Locality information

The Guanzhuang section is the type locality of the Pingliang Formation and located near Yindong, Guanzhuang, Kongtong District, ~8 km SW of Pingliang City, Gansu Province, China (35°29′32″N, 106°36′31″E, WGS 84; Fig. 1). This naturally exposed, ~90 m high, steep cliff is easily accessible and located alongside a small creek. Sedimentary rocks in the section are part of one of five sub-basins comprising the southwest Ordos Basin, which experienced several transitions in sedimentary facies throughout the Middle–Upper Ordovician (Chen et al., Reference Chen, Zhang, Wang, Goldman, Bergström, Fan, Finney, Chen, Chen, Bergström, Finney, Zhang, Fan, Chen, Goldman, Wang and Ma2017; Dai et al., Reference Dai, Qiang, Tian, Xi, Luo, Li, Liang, Wang and Li2019; Yang et al., Reference Yang, Loon, Jin, Jin, Han, Fan and Liu2019).

Figure 1. Geological map of the Pingliang region, Gansu Province, China (modified after Sun et al., Reference Sun, Yang, Dong, Yang, Peng and Zhao2020); inset map shows the location of the Ordos Basin.

Sediments at Guanzhuang were deposited in a carbonate platform-marginal slope environment, with deposition of Pingliang Formation interpreted to have occurred in a convergent-margin, back-arc setting in response to a series of tectonic events associated with the Qinling Orogeny (Wang et al., Reference Wang, Zhou, Wang, Zhang, Jing and Xing2015a, Reference Wang, Zhou, Wang, Jing and Zhangb; Yang et al., Reference Yang, Chen, Chen, Ding, Gao, Lei, Zhang, Shi and Tong2015; Zhang et al., Reference Zhang, Zhang, Zhao, Nie, Wang and Zhang2019). A few minor folds and faults can be observed, but the stratigraphy of the Ordovician succession is not significantly disrupted by tectonic activities.

Stratigraphic context

The Guanzhuang section is ~100 m thick. It overlies the Lower Ordovician Sandaogou Formation at its base and is unconformably overlain by the lower Permian Shanxi Formation (Fig. 2). It consists predominantly of limestone and shale with thin intercalations of sandstone, calcareous mudstone, and some debris flow deposits. A diverse assemblage of graptolites and conodonts extracted from shale and carbonate layers constrain the succession to the Sandbian, which is widely considered to represent the best example of the boundary between the Nemagraptus gracilis and C. bicornis biozones (Finney et al., Reference Finney, Bergström, Chen and Wang1999; Wang et al., Reference Wang, Bergström, Zhen, Chen and Zhang2013; Chen et al., Reference Chen, Zhang, Wang, Goldman, Bergström, Fan, Finney, Chen, Chen, Bergström, Finney, Zhang, Fan, Chen, Goldman, Wang and Ma2017).

Figure 2. Lithostratigraphy of the Pingliang Formation in the Guanzhuang section (modified after Wang et al., Reference Wang, Bergström, Zhen, Chen and Zhang2013) and correlation of biozones with co-occurring conodonts and graptolites. Scale bars are 100 μm where not specified.

Levels previously examined for radiolarians by Wang (Reference Wang1993) and Wang et al. (Reference Wang, Cheng and Zhang2010) are stratigraphically lower than those from which the two samples that produced the assemblage described herein were collected (see Fig. 2). Both previous studies on Pingliang radiolarians are from the N. gracilis Graptolite Biozone. Wang (Reference Wang1993) assigned a radiolarian fauna from bed 3 in the Pingliang section (after Chen et al., Reference Chen, Zhou, Li, Zou, Wang, Luo, Yao and She1984) to the Syndyograptus subzone of the N. gracilis Biozone. This 27.5 m thick unit begins 13 m above the base of the section. The conodont assemblage Pygodus anserinus, Periodan aculeatus Hadding, Reference Hadding1913, and Pygodus serra (Hadding, Reference Hadding1913) occurs in beds 2–8 (Wang, Reference Wang1993) representing the entirety of upper Darriwilian (Dw3) to lower Sandbian (Sa1). Co-occurring graptolites include N. gracilis and C. bicornis, which range through the Sandbian (Sa1 and Sa2) (Wang, Reference Wang1993). Although Chen et al. (Reference Chen, Zhou, Li, Zou, Wang, Luo, Yao and She1984) provided an account of graptolites and conodonts from bed 3, no age-specific taxa were included other than mentioning that bed 4 contains N. gracilis and P. anserinus. Later conodont and graptolite studies of the Guanzhuang section (Wang et al., Reference Wang, Bergström, Zhen, Chen and Zhang2013; Chen et al., Reference Chen, Zhang, Wang, Goldman, Bergström, Fan, Finney, Chen, Chen, Bergström, Finney, Zhang, Fan, Chen, Goldman, Wang and Ma2017; Dai et al., Reference Dai, Qiang, Tian, Xi, Luo, Li, Liang, Wang and Li2019) allow improved correlation of the radiolarian assemblage from bed 3, which can be assigned to the Sandbian (Sa1) N. gracilis Biozone. Wang et al. (Reference Wang, Cheng and Zhang2010) examined the basal section of the Guanzhuang succession and introduced the radiolarian genus Gansuceratoikiscum occurring within the Pygodus anserinus Conodont Biozone.

Remarks

The order Albaillellaria was introduced by Deflandre (Reference Deflandre and Grassé1953). Holdsworth (Reference Holdsworth1969b) revised the initial diagnosis to incorporate Ceratoikiscidae within the Albaillellaria. The order can be traced to the Ordovician with the earliest genus, Protoceratoikiscum Goto et al. (Reference Goto, Umeda and Ishiga1992). The basic skeletal framework of Albaillellaria is composed of three fundamental elements referred to as intersector, a-bar, and b-bar, which might differ in their length, position, or shape depending on the genus. These basic elements are clearly expressed in Albaillellidae and Ceratoikiscidae, while Follicucullidae display a reduced and simpler skeleton. Several authors have proposed a homologous relationship between Ceratoikiscidae and Albaillellidae that is explained via phylogenetic models reflecting the possibility of a common ancestor, possibly a primitive ceratoikiscid in the early Paleozoic (Foreman, Reference Foreman1963; Holdsworth, Reference Holdsworth1969a, Reference Holdsworthb; Won, Reference Won1983; Cheng, Reference Cheng1986; Renz, Reference Renz1988; Aitchison, Reference Aitchison1993). To accommodate all the genera from Ordovician to earliest Triassic that are presently assigned to this order, one should assume the initial skeleton of albaillellarians has undergone extensive modifications along the evolutionary pathway. De Wever et al. (Reference De Wever, Caulet, Nigrini and Caridroit2001) remarked, that during these skeletal alterations, albaillellarians were successful enough to always conserve at least one out of their three skeletal elements.

Remarks

Initially this family included Ceratoikiscum and Holoeciscus, but has now been expanded to include more than a dozen genera spanning from Ordovician–Carboniferous. Foreman (Reference Foreman1963) introduced the basic nomenclature to describe the skeletal elements of ceratoikiscids, which was elaborated on later by several authors (Holdsworth, Reference Holdsworth1969b; Renz, Reference Renz1988; Noble and Lenz, Reference Noble and Lenz2007) (see Fig. 3.1, 3.2). Throughout their evolution, an architecture involving three principal rods that might have slightly reshaped or suppressed is retained as the most conspicuous feature of the Ceratoikiscidae, compared to highly variable development of patagial tissue and/or caveal ribs. Wakamatsu et al. (Reference Wakamatsu, Sugiyama and Furutani1990) stated that modifications among the caveal ribs are better regarded as features of lower levels of classifications. However, even the indisputable most primitive species, Protoceratoikiscum clarksoni Danelian and Floyd, Reference Danelian and Floyd2001, recovered from the Middle to Upper Ordovician chert beds in Southern Uplands, Scotland, displays a characteristic ‘triangular structure’ made from two primary spines and a straight by-spine that closely resembles the basic architecture of the three principal rods.

Figure 3. (1) Nomenclature describing the structural details of Ceratoikiscum. (2) Anatomical notation of the frame of Ceratoikiscum. i.d = intersector (extratriangular) dorsal portion; i.t = intersector triangle forming portion; i.v = intersector (extratriangular) ventral portion; a.p = a-rod (extratriangular) posterior portion; a.t = a-rod triangle forming portion; a.a = a-rod (extratriangular) anterior portion; b.d = b-rod (extratriangular) dorsal portion; b.v = b-rod (extratriangular) ventral portion; b.t = b-rod triangle forming portion (after Holdsworth, Reference Holdsworth1969b).

