but maintained it as a distinct species, A. magnifica. Subsequently, without providing explanation or justification, Liu and Moczydłowska (Reference Liu and Moczydłowska2019) marked M. magnificum as an invalid species and listed it as a junior synonym of A. grandis. As far as we can tell, M. magnificum is an effectively and validly published species (Zhang et al., Reference Zhang, Yin, Xiao and Knoll1998). Not knowing the basis for the synonymization proposed by Liu and Moczydłowska (Reference Liu and Moczydłowska2019), we follow Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a), Hawkins et al. (Reference Hawkins, Xiao, Jiang, Wang and Shi2017), and Ouyang et al. (Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021) and treat A. magnifica and A. grandis as distinct taxa.

Liu and Moczydłowska (Reference Liu and Moczydłowska2019) included specimens identified by Hawkins et al. (Reference Hawkins, Xiao, Jiang, Wang and Shi2017) as Appendisphaera? hemisphaerica and A. crebra (Zang in Zang and Walter, Reference Zang and Walter1992) Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014 in the synonym list of A. grandis, but no justification was provided. Similarly, Shang et al. (Reference Shang, Liu and Moczydłowska2019) included the Appendisphaera? hemisphaerica specimen illustrated by Hawkins et al. (Reference Hawkins, Xiao, Jiang, Wang and Shi2017) in the synonym list of A. grandis, again without explanation or justification. We re-examined Hawkins et al.'s (Reference Hawkins, Xiao, Jiang, Wang and Shi2017) specimens under a transmitted light microscope by adjusting the focal level, and were able to confirm that the A.? hemisphaerica specimen in Hawkins et al. (Reference Hawkins, Xiao, Jiang, Wang and Shi2017) has basally separate biform processes with a clearly defined basal expansion (~4 μm in diameter) and a thin apical spine (~1 μm in diameter), features that are compatible with A.? hemisphaerica. Although some processes of A. grandis can have a slightly widened base (Moczydłowska, Reference Moczydłowska2005), they are not biform and typically are narrower in basal width (e.g., 1–2 μm, Shang et al., Reference Shang, Liu and Moczydłowska2019; 1–3 μm, Liu and Moczydłowska, Reference Liu and Moczydłowska2019; 2–3 μm, Liu et al., Reference Liu, Qi, Fan, Guo, Pei, Huang, Cheng, Bian, Liu, Zhao and Zhang2021). Thus, the specimen illustrated in Hawkins et al. (Reference Hawkins, Xiao, Jiang, Wang and Shi2017) better fits the diagnosis of A.? hemisphaerica than that of A. grandis. The A. crebra specimen of Hawkins et al. (Reference Hawkins, Xiao, Jiang, Wang and Shi2017) is poorly preserved, and may be assigned to A. grandis given that the holotype of A. crebra may not belong to the genus Appendisphaera (Liu and Moczydłowska, Reference Liu and Moczydłowska2019).

A specimen illustrated as Appendisphaera fragilis in Ouyang et al. (Reference Ouyang, Guan, Zhou and Xiao2017) has longer and more densely arranged processes than the holotype of A. fragilis, but better fits the diagnosis of A. grandis; this specimen is also listed as a synonym of A. grandis in Liu and Moczydłowska (Reference Liu and Moczydłowska2019), Shang et al. (Reference Shang, Liu and Moczydłowska2019), and Shang and Liu (Reference Shang and Liu2020), but only the latter authors offered an explanation.

Specimens identified as Appendisphaera grandis from the Semri Group of the Lower Vindhyan Supergroup in the Chambal Valley of eastern Rajasthan of India (Prasad and Asher, Reference Prasad and Asher2016) do have thin and densely distributed processes, but their vesicles (50–80 μm in diameter) are smaller than the holotype of A. grandis (105–108 μm in diameter; Moczydłowska et al., Reference Moczydłowska, Vidal and Rudavskaya1993). As mentioned above, the occurrence of A. grandis in the Semri Group needs to be verified, considering its profound biostratigraphic implications (Hughes, Reference Hughes2017).

We agree with Liu and Moczydłowska (Reference Liu and Moczydłowska2019) that the two specimens illustrated as A. grandis in Shukla and Tiwari (Reference Shukla and Tiwari2014), one of which was also illustrated in Sharma et al. (Reference Sharma, Tiwari, Ahmad, Shukla, Shukla, Singh, Pandey, Ansari, Shukla and Kumar2016), are better assigned to A. tenuis, because their processes are proportionally shorter than those in A. grandis.

Appendisphaera? hemisphaerica Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014
Figures 8–12

Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a

Appendisphaera? hemisphaerica Liu et al., p. 17, figs. 13–15.

non  Reference Ouyang, Zhou, Guan and Wang2015

Appendisphaera? hemisphaerica; Ouyang et al., p. 215, pl. I, figs. 3, 5.

Reference Hawkins, Xiao, Jiang, Wang and Shi2017

Appendisphaera? hemisphaerica; Hawkins et al., fig. 9C, D.

Reference Shang, Moczydłowska, Liu and Liu2018

Appendisphaera? hemisphaerica; Shang et al., fig. 4B.

Reference Shang, Liu and Moczydłowska2019

Appendisphaera? hemisphaerica; Shang et al., p. 7, fig. 4A, B.

Figure 8. Appendisphaera? hemisphaerica. (1–3) DH-14-67.0-A-2, 15.8 × 111.7, EF-M11-4, VPIGM-4842, black and white arrows in (1) mark areas shown in (2, 3), respectively, at different focal levels; (4, 5) DH-14-67.0-A-2, 18.8 × 117.9, EF-J17-4, VPIGM-4843, arrow in (4) marks area shown in (5) at a different focal level; (6–8) S4-4-F2-7, 17.0 × 125.9, EF-L26-3, VPIGM-4887, rectangle in (6) marks area shown in (7), arrow in (7) marks area shown in (8) with a 180° rotation; (9, 10) DH-14-66.0-B-2, 11.4 × 107.4, EF-Q7-4, VPIGM-4839, arrow in (9) marks area shown in (10) at a different focal level.

Holotype

IGCAGS–WFG–248, reposited at Institute of Geology, Chinese Academy of Geological Sciences, from the lower member III of the Ediacaran Doushantuo Formation at Wangfenggang section in the Yangtze Gorges area, Hubei Province, South China (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a, fig. 13.1–13.3).

Occurrence

Ediacaran of South China and northern India. South China: member II of the Doushantuo Formation at Siduping section in the Zhangjiajie area, Hunan Province (Hawkins et al., Reference Hawkins, Xiao, Jiang, Wang and Shi2017); member III of the Doushantuo Formation at Wangfenggang and Niuping sections in the Yangtze Gorges area of Hubei Province (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a); Doushantuo Formation at Liujing section in Guizhou Province (Shang et al., Reference Shang, Liu and Moczydłowska2019). Northern India: Krol A Formation at Solan of northern India (this paper).

Description and measurements

Medium-sized to large spherical vesicles with closely and evenly spaced biform processes that are characterized by an easily recognizable basal expansion subtending a thin and long apical spine. Processes open to vesicle interior. Vesicle diameter ~300 μm, as estimated from three specimens (Figs. 8.1, 8.9, 9.3). Approximately 13–21 processes per 100 μm of vesicle periphery, process spacing 1–3 μm at base, but many processes are in basal contact, and process length 12–29 μm. Basal expansion conical and often inflated (Fig. 9.2, 9.5, 9.7), 3–6 μm in width, and 2–4 μm in height. Apical spine thin and cylindrical in shape, ~1 μm in width, and 7–25 μm in length.

Figure 9. Appendisphaera? hemisphaerica. (1, 2) DH-14-67.0-A-2, 24.0 × 117.8, EF-D17-2, VPIGM-4844, arrow in (1) marks area shown in (2) at a different focal level; (3–5) S4-4-F2-5-2, 2.2 × 130.5, EF-AA31-1, VPIGM-4883, rectangle and arrow in (3) mark areas shown in (4, 5), respectively, at different focal levels; (6, 7) S4-4-F2-5-2, 5.6×129.0, EF-W29-4, VPIGM-4884, arrow in (6) marks area shown in (7) at a different focal level; (8–10) S4-4-F1-3, 16.3 × 125.9, EF-M26-1, VPIGM-4870, rectangle in (8) marks area shown in (9, 10) at different focal levels.

Remarks

Appendisphaera? hemisphaerica has a combination of features that are characteristic of Appendisphaera (thin and densely distributed processes) and Mengeosphaera (biform processes with a prominent basal expansion). For this reason, this species was tentatively placed in the genus Appendisphaera (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a). Appendisphaera? hemisphaerica is similar to several Mengeosphaera species in biform processes with a relatively long apical spine, such as M. gracilis Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014, M. latibasis Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014, and M. uniformis Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014. The main differentiator is the size and shape of the basal expansion. For reference, the basal expansion is 7–8 μm, 10–15 μm, and ~5 μm wide, respectively, for the holotypes of the three Mengeosphaera species listed above. Both M. latibasis and M. uniformis have an obtusely domical basal expansion, whereas M. gracilis has a conical basal expansion. However, specimens illustrated as Mengeosphaera gracilis in Liu and Moczydłowska (Reference Liu and Moczydłowska2019) have measurements of process size, shape, and density overlapping those of the holotype of A.? hemisphaerica. It is possible that A.? hemisphaerica and Mengeosphaera gracilis are synonymous, in which case the former species would take priority. At present, we follow Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a) and treat A.? hemisphaerica and Mengeosphaera gracilis as two distinct species, with the processes of the latter species bearing a relatively larger basal expansion and a relatively shorter apical spine.

A specimen illustrated as Appendisphaera? hemisphaerica in Ouyang et al. (Reference Ouyang, Zhou, Guan and Wang2015) was subsequently identified by Ouyang et al. (Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021) as Appendisphaera heliaca (Liu and Moczydłowska, Reference Liu and Moczydłowska2019) Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021, because the basal expansions of the processes in this specimen are thought to be a taphonomic artifact related to degradation. As discussed under Appendisphaera grandis, the specimen illustrated as A.? hemisphaerica in Hawkins et al. (Reference Hawkins, Xiao, Jiang, Wang and Shi2017) has basally separate biform processes with a clearly defined basal expansion. Thus, this specimen belongs to A.? hemisphaerica rather than A. grandis.

Appendisphaera longispina Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014
Figures 13, 14

Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a

Appendisphaera longispina Liu et al., p. 21, figs. 17, 18, and synonyms therein.

Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a

Appendisphaera crebra (Zang in Zang and Walter, Reference Zang and Walter1992); Liu et al., p. 17, figs. 10, 11.

Reference Liu and Moczydłowska2019

Appendisphaera longispina; Liu and Moczydłowska, p. 54, fig. 25.

Reference Shang, Liu and Moczydłowska2019

Appendisphaera longispina; Shang et al., p. 8, fig. 4C, D.

Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021

Appendisphaera longispina; Ouyang et al., fig. 11G, H.

