Remarks.—The order Albaillellaria was introduced by Deflandre (1953). Holdsworth (1969b) 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. (1992). 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, 1963; Holdsworth, 1969a, b; Won, 1983; Cheng, 1986; Renz, 1988; Aitchison, 1993). 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. (2001) 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 (1963) introduced the basic nomenclature to describe the skeletal elements of ceratoikiscids, which was elaborated on later by several authors (Holdsworth, 1969b; Renz, 1988; Noble and Lenz, 2007) (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. (1990) 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, 2001, 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.

Type species.—Etymalbaillella yennienii Li, 1995 (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 (1995).

Remarks.—Etymalbaillella was first assigned to the Albaillellidae by Li (1995). Constituent species include E. renzii, E. toriterminalis, and E. yennienii that were first reported from Baijingsi, Qilian Mountains, China (Li, 1995). Etymalbaillella was later grouped with Proventocitum and reassigned under the Proventocitiidae (Aitchison, 1998). Noble and Webby (2009) 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. (2017). Known occurrences are significant because they come from deep marine (Li, 1995) and shallow marine (Noble and Webby, 2009) 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 (2009) on the lack of two lateral rods mentioned by Li (1995) and the absence of albaillellid symmetry. In his discussion of the genus, Li (1995, 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, 1969a, 1971; Won, 1983; Cheng, 1986; Renz, 1988; Aitchison, 1993), 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 (1986) 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, 1986), while ceratokiscids made their entrance by the Middle Ordovician (Danelian and Floyd, 2001). 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.

1995 Etymalbaillella toriterminalis Li, p. 338, pl. 2, figs. 12, 16.

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 (1995).

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 (1969b). 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.

1995 Etymalbaillella renzii Li, p. 338, pl. 1, figs. 1, 3, 5.

Holotype.—Neotype specimen no. SEES/140703-49-ER1 (Fig. 11.10) 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. Downward-facing pair of wings extends from the upper section of the intersector and a-bar. Emended from Li (1995).

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., 2010 (pl. 1, fig. 11) from Pingliang Formation in the Guanzhuang section of the Gansu Province, China by original designation.

1991 Ceratoikiscum sp. 1; Wang, p. 249, pl. 1, figs. 6, 7.

2010 Gansuceratoikiscum guanzhuangensis Wang et al., p. 475, pl. 1, figs. 1–30.

Holotype.—Specimen in Wang et al. (2010, 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., 2010).

Remarks.—Specimens recovered are most likely to be fragments of G. guanzhuangensis. Proholoeciscus foremanii reported from Qilian Mountains, China (Li, 1995), which is now regarded as a nomina dubia (Noble et al., 2017), may also be a fragment of G. guanzhuangensis because it appears similar to the specimen in Figure 12.3.

Type species.—Bissylentactinia rudicula Nazarov, 1975 (GIN. No. 4046-19) from the Egindinskaya series, Southern Urals, Northern Mugodzhars, Aitpaika River by original designation.

1980 Bissylentactinia bifida Nazarov in Nazarov and Popov, p. 64, pl. XV, fig. 2.

Holotype.—Specimen (GIN 4333/22) from the Middle Ordovician, Bestamaksk Formation, SW foothills of Chingiz Range, eastern Kazakhstan (Nazarov and Popov, 1980, 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 (1980) 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 (1980). The long stratigraphic gap existing between Darriwilian (Nazarov and Popov, 1980) and Frasnian (Nazarov, 1975) occurrences can now be reconciled with the intervening occurrence in the Sandbian reported herein.

Type species.—Haplentactinia rhinophyusa Foreman, 1963 (USNM 640392) from the Norwalk 1 calcareous concretions of the Upper Devonian Huron Member of the Ohio Shale by original designation.