Type species

Etymalbaillella yennienii Li, Reference Li1995 (BGIN 930311) from the Baijingsi, Qilian Mountains, China, by original designation.

Diagnosis

Conical radiolarians with the patagium developed into a latticed framework enveloping the sub-triangular initial skeleton made of a prominent intersector along with a-bar and b-bar blended into the lattice. Bears an open anterior end and may have projections attached to the a-bar and intersector. Emended from Li (Reference Li1995).

Remarks

Etymalbaillella was first assigned to the Albaillellidae by Li (Reference Li1995). Constituent species include E. renzii, E. toriterminalis, and E. yennienii that were first reported from Baijingsi, Qilian Mountains, China (Li, Reference Li1995). Etymalbaillella was later grouped with Proventocitum and reassigned under the Proventocitiidae (Aitchison, Reference Aitchison1998). Noble and Webby (Reference Noble and Webby2009) recovered E. yennienii from the Malongulli Formation in Australia. To reflect the uncertainty about this assignment and to highlight the need for further investigation, it was placed under incertae sedis at both the Order and Family level by Noble et al. (Reference Noble, Aitchison, Danelian, Dumitrica, Maletz, Suzuki, Cuvelier, Caridroit and O'Dogherty2017). Known occurrences are significant because they come from deep marine (Li, Reference Li1995) and shallow marine (Noble and Webby, Reference Noble and Webby2009) facies. Both have yielded well-preserved shells in spite of their delicate nature. With reference to observations based on specimens observed in this study, the authors disagree with the comments of Noble and Webby (Reference Noble and Webby2009) on the lack of two lateral rods mentioned by Li (Reference Li1995) and the absence of albaillellid symmetry. In his discussion of the genus, Li (Reference Li1995, p. 338) noted the existence of “two rods along dorsal and ventral shell walls” united by “trabeculaea of circumferential ridge.” The nomenclature he applied reflects a preference towards the family Albaillellidae.

Considering the extensive discussions of phylogeny and homologies between Albaillellidae and Ceratokiscidae (Holdsworth, Reference Holdsworth1969a, Reference Holdsworth1971; Won, Reference Won1983; Cheng, Reference Cheng1986; Renz, Reference Renz1988; Aitchison, Reference Aitchison1993), both the aforementioned families undeniably share an architecture involving three principal rods, more or less modified depending on the context. The skeletal architecture that separates Ceratokiscidae and Albaillellidae is subtle, such that even a slight modification to the configuration can prompt confusion, which easily could make the case for a primitive morphotype. Therefore, emphasis should be placed on the stratigraphic continuity of forms when skeletal architecture is not obvious enough to proceed with a solid phylogenetic assignment. Cheng (Reference Cheng1986) remarked that acquisition of a shell, offset trabeculae on two rods, and wings, developed at a much later evolutionary stage. This explains the first occurrence of Albaillellidae in the Late Devonian (Cheng, Reference Cheng1986), while ceratokiscids made their entrance by the Middle Ordovician (Danelian and Floyd, Reference Danelian and Floyd2001). In spite of superficial resemblance of Etymalbaillella to Albaillella, there is little evidence to fill the stratigraphic gap between the first known occurrences of Albaillella and Etymalbaillella. This indicates the possibility of assigning Etymalbaillella to the Ceratoikiscidae because it also shares the same three-rod architecture and is compatible with the period of origin. Nevertheless, the possibility of finding a morphotype intermediate between Albaillella and Etymalbaillella in the stratigraphic gap cannot be completely eliminated, in which case further family-level revision may be required.

Etymalbaillella toriterminalis Li, Reference Li1995
Figures 4, 11.5

Reference Li1995

Etymalbaillella toriterminalis Li, p. 338, pl. 2, figs. 12, 16.

Figure 4. Structural details highlighted using a micro-CT model of Etymalbaillella toriterminalis (SEES/140703-49-ET2). (1) Complete specimen of E. toriterminalis; (2) inflated top area of the shell; (3) view from the anterior end towards the apex highlighting the skeleton symmetry; (4) a-bar blended into the lattice shell (Ortho view); (5) b-bar blended into the lattice shell (Ortho view); (6) intersector (Ortho view); (7) diagonal configuration of interpore areas, possibly indicating traces of caveal ribs; (8) anatomical notation of frame with ventral side facing front; a.a = a-bar (anterior portion); b.d = b-bar (dorsal portion) b.v = b-bar (ventral portion); i.v = intersector (ventral portion). Scale bars = 100 μm.

Holotype

Neotype specimen no. SEES/140703-55-ET1 (Fig. 11.5) and SEES/140703-49-ET2 (digitized as Fig. 4 and Supplemental Data 1) from Sandbian limestone beds in the Pingliang Formation, Guanzhuang section, Gansu Province, China.

Diagnosis

Conical skeleton composed of a latticed framework supported by and merged into the three-rod ceratoikiscid architecture; intersector, a-bar, and b-bar. B-bar extends laterally forming extratriangular segments at ventral and anterior positions. Slightly inflated close to the point of convergence between a-bar and intersector. Emended from Li (Reference Li1995).

Description

Observations using micro-CT reveals important skeletal features that suggest possible phylogenetic affiliation to the Ceratoikiscidae or Albaillellidae. Careful segmentation of the E. toriterminalis skeleton reveals the presence of an almost straight intersector (Fig. 4.6) along with an a-bar (Fig. 4.4) and b-bar (Fig. 4.5) blended with the latticed shell that forms the fundamental initial skeleton in ceratoikiscids and albaillellids. Intersections of the intersector with the b-bar and the a-bar with the b-bar produce prominent extratriangular segments at ventral and anterior junctions, respectively (Fig. 4.8). Extensions of the b-bar beyond the shell frame have the appearance of a pair of wings and show a maximum length of 80 μm. A-bar shows a slightly offset branching and makes up the lattice frame along with 1–2 wing-like extensions that project outwards from the shell. These wing-like extensions from the a-bar are much shorter than dorsal and ventral portions of the b-bar (Fig. 4.8). The shell is slightly inflated close to the point of convergence between the a-bar and intersector, which could be a result of the tendency of the a-bars to curve when present in typical ceratoikiscid frames (Fig. 4.2). There are no conspicuous caveal ribs, but it may be assumed that they have been reduced in forming the lattice frame in conjunction with the patagium. The continuous diagonal inter-pore areas highlighted in Figure 4.7 also can be interpreted as residual traces of caveal ribs.

Pores in the lattice are sub-rounded to polygonal and are arranged diagonally in rows. These pores gradually reduce in size towards the posterior end of the intersector. Lattice meshwork may be considered a type of primitive equivalent to the patagium seen in Ceratoikiscidae, although patagial vanes or tissue cannot be resolved specifically. The vertical length of the entire conical shell made of the latticed framework is 225 μm, excluding the possibly broken apex. The widely open anterior end is 115 μm in diameter (Ø), but is less than 65 μm at the posterior end. All specimens encountered have open posterior ends, although they can be interpreted as broken ends possibly as a result of taphonomic conditions.

Remarks

This is the first report of E. toriterminalis after the initial discovery from Baijingsi, Qilian Mountains in China. The original type material (BGIN 930851) has been destroyed (Li Hongsheng personal communication, 2020, via Luo Hui), so a neotype (SEES/140703-55-ET1) is designated herein. Specimens are extremely delicate and frequently leave behind molds upon fragmentation. Use of the terms adopted herein to describe the structural details of the species follows the terminology and the definitions revised by Holdsworth (Reference Holdsworth1969b). For E. toriterminalis, the presence of ventral and anterior extratriangular segments indicates a bias towards Ceratoikiscidae, even if the aspect of stratigraphic continuation is overlooked. Etymalbaillella toriterminalis is relatively small in dimensions when compared to E. renzii. It is distinguished from E. yennienii by having longer maximum lengths for wings.

Holotype

Neotype specimen no. SEES/140703-49-ER1 (Fig. 11.10) from Sandbian limestone beds in the Pingliang Formation, Guanzhuang section, Gansu Province, China.