Figure 13. Appendisphaera longispina. (1–3) DH-14-67.0-C, 8.7 × 127.2, EF-T27, VPIGM-4850, rectangle and arrow in (1) mark areas shown in (2, 3), respectively, at different focal levels; (4–6) DH-14-67.0-C, 14.0 × 133.3, EF-N33-4, VPIGM-4849, white and black arrows in (4) mark areas shown in (5, 6), respectively, at different focal levels; (7, 8) DH-14-67.0-C-2, 18.7 × 133.2, EF-K33-1, VPIGM-4857, arrow in (7) marks area shown in (8).

Figure 14. Appendisphaera longispina. (1, 2) DH-14-68.0-B, 11.5 × 140.1, EF-Q40-1, VPIGM-4864, arrow in (1) marks area shown in (2); (3–5) S4-4-F2-8-A, 17.3 × 109.6, EF-K9-4, VPIGM-4906, rectangle in (3) marks area shown in (4, 5) at two different focal levels; (6–8) S4-4-F2-15, 14.2 × 140.4, EF-O40, VPIGM-4900, rectangle and arrow in (6) mark areas shown in (7, 8), respectively, at different focal levels.

Holotype

IGCAGS–NPIII–141, reposited at Institute of Geology, Chinese Academy of Geological Sciences, from the upper member III of the Ediacaran Doushantuo Formation at Niuping section in the Yangtze Gorges area, Hubei Province, South China (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a, fig. 18.3, 18.4).

Occurrence

Ediacaran of South China and northern India. South China: member II of the Doushantuo Formation at Jiuqunao and Xiaofenghe sections (Liu and Moczydłowska, Reference Liu and Moczydłowska2019) and at Wuzhishan section (Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021), Yangtze Gorges area, Hubei Province; member III of the Doushantuo Formation at Niuping section in the Yangtze Gorges area, Hubei Province (described as A. crebra and A. longispina in Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a); Doushantuo Formation at Liujing section in Guizhou Province (Shang et al., Reference Shang, Liu and Moczydłowska2019). Northern India: Krol A Formation in the Solan area (this paper).

Description and measurements

Large spherical vesicles with long, homomorphic, and evenly spaced processes that have a conical basal expansion gradually transitioning into a thin apical spine. Processes open to vesicle interior. Vesicle diameter ~250–300 μm, as estimated from two specimens (Fig. 13.1, 13.4). Processes 21–32 μm in length (~10% of vesicle diameter), densely distributed, ~16–24 processes per 100 μm of vesicle periphery, mostly in contact at base, but can be spaced at 1–2 μm. Basal expansion conical or slightly deflated (Fig. 13.2), 3–5 μm in width, and 2–5 μm in height. Apical spine thin and cylindrical, ~1 μm in width, and 19–30 μm in length.

Remarks

Appendisphaera longispina is somewhat similar to A. grandis and A.? hemisphaerica. However, the basal expansion in A. longispina is more prominent than in A. grandis. Relative to A.? hemisphaerica, A. longispina has longer processes, a taller or longer basal expansion, and a more gradual transition from the basal expansion to the apical spine. The current specimens better fit the diagnosis of A. longispina than A.? hemisphaerica.

Following Liu and Moczydłowska (Reference Liu and Moczydłowska2019), specimens illustrated by Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a) as Appendisphaera crebra (Zang in Zang and Walter, Reference Zang and Walter1992) Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014 are transferred to Appendisphaera longispina.

Appendisphaera setosa Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014
Figures 15, 16

Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a

Appendisphaera setosa Liu et al., p.31, figs. 21, 22, and synonyms therein.

Reference Liu and Moczydłowska2019

Appendisphaera setosa; Liu and Moczydłowska, p. 56, fig. 27.

Reference Shang, Liu and Moczydłowska2019

Appendisphaera setosa; Shang et al., p. 10, fig. 4E–J.

?Reference Grazhdankin, Nagovitsin, Golubkova, Karlova, Kochnev, Rogov and Marusin2020

Appendisphaera setosa; Grazhdankin et al., fig. 3A.

Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021

Appendisphaera setosa; Ouyang et al., fig. 11K, O.

Figure 15. Appendisphaera setosa. (1–6) S4-4-F2-5, 19.4 × 131.9, EF-J32-1, VPIGM-4875, rectangle in (1) marks area shown in (2, 3) at different focal levels, white arrow in (3) marks area shown in (4), and white and black arrows in (1) mark areas shown in (5, 6), respectively; (7–9) DH-14-66.0-C-2, 11.9 × 117.3, EF-Q17-2, VPIGM-4841, arrow and rectangle in (7) mark areas shown in (8, 9), respectively, at a different focal level.

Figure 16. Appendisphaera setosa. (1, 2) DH-14-65.0-D, 11.6 × 140.6, EF-Q40-2, VPIGM-4837, rectangle in (1) marks area shown in (2); (3–8) S4-4-F2-18A, 21.5 × 133.2, EF-E33-3, VPIGM-4910, rectangle and white arrow in (3) mark areas shown in (4, 5), respectively; (6–8) show the same area indicated by the black arrow in (3) at different focal levels.

Holotype

IGCAGS–NPIII–592, reposited at Institute of Geology, Chinese Academy of Geological Sciences, from the upper member III of the Ediacaran Doushantuo Formation at Niuping section in the Yangtze Gorges area, Hubei Province, South China (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a, fig. 22.8, 22.9).

Occurrence

Ediacaran of South China and northern India, and possibly early Cambrian of northern Siberia. South China: member II of the Doushantuo Formation at Jinguadun and Wuzhishan sections, Yangtze Gorges area, Hubei Province (Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021); member III of the Doushantuo Formation at Niuping and Wangfenggang sections (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a) as well as Baiguoyuan, Dishuiyan, and Chenjiayuanzi sections (Liu and Moczydłowska, Reference Liu and Moczydłowska2019), Yangtze Gorges area, Hubei Province; Doushantuo Formation at Liujing section in Guizhou Province (Shang et al., Reference Shang, Liu and Moczydłowska2019). Northern India: Ediacaran Krol A Formation in the Solan area (this paper). Possible occurrence in Siberia: upper Ediacaran or lower Cambrian Oppokun Formation, Khastakhskaya borehole, Lena-Anabar Basin, north-central Siberia (Grazhdankin et al., Reference Grazhdankin, Nagovitsin, Golubkova, Karlova, Kochnev, Rogov and Marusin2020).

Description and measurements

Specimens assigned to this species are characterized by large vesicles and thin, cylindrical, hollow, homomorphic, evenly distributed, basally separate, and relatively straight processes that lack a basal expansion. Processes open to vesicle interior (Fig. 15.4), but the communication between hollow process and vesicle interior is often obscured by the accumulation of organic matter within the extremely thin processes. Vesicle diameter ~250 μm, as estimated from one completely preserved specimen (Fig. 15.1). Processes 19–29 μm in length (~11% of vesicle diameter, estimated from specimen in Fig. 15.1) and ~1.5 μm in diameter, ~9–12 processes per 100 μm of vesicle periphery, and process spacing 7–18 μm.

Remarks

Appendisphaera setosa is somewhat similar to A. tenuis and A. fragilis. However, A. tenuis has relatively shorter and slightly conical processes. The holotype of A. fragilis is poorly preserved, with a small number of cylindrical processes covering a small area of the vesicle (Moczydłowska et al., Reference Moczydłowska, Vidal and Rudavskaya1993, text-fig. 6A, B). Although its process length (11–20 μm; Moczydłowska et al., Reference Moczydłowska, Vidal and Rudavskaya1993) is comparable to that of the holotype of A. setosa (16 μm; Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a), the proportional process length is much greater in A. fragilis (16–19% of vesicle diameter; Moczydłowska, Reference Moczydłowska2005) than in A. setosa (estimated ~10% of vesicle diameter; Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a). On the other hand, specimens illustrated as A. fragilis in Shang et al. (Reference Shang, Liu and Moczydłowska2019) have much smaller proportional process length (e.g., 7–11% of vesicle diameter) relative to the holotype. Considering their relatively large vesicles and relatively straight processes, which are characteristic of A. setosa, the Krol A specimens are better placed in A. setosa than in A. fragilis.

A specimen illustrated as Appendisphaera setosa (Grazhdankin et al., Reference Grazhdankin, Nagovitsin, Golubkova, Karlova, Kochnev, Rogov and Marusin2020, fig. 3A) is similar to the holotype in vesicle size, process width, and absolute and proportional process length. However, some of its processes have a slightly expanded base. Thus, we regard its identification as A. setosa provisional. A possible alternative would be A. tenuis.

Appendisphaera tenuis Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993, emend. Moczydłowska, Reference Moczydłowska2005
Figure 17

Reference Moczydłowska, Vidal and Rudavskaya1993

Appendisphaera tenuis Moczydłowska et al., p. 506, text-fig. 7.

Reference Moczydłowska2005

Appendisphaera tenuis; emend. Moczydłowska, p. 296, fig. 5.

Reference Shukla and Tiwari2014

Appendisphaera grandis; Shukla and Tiwari, p. 215, fig. 4D, E.

Reference Sharma, Tiwari, Ahmad, Shukla, Shukla, Singh, Pandey, Ansari, Shukla and Kumar2016

Appendisphaera grandis; Sharma et al., fig. 4B.

Reference Prasad and Asher2016

Appendisphaera tenuis; Prasad and Asher, p. 44, pl. 3, figs. 3–6.

Reference Liu and Moczydłowska2019

Appendisphaera tenuis; Liu and Moczydłowska, p. 61, figs. 29, 30, and synonyms therein.

Reference Anderson, McMahon, Macdonald, Jones and Briggs2019

Appendisphaera tenuis; Anderson et al., p. 509, fig. 6H, I.

Reference Shang, Liu and Moczydłowska2019

Appendisphaera tenuis; Shang et al., p. 10, fig. 5.

Reference Shang and Liu2020

Appendisphaera tenuis; Shang and Liu, p. 157, fig. 5A, B.

Reference Vorob'Eva and Petrov2020

Appendisphaera tenuis; Vorob'Eva and Petrov, p. 370, pl. I, figs. 3, 4.

Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021

Appendisphaera tenuis; Ouyang et al., fig. 11Q, R.

Figure 17. Appendisphaera tenuis. (1, 2) S4-4-F2-6-A, 9.3 × 110.7, EF-T10-2, VPIGM-4904, arrow in 1 marks area shown in (2); (3, 4) S4-4-F2-12-A, 12.0 × 142.8, EF-Q42-2, VPIGM-4907, arrow in (3) marks area shown in (4); (5–8) DH-14-67.0-C-2, 11.1 × 139.3, EF-Q39-4, VPIGM-4858, white and black rectangles in (5) mark areas magnified in (6, 7), respectively, and (8) illustrates the same area as (7) at a different focal level, showing the hollow nature of processes, as seen in transverse cross section.

Holotype

PMU-Sib.1-M/33, reposited at Uppsala University, from the Ediacaran Khamaka Formation, Zapad 742 borehole at a depth of 1887.0–1894.0 m, Nepa-Botuoba region, Yakutia, Siberian (Moczydłowska et al., Reference Moczydłowska, Vidal and Rudavskaya1993, p. 506, text-fig. 7).