1980 Haplentactinia sp. Nazarov in Nazarov and Popov, p. 55, pl. XVII, fig. 4.

1983 Haplentactinia baltica Nazarov in Nazarov and Nolvak, p. 5, pl. II, figs. 2–4.

Holotype.—Specimen (GIT 182-4), former no. GIN R2/5408, from the Upper Ordovician, Saunja Formation in Estonia (Nazarov and Nolvak, 1983, 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, 2011) 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 (1983) 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, 1980; Aitchison et al., 2017a). 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, 1986, pl. 4, figs. 1–4).

1986 Palaeoephippium radices Goodbody, p. 144, pl. 4, figs. 9–12.

1994 Palaeoephippium radices; Li, p. 266, pl. 2, fig. 6.

1995 Palaeoephippium radices; Amon et al., p. 6, text fig. 7.

2004 Palaeoephippium radices; MacDonald, p. 271, figs 5.1–5.4, 8.1–8.4.

Holotype.—Specimen (UA 7166) from the Cape Phillips Formation, Cornwallis Island, N.W.T, Canada (Goodbody, 1986, 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 (1995) 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 (1986, 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.

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, 1975; Nazarov et al., 1975; Nazarov and Popov, 1980; Wang, 1993; 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, 1975), Protopylentonema aperta (Nazarov et al., 1975), Protopylentonema rimata, (Nazarov and Popov, 1980), 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, 1975; Nazarov and Popov, 1980). These features accord with the micro-CT model created for P. ordosensis; the type species of the new genus. Nazarov and Ormiston (1993) reassigned these species (P. aperta, P. rimata, and P. insueta) to the genus Cessipylorum. Subsequently, Noble and Webby (2009) 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 (1975) and Nazarov and Popov (1980) are best placed within the new genus Protopylentonema.

1993 Inanihella penrosei Wang, pl. 3, fig. 1.

1993 Cessipylorum cf. aperta Wang, pl. 4, figs. 7, 8.

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, 1993, 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, 1999) 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, 1999). 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.

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, 1980) instead of the micro-bar. Nazarov et al. (1975) 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, 1993 (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.

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, 2020 (see Perera et al., 2020). All the spherical Haplotaeniatum species encountered from the Darriwilian Shundy Formation (Pouille et al., 2014) are larger in outer diameter compared to H. implexa. However, it closely resembles the disorderly interwoven mesh of Haplotaeniatum sp. B (ouille et al., 2014) 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., 2014) from H. implexa, although the spongy meshwork of both appears similar. The shell dimensions of Haplotaeniatum sp. A (Yi et al., 2018) 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, 1993). However, subsequent revisions to the genus by Won et al. (2002) 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., 2017; Noble et al., 2017). 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, 1995; Danelian and Popov, 2003; Suzuki, 2006; Maletz, 2011; Trubovitz and Stigall, 2018; Kachovich and Aitchison, 2020). 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, 1984; Nazarov, 1988; Noble et al., 2017). All these diagnostic features appear to be more compatible with Silurian morphotypes than those from the Ordovician (Nazarov and Ormiston, 1984, 1993; Siveter et al., 2007). However, several authors have assigned a few Ordovician species under Inanihella despite poor preservation that hinders precise identification. Inanihella (?) akzhala (Danelian and Popov, 2003) and I. bakanasensis Danelian and Popov, 2003 (reported by Danelian and Popov, 2003, and Maletz et al., 2009) do not show any trace of an inner structure within the inner sphere. Inanihella penrosei (Ruedemann and Wilson, 1936) described by Wang (1993) 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. (2013) 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 (2008) suggested the possibility of resorbing materials from inner spheres to form outer spheres during ontogeny. Meanwhile, Inanibigutta (Nazarov, 1988) only recognizes two-sphered inaniguttids, with only six primary spines. Unlike Inanigutta, the number of spines on Inanibigutta is fixed (Noble et al., 2017). 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 (2008) 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 (2008, 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 (1975) from Arenigian strata of the Ushkyzyl Formation (Zhylkaidarov, 1999) 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.