Figure 11. SEM images of radiolarians extracted from bed 5 of the Pingliang Formation, Guanzhuang section, Gansu, China. (1) Inanibigutta pinglianensis Wang, SEES/140703-55-IP1; (2) Oriundogutta bella Wang, SEES/140703-55-OB1; (3) ?Oriundogutta miscella minuta Wang, SEES/140703-55-OM1; (4) Kalimnasphaera pingliangensis n. sp., holotype, SEES/140703-55-KP1; (5) Etymalbaillella toriterminalis Li, neotype, SEES/140703-55-ET1; (6) Inanibigutta verrucula (Nazarov and Popov), SEES/140703-49-IV1; (7, 12) Geminusphaera kongtongensis n. gen. n. sp., (7) SEES/140703-55-GK3, (12) holotype, SEES/140703-55-GK1; (8) Haplotaeniatum implexa n. sp., holotype, SEES/140703-55-HI1; (9) Inanigutta complanata (Nazarov), SEES/140703-55-IC1; (10) Etymalbaillella renzii Li, neotype, SEES/140703-49-ER1; (11) Geminusphaera grandis n. gen. n. sp., holotype, SEES/140703-55-GG1; (13) Protopylentonema ordosensis n. sp., SEES/140703-49-PO1; (14) Inanigutta gansuensis Wang, SEES/140703-55-IG1; (15) Inanigutta quadrispinosa n. sp., holotype, SEES/140703-49-IQ1. Scale bar is 100 μm.

Diagnosis

Conical skeleton composed of a latticed framework supported by and merged into the three-rod ceratoikiscid architecture; intersector, a-bar, and b-bar. Downward-facing pair of wings extends from the upper section of the intersector and a-bar. Emended from Li (Reference Li1995).

Description

Conical lattice frame is at least 300 μm long, excluding the broken apex of the specimens. The anterior end is wide open with Ø = 112 μm. The apical section of the shell develops a pair of identical wing-like projections, facing downward, having an approximate length of 50 μm. The rest of the shell is devoid of wings, unlike E. toriterminalis and E. yennienii. Pores are polygonal and gradually reduce in size upon reaching the posterior section of the shell. Pore sizes at the anterior end are larger than those seen in other species of Etymalbaillella.

Remarks

A single specimen was recovered from the Pingliang Formation in the Guanzhuang section. The original type material (BGIN 930919) has been destroyed (Li Hongsheng personal communication, 2020, via Luo Hui), so a neotype (SEES/140703-49-ER1) is designated herein. The specimen is moderately well preserved and SEM observations are not of sufficient clarity to allow commenting on the initial skeleton configuration. Nevertheless, the presence of identical apical protrusions and a conical lattice frame allows confident identification. The emended diagnosis of the species is based on the initial skeletal details revealed through the micro-CT model constructed for E. toriterminalis and the SEM observations of E. renzii.

Type species

Gansuceratoikiscum guanzhuangensis Wang et al., Reference Wang, Cheng and Zhang2010 (pl. 1, fig. 11) from Pingliang Formation in the Guanzhuang section of the Gansu Province, China by original designation.

Holotype

Specimen in Wang et al. (Reference Wang, Cheng and Zhang2010, pl. 1, fig. 11) from limestone beds in the Pingliang section, Gansu Province, China.

Description

Specimen 1 in Figure 12 appears to have the patagial tissue, a-bar, and b-bar, while specimens in Figure 12.3 and 12.4 display different numbers of caveal ribs originating from the a-bar. The specimen in Figure 12.2 could be a juvenile form with all three rods, a row of arch, and a median bar (sensu Wang et al., Reference Wang, Cheng and Zhang2010).

Remarks

Specimens recovered are most likely to be fragments of G. guanzhuangensis. Proholoeciscus foremanii reported from Qilian Mountains, China (Li, Reference Li1995), which is now regarded as a nomina dubia (Noble et al., Reference Noble, Aitchison, Danelian, Dumitrica, Maletz, Suzuki, Cuvelier, Caridroit and O'Dogherty2017), may also be a fragment of G. guanzhuangensis because it appears similar to the specimen in Figure 12.3.

Type species

Bissylentactinia rudicula Nazarov, Reference Nazarov1975 (GIN. No. 4046-19) from the Egindinskaya series, Southern Urals, Northern Mugodzhars, Aitpaika River by original designation.

Holotype

Specimen (GIN 4333/22) from the Middle Ordovician, Bestamaksk Formation, SW foothills of Chingiz Range, eastern Kazakhstan (Nazarov and Popov, Reference Nazarov and Popov1980, pl. XV, fig. 2).

Remarks

The specimen encountered clearly demonstrates ‘grouped branching’ developing at a certain distance from the median point, which distinguishes this genus from other members of the Palaeoscenidiidae. Because the studied assemblage includes several fragments of members belonging to the Palaeoscenidiidae, identification of Bissylentactinia would be challenging, if not for the grouped apophyses. The type specimen of B. bifida illustrated by Nazarov and Popov (Reference Nazarov and Popov1980) differs from the material in this study in having slightly longer (224 μm) spines. The specimen illustrated does not fully capture the length of the two hetero-polar spines. Apophyses on two spines are also broken. This is the first report of B. bifida from the Ordovician since erection of this species by Nazarov and Popov (Reference Nazarov and Popov1980). The long stratigraphic gap existing between Darriwilian (Nazarov and Popov, Reference Nazarov and Popov1980) and Frasnian (Nazarov, Reference Nazarov1975) occurrences can now be reconciled with the intervening occurrence in the Sandbian reported herein.

Type species

Haplentactinia rhinophyusa Foreman, Reference Foreman1963 (USNM 640392) from the Norwalk 1 calcareous concretions of the Upper Devonian Huron Member of the Ohio Shale by original designation.

Haplentactinia baltica Nazarov in Nazarov and Nolvak, Reference Nazarov and Nolvak1983
Figure 5, Supplemental Data 2

Reference Nazarov and Popov1980

Haplentactinia sp. Nazarov in Nazarov and Popov, p. 55, pl. XVII, fig. 4.

Reference Nazarov and Nolvak1983

Haplentactinia baltica Nazarov in Nazarov and Nolvak, p. 5, pl. II, figs. 2–4.

Figure 5. Structural details highlighted using a micro-CT model for Haplentactinia baltica (SEES/140703-55-HB1). (1) Complete specimen; (2) inner shell with five spines attached; (3) lattice meshwork of the outer shell. Scale bars (1) 50 μm; (2, 3) 25 μm.

Holotype

Specimen (GIT 182-4), former no. GIN R2/5408, from the Upper Ordovician, Saunja Formation in Estonia (Nazarov and Nolvak, Reference Nazarov and Nolvak1983, pl. II, figs. 2–4).

Description

Micro-CT observations on specimen SEES/140703-55-HB1 reveal a clearly discernible outer shell, eccentrically positioned inner shell, and six primary spines that originate from the latter (Fig. 5.1). The point of origination of one of the spines cannot be clearly determined. The outer shell is polygonal and made of an irregular lattice developing from apophyses of the primary spines. Apophyses develop at variable distances from the inner shell and are interconnected laterally and obliquely, producing an intertwined mesh. Because of these interconnections, wide sub-circular and polygonal-shaped spaces (Ø ≈ 20 μm) develop on the outer shell (Fig. 5.3). The maximum outer shell Ø ≈ 138 μm. The inner shell is made of delicate ‘bandages’ (sensu Won and Iams, Reference Won and Iams2011) and cylindrical strands of varying thicknesses coalescing to form a spheroid with a maximum Ø = 45 μm (Fig. 5.2). The lengths of gently tapering spines vary between 80–140 μm. Slightly curved or straight spines are both present.

Remarks

The inner spicule mentioned in the species description of Nazarov and Nolvak (Reference Nazarov and Nolvak1983) was not observable in our scanned specimen. However, the inner shell is composed of thin cylindrical strands, which might be easily confused with a spicule. Only one specimen was found and the fair probability of the inner spicule not being preserved in it prevents further revision to the systematics of the species. The first encounter of this species is from the Ulkuntas Member, which is Hirnantian in age (Nazarov and Popov, Reference Nazarov and Popov1980; Aitchison et al., Reference Aitchison, Suzuki and O'Dogherty2017a). The Saunja Formation of Estonia where the type specimen was introduced is of Nabala Stage and coincides with the uppermost Sandbian. Although H. baltica was apparently a rare species in the Late Ordovician, the distribution in three isolated paleo-plates (Baltica, N. China, and Kazakh) terranes accounts for its successful dispersal.

Type species

Palaeoephippium bifurcum (UA 7155) from the Cape Phillips Formation type section, Cornwallis Island, N.W.T, Canada (Goodbody, Reference Goodbody1986, pl. 4, figs. 1–4).