Occurrence

Ediacaran of South China, Siberia, Australia, and India (see Liu and Moczydłowska, Reference Liu and Moczydłowska2019; Shang et al., Reference Shang, Liu and Moczydłowska2019, for detailed occurrence information). Appendisphaera tenuis has been reported from the upper Khesen Formation at Urandush Uul in northern Mongolia (Anderson et al., Reference Anderson, Macdonald, Jones, McMahon and Briggs2017, Reference Anderson, McMahon, Macdonald, Jones and Briggs2019), which is regarded as terminal Ediacaran, although the uppermost Khesen Formation contains Cambrian-age detrital zircons (Anttila and Macdonald, Reference Anttila and Macdonald2020). It has also been reported from the Semri Group of the Lower Vindhyan Supergroup in the Chambal Valley of eastern Rajasthan of central-western India (Prasad and Asher, Reference Prasad and Asher2016). As discussed under Appendisphaera grandis, the Semri Group in central India is widely regarded as Paleo-/Mesoproterozoic in age (Rasmussen et al., Reference Rasmussen, Bose, Sarkar, Banerjee, Fletcher and McNaughton2002; Ray et al., Reference Ray, Martin, Veizer and Bowring2002), and it is important to verify the occurrence of Appendisphaera grandis and A. tenuis in this unit.

Description and measurements

Large vesicles with short, thin, hollow, slightly conical, evenly spaced, and basally separate processes. Vesicle ~265–364 μm in diameter (Fig. 17.1, 17.5; the specimen illustrated in Fig. 17.3 is poorly preserved, but has a medium-sized vesicle). Approximately 22–33 processes per 100 μm of vesicle periphery, process length 7–12 μm (or 2–3% of vesicle diameter), process spacing 2–4 μm at base, and process width 0.7–0.9 μm. Some processes in the specimen illustrated in Fig. 17.5–17.8 appear to have an expanded base (~2 μm wide and ~1.3 μm high), but this is an inconsistent feature (e.g., Fig. 17.6, 17.7) and seems an artifact resulting from degradation of the vesicle wall. Thus, we choose to place this specimen in Appendisphaera tenuis rather than A. clava.

Remarks

The Krol A specimens are identified as Appendisphaera tenuis based on their short, thin, hollow, and slightly conical processes, although they are larger in vesicle size than the holotype. Appendisphaera tenuis is similar to A. clava and Cymatiosphaeroides forabilatus in having relatively short processes. However, the processes of A. clava are more densely arranged and have a well-defined, albeit small basal expansion, and C. forabilatus has presumably solid processes that penetrate an outer membrane. Admittedly, when poorly preserved, these features can be difficult to discern. For example, strong degradation and displacement of organic matter by mineral recrystallization at the junction between cell wall and basal processes may give a false impression of a basal expansion, and hollow processes may appear solid due to accumulation of organic matter within the processes. In such cases, we depend on consistent process morphology and coherent preservation of organic walls to make a taxonomic decision, but even so, there are specimens that cannot be confidently assigned to one versus another species.

As discussed under Appendisphaera grandis, the two specimens illustrated as A. grandis in Shukla and Tiwari (Reference Shukla and Tiwari2014) and in Sharma et al. (Reference Sharma, Tiwari, Ahmad, Shukla, Shukla, Singh, Pandey, Ansari, Shukla and Kumar2016) have been re-assigned to A. tenuis because of their short processes (Liu and Moczydłowska, Reference Liu and Moczydłowska2019). Also, as discussed under Appendisphaera setosa, a Cambrian acanthomorph identified as A. setosa (Grazhdankin et al., Reference Grazhdankin, Nagovitsin, Golubkova, Karlova, Kochnev, Rogov and Marusin2020, fig. 3A) may belong to A. tenuis, although a closer examination is needed to confirm or reject this suspicion.

Finally, specimens identified as A. tenuis from the Semri Group of the Lower Vindhyan Supergroup in the Chambal Valley of eastern Rajasthan of India (Prasad and Asher, Reference Prasad and Asher2016) have important biostratigraphic implications if the hosting rocks turn out to be Mesoproterozoic (Hughes, Reference Hughes2017). The Semri specimens have relatively smaller vesicles (50–80 μm in diameter) than the holotype of A. tenuis (115–148 μm in diameter; Moczydłowska et al., Reference Moczydłowska, Vidal and Rudavskaya1993), and as such, their relative process length (as a percentage of vesicle diameter) is greater, but they are otherwise similar to the holotype in process density and absolute process length. Perhaps both A. grandis and A. tenuis have extremely long stratigraphic ranges, from the Paleo–Mesoproterozoic (Prasad and Asher, Reference Prasad and Asher2016) to the terminal Ediacaran–Cambrian (Anderson et al., Reference Anderson, McMahon, Macdonald, Jones and Briggs2019; Grazhdankin et al., Reference Grazhdankin, Nagovitsin, Golubkova, Karlova, Kochnev, Rogov and Marusin2020).

Type species

Asterocapsoides sinensis Yin and Li, Reference Yin and Li1978, emend. Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014.

Other species

Asterocapsoides fluctuensis Liu and Moczydłowska, Reference Liu and Moczydłowska2019; A. robustus Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014; A. wenganensis (Chen and Liu, Reference Chen and Liu1986) Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014.

Remarks

In addition to the named species, several unnamed specimens of Asterocapsoides have been reported from Ediacaran deposits, including (1) Asterocapsoides sp. from the Infra-Krol Formation in the Solan area of the Lesser Himalaya, northern India (Tiwari and Knoll, Reference Tiwari and Knoll1994; Tiwari and Pant, Reference Tiwari and Pant2004), which may be A. wenganensis; (2) Asterocapsoides sp. A and sp. B from the Krol A Formation in the Khanog and Rajgarh synclines of the Lesser Himalaya, northern India (Shukla and Tiwari, Reference Shukla and Tiwari2014), which have acutely conical processes (<10 μm in length) that are much shorter than those of existing species of Asterocapsoides; (3) Asterocapsoides sp. from the Doushantuo Formation at Baizhu of Hubei Province, South China (Yang et al., Reference Yang, Pang, Chen, Zhong and Yang2020), which resembles A. wenganensis, but has occasionally branching processes; (4) two specimens of Asterocapsoides sp. from the Doushantuo Formation at Chaoyang of Jiangxi Province, South China (Zhou et al., Reference Zhou, Chen and Xue2002), one of which has been assigned to A. sinensis by Xiao et al. (Reference Xiao, Zhou, Liu, Wang and Yuan2014); and (5) two specimens of Asterocapsoides sp. from the Vychegda Formation at Keltma, Timan Ridge, East European Platform, Russia (Vorob'Eva et al., Reference Vorob'Eva, Sergeev and Knoll2009), one of which may be A. sinensis (see Remarks under A. sinensis).

Asterocapsoides sinensis Yin and Li, Reference Yin and Li1978, emend. Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014
Figure 18

Reference Yin and Li1978

Asterocapsoides sinensis Yin and Li, p. 87, pl. 9, fig. 7.

?Reference Knoll1992

Asterocapsoides sinensis; Knoll, p. 762, pl. 6, figs. 5, 6.

Reference Zhang, Yin, Xiao and Knoll1998

Asterocapsoides sinensis; Zhang et al., p. 24, fig. 5.10 (neotype).

Reference Yuan, Xiao, Yin, Knoll, Zhou and Mu2002

Asterocapsoides sinensis; Yuan et al., p. 70, fig. 87.

Reference Zhou, Chen and Xue2002

Asterocapsoides sp.; Zhou et al., pl. 2, fig. 6 (part).

?Reference Tiwari and Pant2004

Asterocapsoides sinensis; Tiwari and Pant, p. 10, fig. 5C–F.

Reference Yin, Liu, Gao, Wang, Tang and Liu2007

Asterocapsoides sinensis; Yin et al., pl. 13, fig. 1.

Reference Liu, Yin, Gao, Tang and Chen2009

Asterocapsoides sinensis; Liu et al., fig. 2g.

Reference Vorob'Eva, Sergeev and Knoll2009

Asterocapsoides sp.; Vorob'Eva et al., p. 175, fig. 7.10 (part).

?Reference Sharma, Kumar, Tiwari, Shukla, Pandey, Srivastava and Banerjee2012

Asterocapsoides sinensis; Sharma et al., fig. 4k, l.

Reference Xiao, Zhou, Liu, Wang and Yuan2014

Asterocapsoides sinensis; Xiao et al., p. 11, fig. 5.1–5.3, and synonyms therein.

Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a

Asterocapsoides sinensis; Liu et al., p. 31, fig. 24.1, 24.2.

Reference Hawkins, Xiao, Jiang, Wang and Shi2017

Asterocapsoides sinensis; Hawkins et al., fig. 8F.

?Reference Sharma, Shukla and Sergeev2021

Asterocapsoides sinensis; Sharma et al., fig. 9B, C.

Figure 18. Asterocapsoides sinensis. (1, 2) DH-14-65.0-B, 14.3 × 134.6, EF-N34-4, VPIGM-4833, arrow in (1) marks area shown in (2) at a different focal level; (3, 4) DH-14-65.0-B, 15.8 × 132.0, EF-M31-2, VPIGM-4834, arrow in (3) marks area shown in (4).

Neotype

The holotype designated by Yin and Li (Reference Yin and Li1978) was damaged and a neotype was subsequently designated by Zhang et al. (Reference Zhang, Yin, Xiao and Knoll1998). The neotype is reposited in the Nanjing Institute of Geology and Palaeontology (thin section R-19-3; Zhang et al., Reference Zhang, Yin, Xiao and Knoll1998, fig. 5.10).

Occurrence

Ediacaran of South China, northern India, and Russia. South China: Doushantuo Formation at Tianzhushan, Changyang, Hubei Province (Yin and Li, Reference Yin and Li1978; Zhang et al., Reference Zhang, Yin, Xiao and Knoll1998); upper Doushantuo Formation at Chaoyang, Shangrao, Jiangxi Province (Zhou et al., Reference Zhou, Chen and Xue2002); Doushantuo Formation at Wangfenggang, Yangtze Gorges area, Hubei Province (Yin et al., Reference Yin, Liu, Gao, Wang, Tang and Liu2007); member III of Doushantuo Formation at Wangfenggang and Niuping, Yangtze Gorges area, Hubei Province (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a); member II of Doushantuo Formation at Siduping, Hunan Province (Hawkins et al., Reference Hawkins, Xiao, Jiang, Wang and Shi2017); lower Doushantuo Formation (equivalent to unit 4 at Weng'an or upper member II in the Yangtze Gorges area) at Wanjiagou section, Zhangcunping, Hubei Province (Liu et al., Reference Liu, Yin, Gao, Tang and Chen2009); Doushantuo Formation at Weng'an, Guizhou Province (Yuan et al., Reference Yuan, Xiao, Yin, Knoll, Zhou and Mu2002; Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014). Northern India: Krol A Formation, Solan area (this paper).