Holotype

Specimen (UA 7166) from the Cape Phillips Formation, Cornwallis Island, N.W.T, Canada (Goodbody, Reference Goodbody1986, p. 144, pl. 4, figs. 9, 10).

Description

Six rays, three from each end of a median bar. One apical ray, one intermediate ray, and one basal ray positioned at each end, bifurcating at short distances from the median bar. All six rays terminate with sharp ends.

Remarks

One nearly complete specimen (Fig. 12.10) was encountered, together with several bifurcated fragments. Although Li (Reference Li1995) mentioned this genus on an occurrence chart, no figures or descriptions were provided.

Remarks

Species level identification is not possible because the specimens are highly fragmentary. However, spines with point- or bar-centered apical, intermediate or basal distribution, and subsequent bifurcation are most likely to be associated with Palaeoephippium. There is a close resemblance between the specimen (Fig. 12.8) and P. tricorne Goodbody illustrated in Goodbody (Reference Goodbody1986, fig. 6.1), which illustrates a fragment, indicating Figure 12.8 could also be P. tricorne. The specimen in Figure 12.7 has six rays, one of which is apical. Three short rays occupy an intermediate position, and the remaining two basal rays bifurcate at least twice before terminating with pointed ends. The intersection of these six rays is at a point rather than a median bar.

Figure 12. SEM images of radiolarians extracted from bed 5 of the Pingliang Formation in the Guanzhuang section, Gansu, China. (1–5) Gansuceratoikiscum guanzhuangensis SEES/140703-49-GG1–5; (6, 9, 10) Palaeoephippium radices Goodbody, (6) bifurcating fragments, SEES/140703-55-PR1, (9, 10) SEES/140703-49-PR1–2; (7, 8) Palaeoephippium spp., SEES/140703-55-PSP1–2; (11) Bissylentactinia bifida Nazarov and Popov, SEES/140703-55-BB1. Scale bar is 100 μm.

Type species

Protopylentonema ordosensis n. gen. n. sp. (SEES/140703-49-PO1) from the Pingliang Formation in the Guanzhuang section,, Gansu Province, China.

Diagnosis

Pylomate radiolarian with an initial skeleton in the form of five rays arranged in two nearly perpendicular planes. One regularly porous sub-spherical shell envelopes the rays. Rays may develop apophyses midway that coalesce to form a second perforated shell. A few thin beams originate from the second shell to penetrate the cortical shell as short or long conical spines. Simple circular pylome is positioned near one or two of the primary spines. Primary and secondary spines often develop buttresses on cortical shell. Few to numerous conical by-spines.

Occurrence

Darriwilian to Sandbian from Kazakhstan and China (Nazarov, Reference Nazarov1975; Nazarov et al., Reference Nazarov, Popov and Apollonov1975; Nazarov and Popov, Reference Nazarov and Popov1980; Wang, Reference Wang1993; herein).

Etymology

In the sense of ‘Primitive Pylentonema’

Remarks

Protopylentonema n. gen. is introduced in this study to include Ordovician pylomate forms possessing a distinctive spicular system that represent entactinarians. Constituent species include Protopylentonema insueta (Nazarov, Reference Nazarov1975), Protopylentonema aperta (Nazarov et al., Reference Nazarov, Popov and Apollonov1975), Protopylentonema rimata, (Nazarov and Popov, Reference Nazarov and Popov1980), and Protopylentonema ordosensis n. sp.. The original species descriptions for P. aperta, P. rimata, and P. insueta clearly state the presence of centrally positioned, nearly perpendicularly arranged five spines and in the case of P. rimata and P. insueta, the existence of a vague inner shell developed from apophyses (Nazarov, Reference Nazarov1975; Nazarov and Popov, Reference Nazarov and Popov1980). These features accord with the micro-CT model created for P. ordosensis; the type species of the new genus. Nazarov and Ormiston (Reference Nazarov and Ormiston1993) reassigned these species (P. aperta, P. rimata, and P. insueta) to the genus Cessipylorum. Subsequently, Noble and Webby (Reference Noble and Webby2009) revised the genus Cessipylorum and synonymized it with Kalimnasphaera. Micro-CT comparison of Protopylentonema ordosensis n. sp. and Kalimnasphaera pingliangensis n. sp. demonstrates this assignment is not appropriate and that the taxa described earlier by Nazarov (Reference Nazarov1975) and Nazarov and Popov (Reference Nazarov and Popov1980) are best placed within the new genus Protopylentonema.

Holotype

Specimen no. SEES/140703-49-PO1 (Fig. 11.13) and paratype SEES/140703-49-PO2 (digitized as Fig. 6 and Supplementary Data 3) in the micropaleontology collection of SEES-UQ. Known from Sandbian limestone beds in the Pingliang Formation, Guanzhuang section, Gansu Province, China.

Diagnosis

Pylentonemid radiolarian consisting of two sub-spherical shells and a five-rayed initial spicule; two bi-polar rays and three rays lying in a nearly perpendicular plane. All five rays pass through the two shells to form long tapering primary spines with buttresses on outer shell. One bi-polar ray, emerging as a primary spine, guards the circular pylome. Three secondary spines initiate at the inner sphere and form buttresses upon penetrating the outer shell. Few by-spines originate at the surface of the outer shell.

Occurrence

Sandbian from China (Wang, Reference Wang1993, and herein).

Description

Skeleton consists of two sub-spherical shells. Outer shell (Ø = 285 μm) comprises a regularly porous network with circular pores (Ø, 5–15 μm) (Fig. 6.5). Pore frames maintain a consistent thickness (5 μm), except at junctions and in the vicinity of spines. The initial skeleton consists of five rays that lie upon two nearly perpendicular planes. Two of the five rays are bi-polar and positioned on one plane. Three of the five rays are arranged on a plane nearly perpendicular to the other (Fig. 6.8). The micro-CT scan did not reveal the exact structure of the meeting point (sensu Won and Below, Reference Won and Below1999) because secondary infillings occupied the site. An element rendered partially transparent that is illustrated in Figure 6.8 shows a polyhedron floating at the middle of five rays. When the rays are projected inwards, two sets of rays create separate articulation points, suggesting the possibility of the presence of an intervening bar (Fig. 6.3). This feature is short and fits the definition of a micro-bar (sensu Won and Below, Reference Won and Below1999). Approximately 65 μm from the meeting point, rays develop apophyses that coalesce to form the delicate inner shell Ø = 125 μm (Fig. 6.1). The shell is sub-spherical and unevenly perforated with polygonal rims developed around pores of varying sizes. Rays attain a wider Ø before they grow beyond the inner shell. They convert to beams (Ø = 15 μm) and rise to the surface of the outer shell. A set of three thinner beams (Ø = 7–8 μm) initiates from pore-frame junctions of the inner shell (Fig. 6.1). These secondary beams also penetrate the surface of the external shell. Primary and secondary beams that convert to spines branch trichotomously or quadrachotomously just before interception with the outer shell (Fig. 6.7) and develop massive buttresses on the surface after penetration (Fig. 6.6). This imposes a slightly hexagonal shape to the outer shell as the six massive buttresses develop on the sphere (Fig. 6.5). The primary and secondary spines cannot be differentiated after surfacing and develop into distally tapering spines with lengths subequal to or slightly less than the shell Ø. Average Ø ≈ 45 μm near the base of a spine. The pylome (Ø = 55 μm) is generally sub-circular and has no rim (Fig. 6.2). It develops near one of the bi-polar rays that grows into a main spine. Since the pylome is commonly regarded as the posterior end of protozoans, the opposing main spine can be referred to as an apical spine (see Fig. 6.4). Very few short (35 μm), conical by-spines occur on pore frame junctions of the outer shell.

Figure 6. Structural details highlighted using micro-CT model for Protopylentonema ordosensis n. sp. (paratype, SEES/140703-49-PO2). S_P: primary spines initiating from initial spicule. S_S: secondary spines initiating from inner sphere. S_Py: spines associated with pylome. Red and green spheres are inserted to aid visualization; yellow arrows indicate relics of SP. (1) Inner sphere and distribution of primary spines (S_P) and secondary spines (S_S) relative to the initial skeleton; (2) structure of pylome; (3) five rays displaying two separate meeting points; (4) position of pylome; (5) surface orientation of primary and secondary spines imposing a hexagonal appearance to the shell; (6) buttressed primary spine located near pylome; (7) branching of spines at the intersection with outer shell; red arrows indicate quadrachotomous branching possibly with one branch broken; (8) initial skeleton showing five-rayed spicule arranged along two nearly perpendicular planes. Scale bars are (1–6) 50 μm; (7, 8) 25 μm.