Veis et al. (Reference Veis, Vorob'Eva and Golubkova2006) and Vorob'Eva et al. (Reference Vorob'Eva, Sergeev and Semikhatov2006) mentioned the occurrence of Asterocapsoides sinensis in the Ediacaran Vychegda Formation in the Timan Ridge, East European Platform, Russia, but did not provide illustrations. Subsequently, Vorob'Eva et al. (Reference Vorob'Eva, Sergeev and Knoll2009) illustrated two specimens as Asterocapsoides sp., one of which, in our opinion, can be assigned to A. sinensis (see Remarks below). However, A. sinensis specimens from the Scotia Group of Svalbard (Knoll, Reference Knoll1992) and the Infra-Krol and Krol A formations in northern India (Tiwari and Pant, Reference Tiwari and Pant2004; Sharma et al., Reference Sharma, Kumar, Tiwari, Shukla, Pandey, Srivastava and Banerjee2012, Reference Sharma, Shukla and Sergeev2021, fig. 9B) have acutely conical processes and their identification as A. sinensis remains uncertain (see Remarks below).

Description and measurements

Large spheroidal vesicles with sparsely distributed processes open to vesicle interior. Processes conical, often obtuse, and basally separate from each other. An inner wall is present within the vesicle, and remnants of an outer membrane also may be present. Vesicle diameter 300–400 μm, only a few (<10) processes per circumferential view, process spacing 12 μm or more at base, process width ~30 μm at base, process length 20–40 μm (5–14% of vesicle diameter).

Remarks

One could conceivably argue that the sparse processes in the specimens illustrated in Figure 18 may be deformation artifacts. Indeed, both specimens in our collection are deformed, particularly the inner wall. However, the processes on the vesicle wall do not coincide spatially with the deformation in the inner wall, leading us to favor the interpretation that the processes are biological structures rather than deformational folds of the vesicle wall. If our interpretation is correct, then the Krol A specimens best fit Asterocapsoides sinensis on the basis of their large vesicle size, the presence of an inner wall, as well as sparse, widely separate, and mostly obtusely conical processes.

Two specimens of Asterocapsoides sp. (Zhou et al., Reference Zhou, Chen and Xue2002, pl. 2, fig. 6; Vorob'Eva et al., Reference Vorob'Eva, Sergeev and Knoll2009, fig. 7.10) from the Doushantuo Formation in South China and the Vychegda Formation in Russia also display these features, and thus can be regarded as A. sinensis. On the other hand, specimens of A. sinensis from the Infra-Krol Formation (Tiwari and Pant, Reference Tiwari and Pant2004; Sharma et al., Reference Sharma, Kumar, Tiwari, Shukla, Pandey, Srivastava and Banerjee2012) and Krol A Formation in northern India (Sharma et al., Reference Sharma, Shukla and Sergeev2021, fig. 9B) have basally separate and acutely conical processes, as do specimens of Asterocapsoides sp. from the same formation (Tiwari and Knoll, Reference Tiwari and Knoll1994; Tiwari and Pant, Reference Tiwari and Pant2004); these may be either A. robustus or A. wenganensis. One of the Krol A specimens illustrated as A. sinensis in Sharma et al. (Reference Sharma, Shukla and Sergeev2021, fig. 9C) is poorly preserved and does not exhibit diagnostic features of this species. Finally, the specimen illustrated as A. sinensis from the Scotia Group of Svalbard (Knoll, Reference Knoll1992) has sparsely distributed, basally separate, and acutely conical processes that seem to be divided internally by transverse septa; this specimen is akin to A. wenganensis or Weissiella grandistella Vorob'Eva et al., Reference Vorob'Eva, Sergeev and Knoll2009, depending on future verification of the presence of transverse septa within processes.

Type species

Cavaspina acuminata (Kolosova, Reference Kolosova1991) Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993.

Other species

Cavaspina basiconica Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993; C. conica Liu and Moczydłowska, Reference Liu and Moczydłowska2019; C. uria (Nagovitsin and Faizullin in Nagovitsin et al., Reference Nagovitsin, Faizullin and Yakshin2004) Nagovitsin and Moczydłowska in Moczydłowska and Nagovitsin, Reference Moczydłowska and Nagovitsin2012.

Remarks

Liu and Moczydłowska (Reference Liu and Moczydłowska2019) regarded Cavaspina amplitudinis Willman in Willman and Moczydłowska, Reference Willman and Moczydłowska2011, as a junior synonym of Appendisphaera tenuis Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993.

Cavaspina tiwariae Xiao new species
Figure 19

Reference Shukla and Tiwari2014

Unnamed Form A, Shukla and Tiwari, p. 219, fig. 6C, D.

Figure 19. Cavaspina tiwariae Xiao new species. (1–4) Holotype, DH-14-65.0-A, 14.5 × 130.0, EF-N30-1, VPIGM-4830, (2–4) show the same area indicated by the arrow in (1) at different focal levels.

Holotype

VPIGM-4830, thin section DH-14-65.0-A, Olympus BX-51 coordinates 14.5 × 130.0, England Finder coordinates N30-1, illustrated in Figure 19, reposited in Museum of Geosciences at Virginia Tech, from Krol A Formation in Solan area, Lesser Himalaya, northern India.

Diagnosis

A species of Cavaspina with a medium-sized vesicle bearing sparse, deflated, and obtusely conical processes.

Occurrence

Thus far only known from the Ediacaran Krol A Formation in the Solan area, Lesser Himalaya, northern India (Shukla and Tiwari, Reference Shukla and Tiwari2014; this paper).

Description and measurements

Medium-sized spherical vesicles with sparsely distributed and widely separate processes that are short, deflated, obtusely conical, and open to vesicle interior. The transition from processes to vesicle wall is gradual. Vesicle diameter ~150 μm, fewer than 20 processes per circumferential view, process spacing 19–28 μm at apex (spacing at base is difficult to measure because the transition from processes to vesicle wall is gradual), process width up to 8 μm at base, process length up to 5 μm (~3% of vesicle diameter).

Etymology

In honor of Dr. Meera Tiwari, who pioneered the study of microfossils from the Infra-Krol and Krol A formations in the Lesser Himalaya and published a specimen that is here regarded as conspecific to this new species (Shukla and Tiwari, Reference Shukla and Tiwari2014, fig. 6C, D).

Remarks

The specimen illustrated here is somewhat similar to Asterocapsoides sinensis (Fig. 18) in its sparsely distributed, relatively short, and obtusely conical processes. However, it can be distinguished by its deflated processes, much smaller vesicle size, and the lack of an inner wall and an outer wall, which are thought to be diagnostic of A. sinensis (Liu and Moczydłowska, Reference Liu and Moczydłowska2019), although Xiao et al. (Reference Xiao, Zhou, Liu, Wang and Yuan2014) pointed out that these additional walls (particularly the inner wall) could be lost during diagenesis. This specimen is also similar to Polygonium sp. of Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a) in its sparsely distributed processes that gradually transition at base to vesicle wall, but its processes are much smaller than those of the latter species. It better fits the genus Cavaspina, which is characterized by relatively short and sparsely distributed processes that are generally conical in shape (Moczydłowska et al., Reference Moczydłowska, Vidal and Rudavskaya1993). In particular, it is similar to the type species of Cavaspina, C. acuminata, in its sparsely distributed, relatively short, and conical processes. However, the Krol A specimen can be differentiated by its larger vesicle as well as its deflated and obtusely conical processes, which are distinct from the acutely conical processes (1 μm wide and 3–5 μm long) of C. acuminata. The Krol A specimen is also somewhat similar to Cavaspina uria in process size, but the latter species has a smaller vesicle size (80–130 μm), acutely conical processes (5–11 μm long and 4–12 μm wide at base), and more closely spaced processes (>15 processes in circumferential view; estimated from Moczydłowska and Nagovitsin, Reference Moczydłowska and Nagovitsin2012, fig. 4G, I). More importantly, the processes of C. uria are not deflated. Thus, a new species is erected here on the basis the specimen illustrated in Figure 19 and a morphologically similar specimen previously published from the same stratigraphic unit in the same area (Shukla and Tiwari, Reference Shukla and Tiwari2014).

Type species

Cymatiosphaeroides kullingii Knoll, Reference Knoll1984, emend. Shang et al., Reference Shang, Liu and Moczydłowska2019

Other species

Cymatiosphaeroides forabilatus Liu and Moczydłowska, Reference Liu and Moczydłowska2019; C. yinii Yuan and Hofmann, Reference Yuan and Hofmann1998.

Remarks

Cymatiosphaeroides dilutopilum Zang in Zang and Walter (Reference Zang and Walter1992) and C. pilatopilum Zang in Zang and Walter (Reference Zang and Walter1992) were synonymized and transferred to Appendisphaera dilutopila (Zang in Zang and Walter, Reference Zang and Walter1992) Grey, Reference Grey2005, although some non-holotype specimens illustrated in Zang and Walter (Reference Zang and Walter1992) as C. dilutopilum and C. pilatopilum have been reassigned by Grey (Reference Grey2005) to Appendisphaera barbata and Knollisphaeridium triangulum (Zang in Zang and Walter, Reference Zang and Walter1992) Willman and Moczydłowska, Reference Willman and Moczydłowska2008, respectively. More recently, Liu and Moczydłowska (Reference Liu and Moczydłowska2019, p. 61) considered Appendisphaera dilutopila as a synonym of Appendisphaera tabifica.

The genus Cymatiosphaeroides was originally diagnosed as a double-walled acanthomorph with thin and solid processes arising from the inner wall and supporting the outer wall (Knoll, Reference Knoll1984). It was later emended to emphasize that the outer wall can be a single-layered or multilamellate structure (Knoll et al., Reference Knoll, Swett and Mark1991). The diagnosis was recently emended again by Shang et al. (Reference Shang, Liu and Moczydłowska2019), who diagnosed the genus Cymatiosphaeroides as a double-walled acanthomorph with thin, hollow, and cylindrical processes. It remains to be verified whether the holotype of the type species, C. kullingii, has hollow processes; this feature cannot be determined with confidence from the published illustrations (Knoll, Reference Knoll1984, fig. 9A, B) because the processes are extremely thin (~1 μm in width). Nonetheless, we follow the emendation of Shang et al. (Reference Shang, Liu and Moczydłowska2019) so that C. forabilatus, which has hollow processes (see below), can be included in the genus Cymatiosphaeroides.

The genus Cymatiosphaeroides and its type species, C. kullingii, have extremely long stratigraphic distributions. The oldest known occurrences of C. kullingii are from the ~1.6 Ga Chitrakoot Formation in the Vindhyan Basin, central India (Anbarasu, Reference Anbarasu2001; Singh and Sharma, Reference Singh and Sharma2014). Specimens identified as Shuiyousphaeridium echinulatum Yin and Gao, Reference Yin and Gao1999, from the Chitrakoot Formation (Singh and Sharma, Reference Singh and Sharma2014) have been reassigned to C. kullingii by Liu and Moczydłowska (Reference Liu and Moczydłowska2019). Examples of Tonian C. kullingii are from the Svanbergfjellet and Draken formations of the Akademikerbreen Group in northeastern Svalbard (Knoll et al., Reference Knoll, Swett and Mark1991; Butterfield et al., Reference Butterfield, Knoll and Swett1994), the Fifteenmile Group in Northwest Canada (Allison and Awramik, Reference Allison and Awramik1989), and the Chuar Group in the Grand Canyon of the western U.S. (Vidal and Ford, Reference Vidal and Ford1985). Examples of Ediacaran Cymatiosphaeroides include C. kullingii from the Doushantuo Formation in South China (see Liu and Moczydłowska, Reference Liu and Moczydłowska2019, for details).

Cymatiosphaeroides forabilatus Liu and Moczydłowska, Reference Liu and Moczydłowska2019, emend. Shang et al., Reference Shang, Liu and Moczydłowska2019
Figures 20–22

Reference Tiwari and Azmi1992

Form B, Tiwari and Azmi, p. 390, pl. 1, fig. 15.

Reference Tiwari and Knoll1994

Ericiasphaera spjeldnaesii Vidal, Reference Vidal1990; Tiwari and Knoll, p. 198, pl. 1, fig. 1 (part).

Reference Tiwari and Knoll1994

Unclassified acanthomorphic acritarch; Tiwari and Knoll, p. 198, pl. 1, fig. 6.

Reference Shukla and Tiwari2014

Unnamed Form E; Shukla and Tiwari, p. 222, fig. 7E–G.

Reference Liu and Moczydłowska2019

Cymatiosphaeroides forabilatus Liu and Moczydłowska, p. 81, fig. 41.

Reference Shang, Liu and Moczydłowska2019

Cymatiosphaeroides forabilatus; emend. Shang et al., p. 22, figs. 9, 10A–C.

Figure 20. Cymatiosphaeroides forabilatus. (1–4) DH-14-67.0-C, 11.8 × 139.0, EF-Q39-1, VPIGM-4848, white rectangle in (1) marks area shown in (2) at a different focal level, and black rectangle in (1) marks area shown in (3, 4) at two different focal levels; (5–7) DH-14-67.0-C-2, 12.0 × 135.9, EF-Q36-3, VPIGM-4852, rectangle in (5) marks area shown in (6) at a different focal level, and arrow in (6) marks area shown in (7) at a different focal level and with a rotation; (8–11) DH-14-67.0-C-2, 15.2 × 137.3, EF-N37, VPIGM-4854, white and black rectangles in (8) mark areas shown in (9) and (11), respectively, and arrow in (9) marks area magnified in (10).

Figure 21. Cymatiosphaeroides forabilatus. (1–4) DH-14-67.0-B-2, 12.5 × 136.7, EF-P37-3, VPIGM-4846, rectangle in (1) marks area shown in (2), and arrow in (2) marks area shown in (3, 4) at different focal levels; (5–7) DH-14-67.0-C-2, 15.3 × 137.7, EF-M37-3, VPIGM-4855, rectangles in (5, 6) mark areas shown in (6, 7), respectively; (8–10) S4-4-F2-5, 8.4 × 128.8, EF-U29-1, VPIGM-4876, white and black rectangles in (8) mark areas shown in (9, 10), respectively, at a different focal levels.

Figure 22. Cymatiosphaeroides forabilatus. (1–3) S4-4-F2-15, 10.3 × 129.7, EF-S30-1, VPIGM-4898, rectangle in (1) marks area shown in (2) with 180° rotation, and arrow in (2) marks area shown in (3); (4, 5) S4-4-F2-15, 22.3 × 106.4, EF-F6, VPIGM-4902, rectangle in (4) marks area shown in (5); (6, 7) S4-4-F2-14, 22.8 × 134.7, EF-E34-4, VPIGM-4897, arrow in (6) marks area shown in (7); (8–10) S4-4-F2-9, 16.4 × 135.5, EF-M35, VPIGM-4895, rectangle in (8) marks area shown in (9), and arrow in (9) marks area shown in (10).

Holotype

IGCAGS–D2XFH212, thin section XFH0946-1-10, reposited at the Institute of Geology, Chinese Academy of Geological Sciences, from member II of the Ediacaran Doushantuo Formation at Xiaofenghe section in the Yangtze Gorges area, Hubei Province, South China (Liu and Moczydłowska, Reference Liu and Moczydłowska2019, fig. 41A, B).

Occurrence

Ediacaran of South China and northern India. South China: member II of Doushantuo Formation at northern and southern Xiaofenghe sections, Yangtze Gorges area, Hubei Province (Liu and Moczydłowska, Reference Liu and Moczydłowska2019); Doushantuo Formation at Liujing section in Guizhou Province (Shang et al., Reference Shang, Liu and Moczydłowska2019). Northern India: Krol A Formation, Solan area (this paper).

Description and measurements

Large double-walled spheroidal vesicles with densely and evenly distributed processes. Processes arise from the inner wall and penetrate the outer wall. They are thin, short, uniform in length, and basally separate. Processes are apparently solid at the distal end, but many of them are hollow at least at the base, with a small basal expansion tapering distally toward a thin filament (e.g., Fig. 20.2–20.4). Vesicle diameter ~315–430 μm (estimated from Fig. 20.1, 20.5, 20.8), 28–41 processes per 100 μm of vesicle periphery, process length 6–10 μm (~1.5–2.4% of vesicle diameter), process spacing 1–3 μm at base, basal expansion (when discernable) 1–2 μm wide at base and 1–2 μm in height, apical spine ~0.5–0.9 μm wide and 5–7 μm long. Inner and outer walls ~5 μm apart.

Remarks

The Krol A specimens are identified as Cymatiosphaeroides forabilatus based on their double-walled vesicles that bear processes arising from the inner wall and penetrating the outer wall. Processes are extremely thin and it is difficult to determine whether they are solid or hollow. However, in several better-preserved specimens, it can be seen that the processes have a small basal expansion and is hollow at least at the basal part (e.g., Fig. 20.2–20.4). Shang et al. (Reference Shang, Liu and Moczydłowska2019) also noted that the processes of C. forabilatus are “slightly widened at the bases” in some specimens and that they are hollow in nature.

The specimen illustrated in Figure 22.8–22.10 is strongly degraded and obscured by the accumulation of organic matter. Nonetheless, remnants of processes extruding beyond the outer wall can be seen in the upper left of Figure 22.10. Thus, we regard this specimen as a poorly preserved example of C. forabilatus.

In sharp contrast to Cymatiosphaeroides kullingii, which has an extremely long stratigraphic range, C. forabilatus is restricted to the Ediacaran based on biostratigraphic data available thus far. Indeed, this is one of the common species in the Ediacaran Doushantuo Formation in South China and Infra-Krol–Krol A formations in northern India. Several previously published specimens from the Infra-Krol–Krol A formations are characterized by large double-walled vesicles with thin processes arising from the inner wall and penetrating the outer wall. These specimens are similar to the specimens described here in vesicle size, process length and width, and spacing between double walls, and some of them have a small expansion at the base of the processes (e.g., Shukla and Tiwari, Reference Shukla and Tiwari2014). These specimens include (1) Form B in Tiwari and Azmi (Reference Tiwari and Azmi1992), which was subsequently described as Ericiasphaera spjeldnaesii in Tiwari and Knoll (Reference Tiwari and Knoll1994); (2) Unclassified acanthomorphic acritarch in Tiwari and Knoll (Reference Tiwari and Knoll1994), which was later assigned to Tianzhushania spinosa (Zhang et al., Reference Zhang, Yin, Xiao and Knoll1998); and (3) Unnamed Form E of Shukla and Tiwari (Reference Shukla and Tiwari2014). These specimens are here considered to be Cymatiosphaeroides forabilatus. Additionally, specimens illustrated as Tianzhushania spinosa (Shukla et al., Reference Shukla, Mathur, Babu and Srivastava2008, pl. 3, figs. 1, 2) and Echinosphaeridium maximum (Shukla et al., Reference Shukla, Mathur, Babu and Srivastava2008, pl. 2, figs. 13, 14) appear to have double-walled vesicles bearing processes that arise on the inner wall and penetrate the outer wall; these may also be C. forabilatus, but further examination is needed to verify this suspicion because the specimens are poorly preserved.

Type species

Dictyotidium dictyotum Eisenack, Reference Eisenack1955

Other species

Two additional species have been reported from the Precambrian: Dictyotidium fullerene Butterfield in Butterfield et al. (Reference Butterfield, Knoll and Swett1994) from the Tonian Algal Dolomite Member of the Svanbergfjellet Formation at Geerabukta of Spitsbergen, and Dictyotidium ambonum Zang in Zang and Walter (Reference Zang and Walter1992) from the Ediacaran Pertatataka Formation at Rodinga 4 drill core in Amadeus Basin, central Australia. Other species are listed in Eisenack et al. (Reference Eisenack, Cramer and Díez1979) and Fensome et al. (Reference Fensome, Williams, Barss, Frerman and Hill1990).

Holotype

VPIGM-4832, thin section DH-14-65.0-A-2, Olympus BX-51 coordinates 10.6 × 108.8, England Finder coordinates R9-3, illustrated in Figure 23.1–23.5, reposited in Museum of Geosciences at Virginia Tech, from Krol A Formation in Solan area, Lesser Himalaya, northern India.

Figure 23. Dictyotidium grazhdankinii Xiao new species. (1–5) Holotype, DH-14-65.0-A-2, 10.6 × 108.8, EF-R9-3, VPIGM-4832, arrow in (1) marks area shown in (2–4) at different focal levels, and arrow in (3) marks area magnified in (5); (6, 7) S4-4-F2-5-2, 11.9 × 128.5, EF-Q28-4, VPIGM-4881, arrow in (6) marks area magnified in (7).

Diagnosis

A species of Dictyotidium with a delicate network consisting of polygonal reticular fields that are 1–5 μm in dimension and defined by thin ridges 0.2–1.0 μm in thickness. No processes are present.

Occurrence

Ediacaran Krol A Formation in the Solan area, Lesser Himalaya, northern India (this paper).

Description and measurements

Medium-sized to large vesicles consisting of a reticulate framework with apparent absence of a continuous vesicle wall. Vesicle diameter 100–400 μm (holotype 120 μm, Fig. 23.1). Polygonal fields 1–5 μm in size (2–4 μm in holotype, Fig. 23.2–23.5). Ridges 0.2–1.0 μm in thickness (0.2–0.4 μm in holotype, Fig. 23.5).

Etymology

In recognition of Dr. Dmitriy Grazhdankin's contributions to Ediacaran paleontology and his service to the Ediacaran Subcommission.

Remarks

One may argue that the reticulate pattern of the Krol A specimens is a result of degradation or taphonomic alteration of the vesicle wall. For example, recrystallization of quartz crystals may displace and concentrate organic residues along crystal interfaces to form polygonal crystal rings (Brasier et al., Reference Brasier, McLoughlin, Green and Wacey2006). There is no doubt that Krol A fossils have been subjected to taphonomic processes, including alteration related to crystal growth. This can be seen in numerous cases of discontinuous carbonaceous particles that outline microfossil structures (e.g., processes of Appendisphaera? hemisphaerica, Fig. 8.10). However, close examination of the best-preserved specimens, here identified as Dictyotidium grazhdankinii Xiao n. sp., led us to believe that their reticulate pattern is not a taphonomic artifact. First, observation under cross-polarized light microscopy shows that the fossils are replicated by microcrystalline silica and the reticulate pattern does not match any crystal extinction pattern when observed under crossed nicols. Second, microscopic observation by adjusting the focal level confirms that the organic ridges are one-dimensional thread-like structures that are relatively continuous, uniform in thickness, and weaved into a reticulate sheet (Fig. 23.2–23.4). Importantly, when the fossil is deformed, the reticulate sheet is also folded accordingly, without any disruption of the reticulate pattern (Fig. 23.2–23.4). These observations are in sharp contrast to polygonal crystal rings (Brasier et al., Reference Brasier, McLoughlin, Green and Wacey2006) that form three-dimensional spongy networks consisting of discontinuous carbonaceous particles distributed along crystal interfaces and often are concentrated at multi-crystal junctions (where incongruent crystal morphologies result in open space where organic matter accumulates). Thus, for the best-preserved specimens (e.g., Fig. 23.1–23.5), the regular reticulate morphology is unlikely a taphonomic artifact. In some specimens, parts of the vesicle show a regular reticulate sheet, whereas the other parts have more degraded patterns (e.g., Fig. 23.6, 23.7); these are interpreted as Dictyotidium grazhdankinii Xiao n. sp. specimens that have been unevenly altered by taphonomic processes.