Etymology

Named after the Ordos Basin, in which sediments of the Pingliang Formation were deposited.

Remarks

A micro-CT model demonstrates the role of the initial skeleton in creating the two shells. Because the model does not reveal the structure of the meeting point of rays, there is a possibility of having a point-centered, five-rayed spicule or a polyhedron (sensu Nazarov and Popov, Reference Nazarov and Popov1980) instead of the micro-bar. Nazarov et al. (Reference Nazarov, Popov and Apollonov1975) preferred the words ‘polyhedron’ and ‘hexahedron’ to describe the center structure of P. aperta and P. insueta. The number of secondary spines that develop on the inner or external shell along with shell dimensions can be used to differentiate between species of this genus, while five primary spines will be a constant.

Type species

Haplotaeniatum labyrintheum Nazarov and Ormiston, Reference Nazarov and Ormiston1993 (GIN 4679/33) from the Sakmarskaya Suite, Southern Urals by original designation.

Holotype

Specimen no. SEES/140703-55-HI1 (Fig. 11.8) and paratype SEES/140703-55-HI2 (digitized as Fig. 7 and Supplemental Data 4) in the micropaleontology collection of SEES-UQ. Known from Sandbian limestone beds in the Pingliang Formation, Guanzhuang section, Gansu Province, China.

Figure 7. Structural details highlighted using micro-CT model of Haplotaeniatum implexa n. sp. (SEES/140703-55-HI2), paratype. Red and green spheres are inserted to aid visualization. (1) Complete skeleton; (2) configuration of spines and the layers from which they originate; (3) original micro-CT image and the interpreted spiraliform arrangement of layers; (4) growth of secondary spines from the mesh; (5) pseudospongy mesh of the outer shell surface. Scale bars are (1–4) 50 μm; (5) 5 μm.

Diagnosis

Haplotaeniatumidae characterized by numerous spines emanating from a dense, pseudospongy outer shell made of more than two spirally arranged discontinuous layers around an eccentric proloculus. Three tapering spines directly originate from the proloculus while the secondary spines initiate subsequently from the layers developing at different levels from the apophyses of the primary spines. Several thin by-spines occupy the outer surface.

Occurrence

Sandbian from China (herein).

Description

The spherical skeleton of H. implexa revealed by micro-CT observations constitutes a small proloculus overlain by a pseudospongy mesh composed of few incomplete layers arranged in a vague spiraliform configuration (Fig. 7.3). At least two levels existing in the entangled meshwork exposed when the points of origin of a few secondary spines were projected back using a digital model. Slightly eccentric proloculus (Ø = 62 μm) is made of thin bars that coalesce to form an approximately spherical shape. Consequently, large polygonal spaces appear on the proloculus surface. Three of the numerous spines emanating from the outer shell originate directly from the proloculus (Fig. 7.2). They are approximately arranged in a single plane and have a Ø = 15 μm at the base where they penetrate the outer surface. They develop apophyses that subsequently give rise to discontinuous layers of meshwork (Fig. 7.4). The layers themselves produce secondary spines of slightly lesser base Ø = 8–13 μm. Pseudospongy outer shell develops small pores up to Ø = 5 μm (Fig. 7.5) and several by-spines with lengths up to 40 μm. The average outer shell Ø = 180 μm (Fig. 7.1). All spines taper distally imposing a thorny appearance to the entire specimen.

Etymology

From the Latin ‘implexa’ symbolizing the ‘entangled.’

Remarks

Micro-CT reveals that layers of H. implexa are not as widely spread as those of Haplotaeniatum albaensis Perera, Aitchison, and Nothdurft, Reference Perera, Aitchison and Nothdurft2020 (see Perera et al., Reference Perera, Aitchison and Nothdurft2020). All the spherical Haplotaeniatum species encountered from the Darriwilian Shundy Formation (Pouille et al., Reference Pouille, Danelian and Maletz2014) are larger in outer diameter compared to H. implexa. However, it closely resembles the disorderly interwoven mesh of Haplotaeniatum sp. B (Pouille et al., Reference Pouille, Danelian and Maletz2014) and both share numerous outer spines. Haplotaeniatum sp. B is distinguished from H. implexa by its larger Ø = 313–320 μm and wider spine bases (Ø = 20–25 μm). The thin spines and their bases differentiate Haplotaeniatum sp. C (Pouille et al., Reference Pouille, Danelian and Maletz2014) from H. implexa, although the spongy meshwork of both appears similar. The shell dimensions of Haplotaeniatum sp. A (Yi et al., Reference Yi, Yuan, Aitchison and Feng2018) apparently matches with our specimen, but is too poorly preserved to comment further. Because the spiraliform pattern seen in H. implexa is less prominent, the origination points of spines can be traced to locate the exact positioning of levels in the spiraliform arrangement (see Fig. 7.2). The initial diagnosis of Haplotaeniatum only incorporated species with spiraliform or concentric shells (Nazarov and Ormiston, Reference Nazarov and Ormiston1993). However, subsequent revisions to the genus by Won et al. (Reference Won, Blodgett and Nestor2002) included species with a labyrinthine arrangement ranging between distinctly layered to entirely non-layered. The specimen encountered can be confidently placed within Haplotaeniatum and the micro-CT model provides insight into the microstructure of the genus.

Type species

Geminusphaera kongtongensis n. sp. (SEES/140703-55-GK1) from the Pingliang Formation, in the Guanzhuang section Gansu Province, China.

Diagnosis

Inaniguttid radiolarians possessing two porous spherical shells and seven or more radially arranged primary spines originating from the inner sphere. Usually accompanied by several by-spines.

Occurrence

Sandbian from China (herein).

Etymology

Derived from Latin, ‘geminus-sphaera’ meaning ‘double-sphere.’

Remarks

Hitherto, generic classifications of members of the Inaniguttidae are based on a wide range of morphological features, including the number of spines, number of spheres, spacing between spheres, and their dimensions (Caridroit et al., Reference Caridroit, Danelian, O'Dogherty, Cuvelier, Aitchison, Pouille, Noble, Dumitrica, Suzuki, Kuwahara, Maletz and Feng2017; Noble et al., Reference Noble, Aitchison, Danelian, Dumitrica, Maletz, Suzuki, Cuvelier, Caridroit and O'Dogherty2017). The significance assigned to each of these aspects is still debated because some authors question their reliability after considering factors such as ontogeny and ecological stress (Noble and Aitchison, Reference Noble and Aitchison1995; Danelian and Popov, Reference Danelian and Popov2003; Suzuki, Reference Suzuki2006; Maletz, Reference Maletz2011; Trubovitz and Stigall, Reference Trubovitz and Stigall2018; Kachovich and Aitchison, Reference Kachovich and Aitchison2020). Micro-CT observation reveals the genus Geminusphaera n. gen. shares characteristics intermediate between Inanihella and Inanibigutta. Inanihella incorporates inaniguttids with two closely spaced porous spheres bearing numerous spines. The diagnosis of Inanihella further mentions the existence of an inner structure in the form of a spheroid (Ø = 45–55 μm) or its modification. This represents the initial skeleton of Inanihella. In addition, it is flexible toward forms with pylomes and furrowed main spines (Nazarov and Ormiston, Reference Nazarov and Ormiston1984; Nazarov, Reference Nazarov1988; Noble et al., Reference Noble, Aitchison, Danelian, Dumitrica, Maletz, Suzuki, Cuvelier, Caridroit and O'Dogherty2017). All these diagnostic features appear to be more compatible with Silurian morphotypes than those from the Ordovician (Nazarov and Ormiston, Reference Nazarov and Ormiston1984, Reference Nazarov and Ormiston1993; Siveter et al., Reference Siveter, Aitchison, Siveter and Sutton2007). However, several authors have assigned a few Ordovician species under Inanihella despite poor preservation that hinders precise identification. Inanihella (?) akzhala (Danelian and Popov, Reference Danelian and Popov2003) and I. bakanasensis Danelian and Popov, Reference Danelian and Popov2003 (reported by Danelian and Popov, Reference Danelian and Popov2003, and Maletz et al., Reference Maletz, Albanesi and Voldman2009) do not show any trace of an inner structure within the inner sphere. Inanihella penrosei (Ruedemann and Wilson, Reference Ruedemann and Wilson1936) described by Wang (Reference Wang1993) from the Pingliang Formation clearly shows the presence of a spheroid within the inner shell although the two spheres are not closely spaced as is typically seen in Silurian forms. Pouille et al. (Reference Pouille, Danelian, Ghobadi and Popov2013) assigned five species under Inanihella, of which only two have a spherical internal structure located within the two shells. Although the aforementioned encounters comply with the expected shell dimensions for Inanihella, the presence of an internal structure should be favored because it represents the initial skeleton. Failure to observe an initial skeleton because of poor preservation also suggests the possibility of the non-existence of any internal structure. Maletz and Bruton (Reference Maletz and Bruton2008) suggested the possibility of resorbing materials from inner spheres to form outer spheres during ontogeny. Meanwhile, Inanibigutta (Nazarov, Reference Nazarov1988) only recognizes two-sphered inaniguttids, with only six primary spines. Unlike Inanigutta, the number of spines on Inanibigutta is fixed (Noble et al., Reference Noble, Aitchison, Danelian, Dumitrica, Maletz, Suzuki, Cuvelier, Caridroit and O'Dogherty2017). The new genus Geminusphaera includes inaniguttids that are constructed from two distinct porous spheres and have seven or more primary spines.