Herkomorphs are acritarchs with their vesicle walls divided into polygonal fields. Examples include Cymatiosphaera Wetzel, Reference Wetzel1933; Dictyosphaera Xing and Liu, Reference Xing and Liu1973; Dictyosphaeridium Wetzel, Reference Wetzel1952; and Dictyotidium Eisenack, Reference Eisenack1955. In Cymatiosphaera, the polygonal fields are defined by fence-like structures perpendicular to the vesicle wall, thus distinct from the reticulate ridges in the Krol A specimens. In the other three genera, the polygonal fields are defined by ridges on the vesicle wall (typically manifested as polygonal platelets in Dictyosphaera; Agić et al., Reference Agić, Moczydłowska and Yin2015). However, Dictyosphaeridium bears processes, and Dictyosphaera may represent a different ontogenetic stage of the acanthomorphic herkomorph Shuiyousphaeridium Yan in Yan and Zhu, Reference Yan and Zhu1992 (Xiao et al., Reference Xiao, Knoll, Kaufman, Yin and Zhang1997; Agić et al., Reference Agić, Moczydłowska and Yin2015). Thus, given its lack of processes, the Krol A specimens are best referred to the genus Dictyotidium.

Dictyotidium grazhdankinii Xiao n. sp. can be distinguished from the other Ediacaran species of Dictyotidium (D. ambonum Zang in Zang and Walter, Reference Zang and Walter1992) by its larger overall size but smaller reticulum size, as well as its apparent lack of a continuous vesicle wall. It is similar to the Tonian species D. fullerene Butterfield in Butterfield et al. (Reference Butterfield, Knoll and Swett1994) in that both taxa apparently lack a continuous vesicle wall. However, D. fullerene has short processes at the corners of polygonal fields and has thicker and more robust ridges. The apparent lack of a continuous vesicle wall is probably a taphonomic artifact; perhaps the vesicle wall was thin and had been preferentially degraded.

A specimen illustrated as “reticulate acanthomorphic acritarch” from the upper Ediacaran or Cambrian Oppokun Formation in north-central Siberia (Grazhdankin et al., Reference Grazhdankin, Nagovitsin, Golubkova, Karlova, Kochnev, Rogov and Marusin2020) also has a vesicle consisting of a reticulate network, and is similar to Dictyotidium grazhdankinii Xiao n. sp. in vesicle size, reticulum size, and ridge thickness. However, the Oppokun specimen seems to have minute and faintly preserved processes.

Type species

Mengeosphaera chadianensis (Chen and Liu, Reference Chen and Liu1986) Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014.

Other species

Mengeosphaera angusta Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; M. bellula Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; M. constricta Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; M. eccentrica Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014; M. flammelata Liu and Moczydłowska, Reference Liu and Moczydłowska2019; M. gracilis Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; M. grandispina Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; M. latibasis Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; M. lunula Liu and Moczydłowska, Reference Liu and Moczydłowska2019; M. matryoshkaformis Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021; M. membranifera Shang et al., Reference Shang, Liu and Moczydłowska2019; M. minima Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; M. reticulata (Xiao and Knoll, Reference Xiao and Knoll1999) Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014; M. spinula Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; M. stegosauriformis Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; M. uniformis Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014.

Remarks

The genus Mengeosphaera is characterized by closely and evenly arranged biform processes (Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014). However, the definition of biform processes varies. According to Grey (Reference Grey2005, p. 175), a biform process has “a conical base and tapering or ciliate distal portion.” Following this definition, a gradually tapering process (e.g., in Tanarium conoideum Kolosova, Reference Kolosova1991; see simplified diagrams in Fig. 24.2–24.4) would be regarded as biform. Subsequently, a biform process was defined as a process with “a basal expansion and an apical spine or lateral spine, often separated by an inflection point” (Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014, p. 4), emphasizing the distinct and recognizable boundary between the basal and apical parts of the process (Fig. 24.5–24.10). An inflection point can represent a gradual transition from an inflated basal expansion to a distally tapering or cylindrical apical spine (e.g., Fig. 24.5). This is analogous to the mathematical inflection point where a convex curve changes to a concave curve and where the second derivative of the curve is zero (or where the distally decreasing slope of the inflated basal expansion transitions to the distally increasing slope of the deflated apical spine). From a practical point of view, an inflection point of a biform process also can represent an abrupt change in slope between the basal expansion and apical spine, regardless of whether the basal expansion is inflated (Fig. 24.6–24.10). In contrast, a process with a concave (or deflated) basal expansion continuing into an apical spine without an inflection point in between is not regarded as a biform process (Fig. 24.2–24.4), even if it would fit the definition of Grey (Reference Grey2005).

Figure 24. Schematic illustration of non-biform (1–4) and biform processes (5–10). Arrows point to inflection points in biform processes.

The genus Mengeosphaera was diagnosed by its biform processes with a conical or domical, often inflated, basal expansion that tapers rapidly and supports an apical spine that is acutely conical, often very thin, and tapers gradually (Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014). An inflection point separates the basal expansion and apical spine. This feature is best seen in the holotype of the type species, Mengeosphaera chadianensis (Chen and Liu, Reference Chen and Liu1986). Xiao et al. (Reference Xiao, Zhou, Liu, Wang and Yuan2014) described two additional species of Mengeosphaera, M. reticulata and M. eccentrica, both of which are characterized by biform processes.

Liu and Moczydłowska (Reference Liu and Moczydłowska2019) commented that the inflated basal expansion of Mengeosphaera processes could be a taphonomic artifact unique to silica or phosphate mineralization, but not in shale preservation. We understand that an originally inflated basal expansion could become deflated due to degradation, contraction, and compression, regardless of preservation mode of mineralization and carbonaceous compression. However, it is difficult to understand how an originally deflated or otherwise non-inflated basal expansion would become consistently inflated during fossil mineralization, particularly when the basal expansion is preserved with structural integrity and show no evidence of organic displacement due to mineral recrystallization. Silicification or phosphatization is fundamentally a process of microcrystal precipitation on organic substrates, resulting in a mold and/or cast of the organic structure (Oehler and Schopf, Reference Oehler and Schopf1971; Xiao and Tang, Reference Xiao and Tang2022). Organic structures such as basal expansions can be preserved with structural integrity when they are coated with or embedded in phosphate and silica. If they are disintegrated or destroyed by mineral recrystallization, organic walls or membranes would be disrupted to form irregular structures. It is unlikely for a deflated basal expansion to become consistently inflated during mineralization/recrystallization and to still maintain its structural integrity.

Liu and Moczydłowska (Reference Liu and Moczydłowska2019) further stated that neither M. reticulata nor M. eccentrica have biform processes. They did not define what they meant by biform processes. Following either of the definitions of Grey (Reference Grey2005) or Xiao et al. (Reference Xiao, Zhou, Liu, Wang and Yuan2014), as clarified above and schematically illustrated in Figure 24, it is indisputable that all three species of Mengeosphaera described in Xiao et al. (Reference Xiao, Zhou, Liu, Wang and Yuan2014) have biform processes with clear inflection points. This key feature is clearly present in the holotypes of M. chadianensis, M. reticulata, and M. eccentrica, illustrated in Chen and Liu (Reference Chen and Liu1986, pl. 2, figs. 2, 4), Xiao and Knoll (Reference Xiao and Knoll1999, fig. 11H), and Xiao et al. (Reference Xiao, Zhou, Liu, Wang and Yuan2014, fig. 26.1), respectively. It should be pointed out that these holotypes are all three-dimensionally phosphatized and acid-extracted specimens that were imaged using scanning electron microscopy so that the biform nature of the processes is best seen in lateral views, but not discernable in apical views. Additionally, the fragile apical spines may be abraded during taphonomic reworking or acid extraction, and they may not be retained at all if the specimens are preserved as internal molds (Xiao and Knoll, Reference Xiao and Knoll1999). Despite these complications, the processes in the holotypes of the above-mentioned species were clearly illustrated, with an inflection point separating an inflated basal expansion and an apical spine, although the distal part of the apical spine is often not intact.

Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a) established 13 new species of Mengeosphaera, four of which are discussed here because of their uncertain placement in this genus. Mengeosphaera? cuspidata has conical or even deflated basal expansions and, as a result, was published as an open nomenclature to acknowledge its uncertain placement in Mengeosphaera. This species was subsequently transferred to the genus Tanarium Kolosova, Reference Kolosova1991, becoming T. cuspidatum (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014) Liu and Moczydłowska, Reference Liu and Moczydłowska2019. Similarly, Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a) noted that the basal expansion of M. triangularis was not clearly inflated and this species was tentatively placed in the genus Mengeosphaera. This species also was transferred to the genus Tanarium and became T. triangulare (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014) Liu and Moczydłowska, Reference Liu and Moczydłowska2019, an orthographic correction of T. triangularis as spelled in Liu and Moczydłowska (Reference Liu and Moczydłowska2019, p. 143, 151). In the same paper, however, Liu and Moczydłowska (Reference Liu and Moczydłowska2019, p. 129) listed M. triangularis as an accepted species of Mengeosphaera, likely as an unintended error. Liu and Moczydłowska (Reference Liu and Moczydłowska2019) mentioned in passing that M. spicata Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014, is a junior synonym of M. constricta, but provided no explanation or justification. Although the holotypes of these two species are notably different in vesicle size, process density, process spacing, and the presence of a constriction at process base (compare fig. 56.1, 56.2 and fig. 64.1, 64.2 of Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a), we do acknowledge that there are specimens (e.g., Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a, fig. 58) that are morphologically transitional between the two holotypes. Thus, we tentatively follow the synonymization of these two species proposed by Liu and Moczydłowska (Reference Liu and Moczydłowska2019). Finally, the species M.? gracilis was placed in open nomenclature because, relative to other Mengeosphaera species, it has somewhat densely arranged processes with somewhat long and thin apical spines, which are features typically associated with species of Appendisphaera (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a). Liu and Moczydłowska (Reference Liu and Moczydłowska2019), however, removed the ambiguity in genus placement (although it was still listed as M.? gracilis in Liu and Moczydłowska, Reference Liu and Moczydłowska2019, p. 129), a proposition followed by subsequent authors (e.g., Shang et al., Reference Shang, Liu and Moczydłowska2019) and in this paper.

Mengeosphaera gracilis Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014
Figure 25

Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a

Mengeosphaera? gracilis Liu et al., p. 96, fig. 60.

Reference Liu and Moczydłowska2019

Mengeosphaera gracilis; Liu and Moczydłowska, p. 132, fig. 71.

Reference Shang, Liu and Moczydłowska2019

Mengeosphaera gracilis; Shang et al., p. 25, fig. 14F, G.

Reference Shang and Liu2020

Mengeosphaera gracilis; Shang and Liu, p. 158, fig. 6F–L.

Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021

Mengeosphaera gracilis; Ouyang et al., fig. 16K–M.

Figure 25. Mengeosphaera gracilis. (1–3) S4-4-F2-8-2, 12.2 × 108.2, EF-Q8-3, VPIGM-4894, black and white rectangles in (1) mark areas shown in (2, 3), respectively; (4, 5) S4-4-F2-14, 10.9 × 104.4, EF-S4-2, VPIGM-4896, arrow in (4) marks area shown in (5) at a different focal level; (6, 7) S4-4-F1-2, 18.3 × 102.8, EF-K3-3, VPIGM-4869, rectangle in (6) marks area shown in (7) at a different focal level; (8–10) S4-4-F1-4, 9.2 × 129.0, EF-T29-3, VPIGM-4872, white and black arrows in (8) mark areas shown in (9, 10), respectively, at different focal levels.

Holotype

IGCAGS–WFG–727, reposited at Institute of Geology, Chinese Academy of Geological Sciences, from the lower member III of the Ediacaran Doushantuo Formation at Wangfenggang section in the Yangtze Gorges area, Hubei Province, South China (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a, fig. 60.1, 60.2).

Occurrence

Ediacaran of South China and northern India. South China: member II of Doushantuo Formation at Wuzhishan (Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021), Jiuqunao, Nantuocun, Niuping, Wangfenggang, and northern and southern Xiaofenghe sections (Liu and Moczydłowska, Reference Liu and Moczydłowska2019), as well as member III of Doushantuo Formation at Wangfenggang, Niuping, Xiaofenghe, Baiguoyuan, Chenjiayuanzi, Dishuiyan, and Liuhuiwan sections, Yangtze Gorges area, Hubei Province (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a); lower Doushantuo Formation (probably equivalent to member II) at Tianping section, Hunan Province (Shang and Liu, Reference Shang and Liu2020); Doushantuo Formation at Liujing section in Guizhou Province (Shang et al., Reference Shang, Liu and Moczydłowska2019). Northern India: Krol A Formation, Solan area (this paper).

Description and measurements

Large spheroidal vesicles with densely and evenly distributed processes open to vesicle interior. Processes biform, with a conical to slightly inflated basal expansion supporting a thin and distally tapering apical spine. Vesicle diameter ~280 μm (Fig. 25.8), 13–18 processes per 100 μm of vesicle periphery, process length 6–14 μm (~5% of vesicle diameter, as estimated from specimen illustrated in Fig. 25.8), process spacing 1–3 μm at base, basal expansion 4–6 μm wide at base, and 3–4 μm in height, apical spine ~1 μm wide and 4–10 μm long.

Remarks

Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a) commented on the similarities and differences among M. gracilis, Cavaspina basiconica, and Appendisphaera? hemisphaerica, all of which are characterized by processes with a basal expansion supporting a thin apical spine. The processes of C. basiconica do not have an inflated basal expansion and typically are shorter than the two other species. Relative to M. gracilis, A.? hemisphaerica was said to have narrower and more-inflated basal expansion, as well as proportionally longer and more densely arranged processes. As discussed under A.? hemisphaerica, however, these two species may be synonymous. The specimen of M. gracilis illustrated in Shang and Liu (Reference Shang and Liu2020) is poorly preserved, with its biform processes barely visible; therefore its taxonomic identification is tentative.

Type species

Tanarium conoideum Kolosova, Reference Kolosova1991, emend. Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993.

Other species

Tanarium acus Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; T. araithekum Grey, Reference Grey2005; T. capitatum Liu and Moczydłowska, Reference Liu and Moczydłowska2019; T. cuspidatum (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014) Liu and Moczydłowska, Reference Liu and Moczydłowska2019; T. digitiforme (Nagovitsin and Faizullin in Nagovitsin et al., Reference Nagovitsin, Faizullin and Yakshin2004) Sergeev et al., Reference Sergeev, Knoll and Vorob'Eva2011; T. elegans Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; T. gracilentum (Yin in Yin and Liu, Reference Yin, Liu, Zhao, Xing, Ding, Liu, Zhao, Zhang, Meng, Yin, Ning and Han1988) Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021; T. irregulare Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993; T. mattoides Grey, Reference Grey2005; T. megaconicum Grey, Reference Grey2005; T.? minimum Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; T.? muntense Grey, Reference Grey2005; Tanarium obesum Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; T. paucispinosum Grey, Reference Grey2005; T. pilosiusculum Vorob'Eva, Sergeev, and Knoll, Reference Vorob'Eva, Sergeev and Knoll2009; T. pluriprotensum Grey, Reference Grey2005; T. pycnacanthum Grey, Reference Grey2005; T. triangulare (Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014) Liu and Moczydłowska, Reference Liu and Moczydłowska2019, an orthographic correction of T. triangularis as published in Liu and Moczydłowska (Reference Liu and Moczydłowska2019); T. tuberosum Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993; T. uniformum Liu and Moczydłowska, Reference Liu and Moczydłowska2019; T. varium Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014; T. victor Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014.

Remarks

Together with Appendisphaera and Mengeosphaera, Tanarium is one of the richly speciose genera of Ediacaran acanthomorphs. This is due to the very broad definition of this genus. For example, according to Moczydłowska et al.'s (Reference Moczydłowska, Vidal and Rudavskaya1993) emendation, Tanarium is an acanthomorph with hollow processes that are conical or cylindrical, tapering or rounded distally, simple or branching. A number of acanthomorphs—including Papillomembrana Spjeldnaes, Reference Spjeldnaes1963, and Xenosphaera Yin, Reference Yin1987 (see Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a)—would fit in this definition, in which case Tanarium would be rendered a junior synonym. Grey's (Reference Grey2005) emendation restricts Tanarium to acanthomorphs with heteromorphic processes longer than 20% of vesicle diameter. This restriction would exclude a few species, including T.? minimum and T. pilosiusculum Vorob'Eva et al., Reference Vorob'Eva, Sergeev and Knoll2009, from the genus of Tanarium. But even this restriction would still include Xenosphaera and its type species, X. liantuoensis Yin, Reference Yin1987, rendering Tanarium a junior synonym. It is probably time to split the genus Tanarium as currently recognized into several genera on the basis of, for example, process length and morphologies.

Moczydłowska and Nagovitsin (Reference Moczydłowska and Nagovitsin2012) listed Tanarium stellatum Nagovitsin and Faizullin in Nagovitsin et al., Reference Nagovitsin, Faizullin and Yakshin2004, as a junior synonym of T. tuberosum, and Liu and Moczydłowska (Reference Liu and Moczydłowska2019) listed Tanarium obesum Liu et al., Reference Liu, Xiao, Yin, Chen, Zhou and Li2014, as a junior synonym of T. tuberosum, but no explanation was provided to justify these synonymization proposals. Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a, p. 113) diagnosed T. obesum as a species of Tanarium “with a small to medium-sized vesicle covered with a moderate number of relatively large, acutely conical, and heteromorphic processes that occasionally bifurcate.” Additionally, T. obesum has more numerous, more closely arranged, and more acutely conical processes than does T. tuberosum. In this paper, we follow Liu et al. (Reference Liu, Xiao, Yin, Chen, Zhou and Li2014a) and treat T. obesum as a distinct species (see also Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021).

Tanarium cf. T. conoideum Kolosova, Reference Kolosova1991, emend. Moczydłowska, Vidal, and Rudavskaya, Reference Moczydłowska, Vidal and Rudavskaya1993
Figure 26

cf. Reference Kolosova1991

Tanarium conoideum Kolosova, p. 57, fig. 5.1–15.3.

cf. Reference Moczydłowska, Vidal and Rudavskaya1993

Tanarium conoideum; emend. Moczydłowska et al., p. 514, text-fig. 10C, D.

Figure 26. Tanarium cf. T. conoideum. S4-4-F2-7, 17.1 × 120.0, EF-L20-3, VPIGM-4888. (1) Specimen overview; (2–6) close-up views showing details of processes. White and black arrows in (1) mark areas magnified in (2) and (3–6) (same area at different focal levels), respectively. Arrows in (4, 5) mark possible biform processes with a basal expansion.

Occurrence

Ediacaran Krol A Formation, Solan area, Lesser Himalaya, northern India (this paper).

Description and measurements

A poorly preserved specimen with numerous long and conical processes. Estimated maximum vesicle diameter 247 μm (Fig. 26.1), process length up to 60 μm (~24% of vesicle diameter), and process basal width up to 7 μm. Some processes appear to be biform (Fig. 26.4, 26.5), with a basal expansion 14 μm wide and 8 μm high, supporting an apical spine 4 μm in basal width and 45 μm in length.

Remarks

The specimen is similar to the holotype of Tanarium conoideum in morphology and proportional length of processes (cf., Kolosova, Reference Kolosova1991, fig. 5.1, 5.2). It is about twice as large in vesicle diameter and its process density is greater than the holotype (although Kolosova, Reference Kolosova1991, illustrated another specimen of T. conoideum with a greater density of processes than in the holotype). Some processes in the current specimen appear to be biform in shape, a feature that is not present in the holotype. Alternatively, these apparently biform processes may be a taphonomic artifact; a torn and dislodged process with its base attached to a small piece of the vesicle wall may appear to be biform. On the other hand, Grey (Reference Grey2005) emended the diagnosis of the genus Tanarium to emphasize its heteromorphic (morphologically variable) processes that are longer than 20% of vesicle diameter. She also commented that the processes of the Australian specimens of T. conoideum have a conspicuously widened base (e.g., Grey, Reference Grey2005, fig. 212D), although she did not specifically describe their processes as biform. Considering the uncertainty about the biform nature of the processes in the only available specimen from the Krol A Formation, we tentatively place this specimen in an open nomenclature. An alternative taxonomic home for this specimen would be the genus Mengeosphaera, if its biform processes can be confirmed with better-preserved specimens that show the intact transition from process base to vesicle wall.

Tanarium digitiforme (Nagovitsin and Faizullin in Nagovitsin et al., Reference Nagovitsin, Faizullin and Yakshin2004) Sergeev et al., Reference Sergeev, Knoll and Vorob'Eva2011
Figure 27

Reference Nagovitsin, Faizullin and Yakshin2004

Goniosphaeridium digitiforme Nagovitsin and Faizullin in Nagovitsin et al., p. 13, pl. 2, figs. 4, 5.

Reference Vorob'Eva, Sergeev and Chumakov2008

Unnamed form with processes; Vorob'Eva et al., fig. 2h.

Reference Golubkova, Raevskaya and Kuznetsov2010

“Goniosphaeridium” digitiforme; Golubkova et al., pl. 4, fig. 3.