Previous reports.—Maletz and Bruton (Reference Maletz and Bruton2008) reported an assemblage of 51 specimens that included inaniguttids with two to three spherical walls connected by beams and variable numbers of outer spines, which they referred to as Inanigutta sp. B. They suggested a revision to the Inaniguttidae, allocating all spumellarians with multiple spheres and spines under Inanigutta. Maletz and Bruton (Reference Maletz and Bruton2008, fig. 9F, G) illustrated two well-preserved specimens with two distinct spheres and multiple spines that could be incorporated within Geminusphaera n. gen. In these specimens, inner and outer sphere Ø = 140 μm and 70 μm, respectively, and the number of spines varies from 8–10. The description of characteristics of the mesh and the origination of spines are analogous to those of Geminusphaera n. gen., suggesting assignment to the new genus is appropriate. In combination, this extends the possible stratigraphic range of Geminusphaera n. gen. to the Darriwilian.

Helioentactinia? bakanasensis reported by Nazarov (Reference Nazarov1975) from Arenigian strata of the Ushkyzyl Formation (Zhylkaidarov, Reference Zhylkaidarov1999) was described from thin sections and has two shells and numerous spines. This material also could be allocated to the new genus because the sphere dimensions (115–169 μm, 86–131 μm) and species description align best with Geminusphaera n. gen. This would further extend the stratigraphic range of Geminusphaera n. gen. to at least the Lower Ordovician.

Holotype

Specimen no. SEES/140703-55-GG1 (Fig. 11.11) in the micropaleontology collection of SEES-UQ. Known from Sandbian limestone beds in the Pingliang Formation, Guanzhuang section, Gansu Province, China.

Diagnosis

Two spherical shells connected by at least eight primary spines originating from the inner sphere. Outer shell has no by-spines.

Occurrence

Sandbian from China (herein).

Description

Spherical outer shell and inner shell show average Ø = 318 and 125 μm, respectively. Two spheres are separated by a gap of ~70 μm. Rounded to oval pores of varying sizes (8–24 μm) cover the outer shell, while the inner shell pores are generally smaller. Primary spines start as beams with constant Ø ≈ 13 μm and traverse through the outer shell. All the primary spines are equal in length (180 μm) and taper gradually before terminating with pointed ends. Maximum spine Ø of 25 μm is maintained at the surface intersection with the outer shell. Interpore frames and the bases of spines are attached smoothly through direct continuations.

Etymology

From the Latin ‘grandis’ meaning large.

Remarks

Previously, many double shelled, multiple spine bearing inaniguttids were assigned to the genus Inanihella, despite controversies discussed under genus remarks. This species is easy to distinguish from G. kongtongensis n. gen. n. sp. owing to its larger shell dimensions. In addition, pores of G. grandis n. gen. n. sp. are rounded to oval, whereas pores of G. kongtongensis n. gen. n. sp. exhibit irregular shapes.

Holotype

Specimen no. SEES/140703-55-GK1 (Fig. 11.12); SEES/140703-55-GK2 (digitized as Fig. 8 and Supplemental Data 5); and paratype, SEES/140703-55-GK3 (Fig. 11.7), in the micropaleontology collection of SEES-UQ. Known from Sandbian limestone beds in the Pingliang Formation, Guanzhuang section Gansu Province, China.

Figure 8. Structural details highlighted using micro-CT model of Geminusphaera kongtongensis n. gen. n. sp. (SEES/140703-55-GK2). Red and green spheres are inserted to aid visualization. (1) Complete skeleton with nine spines; (2) cross-section showing the empty inner shell; (3) outer shell; (4) inner shell; (5) radial arrangement of spines; (6) spines penetrating the outer sphere; (7) lattice framework of the outer shell; (8) lattice framework of the inner shell. Scale bars are (1–6) 50 μm; (7, 8) 10 μm.

Diagnosis

Inaniguttid radiolarians with two spherical latticed shells bearing 8–10 tapering primary spines originating from the inner shell that penetrate out through the outer shell. Several short conical by-spines are present.

Occurrence

Sandbian from China (herein).

Description

Micro-CT observation reveals two concentric spherical shells joined through nine radial beams originating at the surface of the inner sphere (Fig. 8.2). Outer sphere average Ø =175 μm whereas the inner sphere averages 90 μm (Fig. 8.3, 8.4). Where spines are not generated or penetrating, shell thickness is maintained at ~6 μm. Both spheres display similar lattice framework with sub-circular to irregular-shaped pores with Ø ranging from 6–15 μm (Fig. 8.7, 8.8). Except at junctions, bars delimiting the pores of the outer sphere maintain a regular thickness (4–5 μm), although this is inconsistent when it comes to the inner sphere. Two spheres are positioned ~35 μm apart (Fig. 8.2). The scanned specimen has nine primary spines, but the number ranges from 8–10. These primary spines originate at the surface of the inner sphere and rise as radial beams until they penetrate the outer sphere (Fig. 8.6). They gradually start to taper after piercing the outer surface and grow to a maximum length of 85 μm (measured from the surface of outer sphere). The width of the primary spines is ~15 μm at their base, which equals the Ø they maintain at the base of inner sphere. No apophyses are developed on the spines. Few short conical by-spines <10 μm are present on the outer shell surface. No trace of any internal structure beyond the inner shell.

Etymology

Named after the Kongtong District in China where the type locality is situated.

Remarks

The specimens encountered are well preserved and abundant enough to be able to determine shell measurements with confidence. Although primary spines are radially arranged and suggest the possible presence of a centrally located structure (Fig. 8.5), the micro-CT model clearly shows the vacant inner shell and how beams have developed from the inner shell surface. Oriundogutta miscella miscella (Nazarov in Nazarov and Popov, Reference Nazarov and Popov1980) reported from Pingliang Formation has similar dimensions (140–180 μm) to the outer sphere of G. kongtongensis n. gen. n. sp. and a similar number of primary spines (8–12). Illustrations in Wang (Reference Wang1993) are light-microscopic images, and it is possible that an inner sphere was undetected during observations. In addition, both reports come from the same formation, which may mean that both morphotypes represent a single species.

Type species

Entactinosphaera aksakensis Nazarov, Reference Nazarov1975 (GIN 4333/1) from the Bestamak Formation, SW foothills of Chingiz Range, eastern Kazakhstan by original designation.

Holotype

Specimen (NIGPAS-R0066) from Pingliang Formation, Gansu Province, China (Wang, Reference Wang1993, pl. 5, fig. 2).

Remarks

Specimens figured as Inanibigutta pingliangensis in Wang (Reference Wang1991), which were recovered from the Pingliang Formation, were illustrated and named but not accompanied by a species description. Wang (Reference Wang1993) again used probably the same specimen figured in his 1991 study, added some more specimens, and formally introduced s.l. pinglianensis with a name, proper species description, and a designated holotype.

Danelian and Popov (Reference Danelian and Popov2003) tentatively assigned Inanibigutta pinglianensis to Triplococcus, assuming the bifurcated apophyses on the outer shell are relics of a third shell. However, the specimen illustrated in Figure 11.1 clearly shows the bifurcated apophyses cannot be extended as a third shell because these sets of apophyses do not grow equidistant from the outer shell on all six spines. Micro-CT models of Triplococcus in Kachovich and Aitchison (Reference Kachovich and Aitchison2020) demonstrate its unique morphology, allowing differentiation between the disputed forms. The structure inside the inner shell remains uncertain because all of the encountered specimens had an infilled interior. Co-occurring fossils and zircons (An et al., Reference An, Zhang and Xu1985; Wu et al., Reference Wu, Li, Hu and Gong2014; Yang et al., Reference Yang, Chen, Kang, Ma, Chen, Tao and Deliang2020) indicate that the Zhaolaoyu Formation in Shaanxi Province, from which I. pinglianensis was reported for a second time (Song et al., Reference Song, Cui, Hua and Wang2000), is Late Ordovician, likely Sandbian age. Therefore, I. pinglianensis can be regarded as a good Sandbian marker taxon, especially in shallow water facies.

Holotype

Specimen (GIN 4333/18) from the Middle Ordovician, Bestamak Formation, SW foothills of Chingiz Range, eastern Kazakhstan (Nazarov and Popov, Reference Nazarov and Popov1976, fig. 1d).

Remarks

According to the original species description, one out of the six spines is generally lengthier than the rest. However, the closest specimens that displayed matching sphere dimensions did not show significant variation in spine length. In addition, none of the spines on the specimens maintains a constant Ø throughout their length (Nazarov and Popov, Reference Nazarov and Popov1976). Most spines on the observed specimens are broken at mid-length. Wang (Reference Wang1993) and Danelian and Clarkson (Reference Danelian and Clarkson1998) reported Ø = 180–260 μm and 131 μm for outer sphere Ø, for which Nazarov and Popov (Reference Nazarov and Popov1976) reported Ø = 160–200 μm. Because inner and outer sphere dimensions of the observed specimens (average Ø = 74 μm and 177 μm) correspond well with the measurements given in the original publication (75–85 μm; 160–200 μm), and all five specimens encountered show similar dimensions, they are assigned to I. verrucula.

Type species

Entactinia unica Nazarov, Reference Nazarov1975 (GIN 4333/2) from Bestamak Formation, SW foothills of Chingiz Range, eastern Kazakhstan by original designation.

Diagnosis

Internal structure represented by a hollow, non-porous sphere Ø = 40–75 μm, rarely less, with four to six rays emanating from it at angles of ~110–120°. A single, thick, mostly porous, envelope of up to Ø = 350 μm. Emended from Nazarov (Reference Nazarov1988).

Remarks

Inanigutta was established to include species with a single shell, demonstrating six-spine geometry (Nazarov and Ormiston, Reference Nazarov and Ormiston1984). However, the diagnosis was emended to include taxa with four to five spines by Nazarov and Popov (Reference Nazarov and Popov1980) who encountered two specimens with four-spine symmetry from an Upper Ordovician formation in Central Kazakhstan. Nevertheless, Inanigutta predominantly consists of six-spined species and no subsequent studies have reported forms with four/five spines.

Holotype

Specimen (GIN 4333/29) from the Middle Ordovician, Bestamak Formation, SW foothills of Chingiz Range, eastern Kazakhstan (Nazarov, Reference Nazarov1975, pl. XX, fig. 8).

Remarks

Shell dimensions given in Nazarov and Popov (Reference Nazarov and Popov1980) are clearer than those in Nazarov (Reference Nazarov1975). With the exception of Wang (Reference Wang1993), no subsequent reports correspond exactly with original descriptions (outer shell; Ø = 190 μm and 175 μm, respectively, in Danelian and Floyd, Reference Danelian and Floyd2001, and Noble and Webby, Reference Noble and Webby2009). The dimensions given in Nazarov and Popov (Reference Nazarov and Popov1980) provide the basis for assignment of the observed specimens to I. complanata. Spine lengths of the studied specimens are slightly shorter, but the rest of the features align well within descriptions of Nazarov and Popov (Reference Nazarov and Popov1980). The structure of the initial skeleton from which the spines radiate is obscure.

Holotype

Specimen (NIGPAS-R0087) from the Middle Ordovician, Pingliang Formation, Gansu Province, China (Wang, Reference Wang1993, pl. 7, fig. 1).

Remarks

Although specimens in this study exhibit similar sphere dimensions, they seem to have more secondary spines than the type specimens of I. gansuensis Wang. However, this variation could be an artefact of SEM illustrations. No specimens have spine lengths >300 μm, although Wang (Reference Wang1993) indicated a range of 200–500 μm.

Holotype

Specimen SEES/140703-49-IQ1 (Fig. 11.15) and SEES/140703-55-IQ2 (paratype, digitized as Fig. 9 and Supplemental Data 6) from Sandbian limestone beds in the Pingliang Formation, Guanzhuang section, Gansu Province, China.

Figure 9. Structural details highlighted using micro-CT model of Inanigutta quadrispinosa n. sp. (paratype, SEES/140703-55-IQ2). Red sphere inserted to aid visualization. (1) Complete skeleton; (2) porous lattice of the outer shell; (3) ortho-slice showing the displaced ?microsphere and its present position within secondary infillings; (4) approximate tetrahedral arrangement and ?microsphere in its inferred original position. Scale bar is 100 μm in (1, 3, 4); 6 μm in (2).

Diagnosis

Inaniguttid radiolarians constructed with a single perfectly spherical lattice shell and four primary spines arranged at ~110° to one another. Primary spines are directed towards a centrally located initial structure, possibly a microsphere. Numerous conical by-spines are located on external surface.

Occurrence

Sandbian from China (herein).

Description

Micro-CT observations reveal the structural configuration of this inaniguttid is exclusively constructed with four spines and a single shell. A perfectly spherical external shell averages Ø = 190 μm and has a lattice arrangement with sub-circular to irregular-shaped pores (Fig. 9.1, 9.2). Maximum pore Ø ranges between 5–20 μm (Fig. 9.2). The surface of the external shell is occupied by numerous short conical by-spines up to 25 μm in length. Four rod-like primary spines with pointed tips penetrate the outer shell, maintaining an ~110° orientation to one another (Fig. 9.4). Primary spines originate from a slightly eccentrically located structure, perhaps a microsphere (Ø = 75 μm). Initial sections of spines lie within the shell with a Ø lesser than the outer sections and point towards the center attaining a long conical shape (Fig. 9.4). The Ø at the base of the primary spines on the shell surface is 20 μm and they extend a further 190–220 μm.

Etymology

From Latin ‘quadrispinosa’ referring to four spines.

Remarks

The structure of the internal element is unclear, although it vaguely suggests the presence of a microsphere. On orthoslices, the microsphere is dislocated and engulfed by secondary infillings (Fig. 9.3). The external shell is undamaged. Dimensions of the taxon described are similar to Inanigutta gansuensis Wang reported from the Pingliang Formation in the Guanzhuang section, although the latter has six rather than four spines. Wang (Reference Wang1993) described I. gansuensis using light-microscopic images and some of the documented specimens appear to have four-spine geometry. Inanigutta gansuensis also had been reported in two studies where SEM images were used for descriptions (Pouille et al., Reference Pouille, Danelian, Ghobadi and Popov2013; Perera et al., Reference Perera, Aitchison and Nothdurft2020). Both studies mention broken spines and do not report any six-spined specimens.

Type species

Kalimnasphaera maculosa Webby and Blom, Reference Webby and Blom1986 (AM.F 134783) from limestone breccia deposits of the Malongulli Formation of New South Wales, Australia, by original designation.

Diagnosis

Palaeoactinommid with a combination of either reticulate inner shell, porous medullary shell, and pylomate cortical shell or one double-layered reticulate inner shell and pylomate reticulate cortical shell enveloped in a loosely fenestrate outer shell preserved in varying degrees. More than three long, gently tapering, primary and secondary spines may originate from any level of the shell. Few to numerous by-spines occupy the space on cortical shell and between cortical and fenestrate shells if present. A fenestrate outer shell is only complete in areas where lateral spinules are linked to by-spines and main spines. Emended from Webby and Blom, Reference Webby and Blom1986.