Reference Sergeev, Knoll and Vorob'Eva2011

Tanarium digitiformum (Nagovitsin and Faizullin in Nagovitsin et al., Reference Nagovitsin, Faizullin and Yakshin2004) Sergeev et al., p. 1006, fig. 7.6.

Reference Moczydłowska and Nagovitsin2012

Tanarium digitiformum; Moczydłowska and Nagovitsin, p. 19, fig. 8D–8F.

Reference Xiao, Zhou, Liu, Wang and Yuan2014

Tanarium digitiforme; Xiao et al., p. 53, Fig. 34.1–34.3.

Reference Yang, Pang, Chen, Zhong and Yang2020

Tanarium digitiforme; Yang et al., p. 7, fig. 2L–M.

Figure 27. Tanarium digitiforme (Nagovitsin and Faizullin in Nagovitsin et al., Reference Nagovitsin, Faizullin and Yakshin2004) Sergeev et al., Reference Sergeev, Knoll and Vorob'Eva2011. (1, 2) DH-14-68.0-A, 21.3 × 130.3, EF-G30-1, VPIGM-4859, arrow in (1) marks area shown in (2), showing obliquely cut processes; (3–8) DH-14-65.0-A, 16.7 × 109.9, EF-L10-3, VPIGM-4831, (3, 4) the same area at two different focal levels, black and white arrows in (3) mark areas shown in (5) and (7), respectively, and black and white arrows in (4) mark areas shown in (6) and (8), respectively.

Holotype and paratype

Holotype (specimen N2, preparation PN8/17-2, number 673; illustrated in Nagovitsin et al., Reference Nagovitsin, Faizullin and Yakshin2004, pl. 2, fig. 4) and paratype (PN8/4-17/7-3; illustrated in Moczydłowska and Nagovitsin, Reference Moczydłowska and Nagovitsin2012, fig. 8E) are reposited in the Central Siberian Geological Museum of the United Institute of Geology, Geophysics, and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.

Occurrence

Ediacaran of East Siberia, South China, and northern India. East Siberia: Ura Formation of the Zhuya-Lena area (Nagovitsin et al., Reference Nagovitsin, Faizullin and Yakshin2004; Vorob'Eva et al., Reference Vorob'Eva, Sergeev and Chumakov2008; Golubkova et al., Reference Golubkova, Raevskaya and Kuznetsov2010; Sergeev et al., Reference Sergeev, Knoll and Vorob'Eva2011; Moczydłowska and Nagovitsin, Reference Moczydłowska and Nagovitsin2012). South China: Doushantuo Formation at Weng'an, Guizhou Province (Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014) and Baizhu, Hubei Province (Yang et al., Reference Yang, Pang, Chen, Zhong and Yang2020). Northern India: Krol A Formation, Solan area (this paper).

Description and measurements

Medium-sized spheroidal vesicles with a moderate number of basally separate, digitate, hollow, and cylindrical to clavate processes that open to vesicle interior. Vesicle diameter up to 144 μm (Fig. 27.3), ~5 processes per 100 μm of vesicle periphery, process length at least 19–22 μm (~19% of vesicle diameter), process width 13–17 μm, and process spacing ~9 μm at base.

Remarks

The specimens available are poorly preserved. In particular, the full length of the processes is not captured in thin sections. Most processes are captured in transverse or oblique sections (Fig. 27.2, 27.6, 27.8), making them appear to be circular, elliptical, or conical (Fig. 27.1, 27.2, lower center of Fig. 27.3), but the axially cut processes are cylindrical (Fig. 27.5) or clavate (Fig. 27.7). Overall, the process size, morphology, and density, as well as the vesicle size, of the Krol A specimens match the diagnosis of Tanarium digitiforme. Alternatively, these specimens could be assigned to Papillomembrana boletiformis Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014, a taxon characterized by cylindrical processes with a bulbous or clavate termination. As noted above, Papillomembrana and the broadly defined Tanarium may be synonymous, and Xiao et al. (Reference Xiao, Zhou, Liu, Wang and Yuan2014) commented that some Doushantuo specimens of Papillomembrana compta Spjeldnaes, Reference Spjeldnaes1963, are better assigned to T. digitiforme. Indeed, P. compta has been recorded previously from the Infra-Krol Formation in the Nainital area of the Lesser Himalaya (Table 1). The Krol A specimens illustrated here, however, have relatively longer processes (~19% of vesicle diameter) than P. compta (6–8% of vesicle diameter) and P. boletiformis (~5% of vesicle diameter). In light of Grey's (Reference Grey2005) attempt to differentiate Tanarium from other acanthomorphs on the basis of process length, we choose to place the Krol A specimens under T. digitiforme.

Type species

Weissiella grandistella Vorob'Eva, Sergeev, and Knoll, Reference Vorob'Eva, Sergeev and Knoll2009.

Other species

Weissiella brevis Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014, emend. Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021.

Weissiella brevis Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014, emend. Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021
Figure 28

Reference Xiao, Zhou, Liu, Wang and Yuan2014

Weissiella brevis Xiao et al., p. 61, fig. 38.

Reference Shukla and Tiwari2014

Weissiella cf. grandistella; Shukla and Tiwari, p. 219, fig. 8A–E.

Reference Ouyang, Zhou, Guan and Wang2015

Weissiella cf. brevis; Ouyang et al., p. 221, pl. III, figs. 7–13.

Reference Ouyang, Zhou, Guan and Wang2015

Weissiella sp.; Ouyang et al., p. 221, pl. IV, figs. 8–13.

Reference Ye, Tong, An, Tian, Zhao and Zhu2015

Weissiella sp.; Ye et al., p. 50, pl. I, figs. 15–19.

Reference Sharma, Tiwari, Ahmad, Shukla, Shukla, Singh, Pandey, Ansari, Shukla and Kumar2016

Weissiella cf. grandistella; Sharma et al., fig. 4K (same as Shukla and Tiwari, Reference Shukla and Tiwari2014, fig. 8A).

Reference Ouyang, Zhou, Xiao, Chen and Shao2019

Weissiella sp.; Ouyang et al., fig. 10E–H.

Reference Liu and Moczydłowska2019

Weissiella grandistella; emend. Liu and Moczydłowska, p. 163, fig. 91A–E (part).

Reference Shang, Liu and Moczydłowska2019

Weissiella grandistella; Shang et al., p. 28, fig. 19A, B.

Reference Tian, Song, Ye, Hu, An, Zhao, Bottjer and Tong2020

Weissiella sp.; Tian et al., fig. 9K, L.

Reference Liu, Qi, Fan, Guo, Pei, Huang, Cheng, Bian, Liu, Zhao and Zhang2021

Weissiella grandistella; Liu et al., fig. 5.3, 5.5.

Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021

Weissiella brevis; emend. Ouyang et al., p. 40, figs. 6C, D, 23A–N.

Figure 28. Weissiella brevis. (1–4) DH-14-68.0-C-2, 23.8 × 112.6, EF-D12-4, VPIGM-4868, white and black arrows in (1) mark areas shown in (2) and (3, 4) (at two different focal levels). Black arrows in (2–4) mark cross-walls within processes. Note that arrows in (2, 3) are placed outside processes, and arrow in (4) is inside the process.

Holotype

VPIGM-4641 (WPB-3-4-4, 16.53132.6), reposited in the Museum of Geosciences at Virginia Polytechnic Institute, from unit 4A (probably equivalent to member II) of the Doushantuo Formation at Weng'an, Guizhou Province, South China (Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014, fig. 38.1).

Occurrence

Ediacaran of South China and northern India. South China: unit 4A (probably equivalent to member II) of Doushantuo Formation, Weng'an, Guizhou Province (Xiao et al., Reference Xiao, Zhou, Liu, Wang and Yuan2014); member II and equivalent strata of Doushantuo Formation at Zhangcunping (Ye et al., Reference Ye, Tong, An, Tian, Zhao and Zhu2015; Ouyang et al., Reference Ouyang, Zhou, Xiao, Chen and Shao2019; Tian et al., Reference Tian, Song, Ye, Hu, An, Zhao, Bottjer and Tong2020), Jiulongwan (Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021), Jinguadun (Ouyang et al., Reference Ouyang, Zhou, Guan and Wang2015, Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021), Wuzhishan (Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021), Xiaofenghe (Liu and Moczydłowska, Reference Liu and Moczydłowska2019), and Changyang (Liu et al., Reference Liu, Qi, Fan, Guo, Pei, Huang, Cheng, Bian, Liu, Zhao and Zhang2021), Hubei Province; Doushantuo Formation at Liujing, Guizhou Province (Shang et al., Reference Shang, Liu and Moczydłowska2019). Northern India: Krol A Formation, Solan area (Shukla and Tiwari, Reference Shukla and Tiwari2014; Sharma et al., Reference Sharma, Tiwari, Ahmad, Shukla, Shukla, Singh, Pandey, Ansari, Shukla and Kumar2016; this paper).

Description and measurements

Medium-sized spheroidal vesicle with numerous evenly distributed processes that open to vesicle interior. Processes are relatively short, slightly taper toward an often-truncated distal end. Process interior is subdivided by transverse cross-walls. Vesicle diameter ~160 μm (Fig. 28.1), ~6–7 processes per 100 μm of vesicle periphery, process length ~15 μm (~10% of vesicle diameter), process width ~15 μm at base, and process spacing ~3 μm at base. One or more cross-walls present in each process, with a spacing of ~6 μm between cross-walls.

Remarks

Liu and Moczydłowska (Reference Liu and Moczydłowska2019) proposed that Weissiella brevis be synonymized with W. grandistella. However, W. brevis has distinctly smaller vesicles and more numerous processes than W. grandistella. Importantly, W. brevis has proportionally smaller and shorter processes relative to its vesicle size. With more materials available, the distinction between these two species has become clearer, and we follow Ouyang et al. (Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021) in regarding these two species as separate taxa. The distinction is even more apparent if the truncated distal end of W. brevis processes is a result of taphonomic breakage, because more completely preserved processes of W. brevis are expanded both basally and terminally (Ouyang et al., Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021), which is substantively different from the conical and distally tapering processes of W. grandistella. Based on the distinction between W. brevis and W. grandistella, as outlined in Ouyang et al. (Reference Ouyang, Zhou, Xiao, Guan, Chen, Yuan and Sun2021), several specimens previously illustrated as W. grandistella (Liu and Moczydłowska, Reference Liu and Moczydłowska2019; Shang et al., Reference Shang, Liu and Moczydłowska2019; Liu et al., Reference Liu, Qi, Fan, Guo, Pei, Huang, Cheng, Bian, Liu, Zhao and Zhang2021), W. cf. W. grandistella (Shukla and Tiwari, Reference Shukla and Tiwari2014; Sharma et al., Reference Sharma, Tiwari, Ahmad, Shukla, Shukla, Singh, Pandey, Ansari, Shukla and Kumar2016), and Weissiella sp. (Ye et al., Reference Ye, Tong, An, Tian, Zhao and Zhu2015; Ouyang et al., Reference Ouyang, Zhou, Xiao, Chen and Shao2019; Tian et al., Reference Tian, Song, Ye, Hu, An, Zhao, Bottjer and Tong2020) are here considered as W. brevis.