Remarks

Dunham and Murphy (Reference Dunham and Murphy1976) first reported Kalimnasphaera as ‘sphaeroids’ from Upper Ordovician calcareous concretions in Nevada. Material from that locality was revisited by Renz (Reference Renz1990) following a second encounter of the same genus from Upper Ordovician Australian limestones where it was formalized as Kalimnasphaera (Webby and Blom, Reference Webby and Blom1986). Kalimnasphaera has been reported several times from Australia (Goto et al., Reference Goto, Umeda and Ishiga1992; Umeda et al., Reference Umeda, Goto and Ishiga1992; Noble and Webby; Reference Noble and Webby2009), Kazakhastan (Pouille et al., Reference Pouille, Danelian, Ghobadi and Popov2013), and China (Cao et al., Reference Cao, Feng, Feng and Ling2014), although the last account is questionable. Cessipylarum Nazarov in Afanasieva, (Reference Afanasieva1986) and Cessipylorum Nazarov and Ormiston (Reference Nazarov and Ormiston1993) were later synonymized with Kalimnasphaera following revisions by Noble and Webby (Reference Noble and Webby2009), Pouille et al. (Reference Pouille, Danelian, Ghobadi and Popov2013), and Noble et al. (Reference Noble, Aitchison, Danelian, Dumitrica, Maletz, Suzuki, Cuvelier, Caridroit and O'Dogherty2017). However, micro-CT scans of Kalimnasphaera indicate substantial differences between the skeletal architectures of Kalimnasphaera and the diagnosis provided for Cessipylorum.

Kalimnasphaera pingliangensis new species
Figures 10, 11.4

Reference Wang1993

Inanihella penrosei Wang, p. 102, pl. 1, figs. 2–5, pl. 2, figs. 1–9, pl. 3, figs. 1, 3, pl. 4, figs. 2, 3.

Reference Webby and Blom1986

Kalimnasphaera? sp. Webby and Blom, pl. 3, fig. 10, pl. 4, fig. 1.

Figure 10. Structural details highlighted using micro-CT model of Kalimnasphaera pingliangensis n. sp. (paratype, SEES/140703-55-KP2). S_P: primary spines initiating from microsphere. S_Sm: secondary spines initiating from medullary shell. S_Sc: secondary spines initiating from cortical shell. S_Py: secondary spines associated with pylome. (1) SEM image, colorized, corresponding to micro-CT images; (2) cross section showing the arrangement of three spheres; (3) cortical shell and types of spines; (4) medullary shell; (5) microsphere and three primary spines (S_P) originating from it (black sphere inserted to aid visualization); (6) pylome and the two associated spines (S_Py); (7) primary or secondary spines supported with buttresses; (8) secondary spine (S_Sc) with a simple base initiating from the cortical shell. Scale bars are (1–3) 100 μm; (4, 5) 25 μm; (6–8) 60 μm.

Holotype

Specimen no. SEES/140703-55-KP1 (Fig. 11.4) and paratypes SEES/140703-55-KP2 (digitized as Fig. 10 and Supplemental Data 7) and SEES/140703-55-KP3 in the micropaleontology collection of SEES-UQ. Known from Sandbian limestone beds in the Pingliang Formation, Guanzhuang section, Gansu Province, China.

Diagnosis

Kalimnasphaerid lacking a fenestrate outer shell with few by-spines on the limited cortical shell surface. Pylomate cortical shell is perfectly spherical. Three primary spines originate directly from the inner reticulate microsphere and penetrate the single-layered medullary shell and cortical shell. The rest of the beams originate on the surface of the medullary shell and pass through the cortical shell forming secondary spines. At least six spines, including the three primary spines, develop buttresses on the cortical shell surface. Two secondary spines with simple bases guard a rimmed pylome on cortical shell.

Occurrence

Sandbian to Katian from China (Wang, Reference Wang1993, and herein) and Australia (Webby and Blom, Reference Webby and Blom1986).

Description

Observations using micro-CT reveal K. pingliangensis is exclusively constructed of three separate spheres interconnected by beams. The cortical shell (Ø = 325 μm) is porous, with sub-circular pores of Ø ranging from 6–20 μm (Fig. 10.3). Pore frame maintains a consistent thickness, except in areas with secondary recrystallizations. Medullary shell (Ø = 120 μm) is centrally located within the cortical shell (Fig. 10.4). It is generally imperforate despite having regularly arranged elevated polygonal-shaped pore frames. Random perforations can be seen between pore frames, but it is not clear whether this is an original feature. The innermost initial skeleton (Ø = 44 μm) is constructed with thin bars coalesced to form a microsphere along with three rod-like beams merging with the medullary shell (Fig. 10.5). The position of this microsphere within the medullary shell is uncertain (it appears to be dislocated in the scanned specimen). Three beams emanating from the microsphere develop at ~120° to one another (Fig. 10.5). They traverse through the medullary shell and emerge from the cortical shell forming rod-like primary spines with massive buttresses, which extend up to 840 μm in length (Fig. 10.7). Medullary shell gives rise to three secondary spines that penetrate the cortical shell with buttresses and few other secondary spines that have no significant base on the cortical shell. One or two secondary spines with simple bases originate from cortical shell itself (Fig. 10.8). Both primary and secondary spines have no apophyses. They taper distally, but remain as rods of Ø = 30 μm for most of their length. Some may bend slightly close to the base, while the rest are straight. Two secondary spines with regular bases are located in close proximity to the pylome, having a Ø ≈ 65 μm and fringed with an elevated rim (Fig. 10.6). Several conical by-spines on the cortical shell surface extend up to 50 μm.

Etymology

Named after the Pingliang Formation in China, where the type locality is situated.

Remarks

The species possesses a strong preservation bias compared to the rest of the assemblage. The absence of a fenestrate outer shell is characteristic because the primary, secondary, or by-spines had not developed apophyses to support lateral spinules as seen in K. maculosa. In addition, the medullary shell is not double-walled, as mentioned by Noble and Webby (Reference Noble and Webby2009). However, it should be noted that Webby and Blom (Reference Webby and Blom1986) recognized a “double walled medullary shell” as two separate shells with Ø = 13 μm and 40 μm. Over 20 specimens with good preservation were observed and none provided evidence for the existence of a fenestrate shell. Because K. pingliangensis n. sp. is a predecessor of K. maculosa, it is possible that the distinctly separate spheres seen in older forms may have combined at a later stage to form the double-walled, medullary-shelled morphotypes. However, Webby and Blom (Reference Webby and Blom1986, fig. 3.10) appears similar to K. pingliangensis, justifying its tentative assignment to K. maculosa. During the first study of the Pingliang Formation for radiolarians, Wang (Reference Wang1993) reported the presence of Inanihella penrosei. However, the figures in that paper clearly illustrate specimens of K. pingliangensis. Indeed, the wide range of dimensions Wang (Reference Wang1993) measured for elements of the shell, as well as an unmentioned third sphere, which can be clearly seen in Wang (Reference Wang1993, fig. 2.7) suggests assignment to I. penrosei was inappropriate.

Since Kalimnasphaera pingliangensis, which occurs in both N. gracilis and C. bicornis biozones, appears to be facies independent and may prove to be a useful index fossil alongside with Protoceratoikiscum spp., which is regarded as an index fossil for the Sandbian in the radiolarian biozonation of Aitchison et al. (Reference Aitchison, Suzuki, Caridroit, Danelian and Noble2017b). We note that K. pingliangensis occurs mostly in deep marine facies, such as cherts, which may explain its absence in an assemblage from a shallow-water, calcareous section.

Type species

Astroentactinia ramificans Nazarov, Reference Nazarov1975 (GIN 4333/6) from Bestamak Formation, SW foothills of Chingiz Range, eastern Kazakhstan, by original designation.

Holotype

Specimen (NIGPAS-R0116) from Pingliang Formation, Gansu Province, China (Wang, Reference Wang1993, pl. 9, fig. 11).

Remarks

The specimen figured as Oriundogutta bella in Wang (Reference Wang1991), which was recovered from the Pingliang Formation, was not accompanied by any species description. Wang (Reference Wang1993) again used the same specimens from his 1991 study, adding some additional specimens, to formally introduce Oriundogutta bella with a proper species description and a designated holotype.

Only seven spines are visible. However, spine orientation suggests one other spine may be accommodated in the vacant surface towards lower-right position of the shell. The dimensions of shell elements correspond well with the holotype. The type material comes from older strata in the same section.

Holotype

Specimen (NIGPAS-R0135) from the Pingliang Formation, Gansu Province, China (Wang, Reference Wang1993, pl. 10, fig. 17).

Remarks

Poorly preserved single specimen shows slightly larger shell dimensions (shell Ø = 104 μm and spine length is ~54 μm) than that of the holotype (Ø = 80–100 μm and length of primary spines = 30–50 μm). The number of spines is not predictable, but appears to be more than eight. The specimen is thus tentatively assigned to O. ?miscella minuta.