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, 1980) 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 (1993) 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.

Genus Inanibigutta Nazarov and Ormiston in Nazarov, 1988

Type species.—Entactinosphaera aksakensis Nazarov, 1975 (GIN 4333/1) from the Bestamak Formation, SW foothills of Chingiz Range, eastern Kazakhstan by original designation.

1991 Inanibigutta pinglianensis Wang, p. 249, pl. 1, figs. 11, 12.

1993 Inanibigutta pinglianensis; Wang, p. 100, pl. 5, figs. 1–8, pl. 6, figs. 1, 4.

2000 Inanibigutta pingliangensis [sic]; Song et al., p. 67, pl. 1, fig. 2.

Holotype.—Specimen (NIGPAS-R0066) from Pingliang Formation, Gansu Province, China (Wang, 1993, pl. 5, fig. 2).

Remarks.—Specimens figured as Inanibigutta pingliangensis in Wang (1991), which were recovered from the Pingliang Formation, were illustrated and named but not accompanied by a species description. Wang (1993) 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 (2003) 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 (2020) 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., 1985; Wu et al., 2014; Yang et al., 2020) indicate that the Zhaolaoyu Formation in Shaanxi Province, from which I. pinglianensis was reported for a second time (Song et al., 2000), is Late Ordovician, likely Sandbian age. Therefore, I. pinglianensis can be regarded as a good Sandbian marker taxon, especially in shallow water facies.

1976 Entactinosphaera verrucula Nazarov and Popov, p. 408, fig. 1d.

1980 Entactinosphaera verrucula; Nazarov and Popov, p. 38, pl. 3, fig. 6, pl. 11, fig. 6, text-fig. 17.

1988 Inanibigutta verrucula; Nazarov, fig. 31.

1993 Inanibigutta verrucula; Wang, p. 100, pl. 6, figs. 2, 3, 5–8.

1995 Inanibigutta verrucula; Li, p. 343, pl. 3, fig. 9.

1998 Inanibigutta verrucula; Danelian and Clarkson, p. 135, fig. 2g.

1999 Inanibigutta sp. cf. I. verrucula; Danelian, p. 630, fig. 4H.

2000 Inanibigutta aff. vurracula [sic]; Song et al., p. 67, pl. 1, fig. 6.

2001 Inanibigutta (?) sp. O Danelian and Floyd, p. 493, fig. 4b.

2020 Inanibigutta sp. cf. I. verrucula; Perera et al., p. 2039, pl. 1, fig. h.

Holotype.—Specimen (GIN 4333/18) from the Middle Ordovician, Bestamak Formation, SW foothills of Chingiz Range, eastern Kazakhstan (Nazarov and Popov, 1976, 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, 1976). Most spines on the observed specimens are broken at mid-length. Wang (1993) and Danelian and Clarkson (1998) reported Ø = 180–260 µm and 131 µm for outer sphere Ø, for which Nazarov and Popov (1976) 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, 1975 (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 (1988).

Remarks.—Inanigutta was established to include species with a single shell, demonstrating six-spine geometry (Nazarov and Ormiston, 1984). However, the diagnosis was emended to include taxa with four to five spines by Nazarov and Popov (1980) 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.

1975 Entactinia complanata Nazarov, p. 56, pl. XV, figs. 11, 12, pl. XX, figs 7, 8.

1980 Entactinia complanata; Nazarov and Popov, p. 29, pl. 1, figs. 2, 5, pl. 7, figs. 3, 4, pl. 11, figs. 3, 4, text-fig. 10.

1984 Inanigutta complanata; Nazarov and Ormiston, pl. IV, fig. 1.

?1992 Inanigutta cf. I. complanata Goto et al., p. 159, pl. 9, figs. 1–3.

1993 Inanigutta complanata; Wang, p. 99, pl. 10, figs. 1, 2.

2001 ?Inanigutta complanata Danelian and Floyd, p. 493, fig. 4a.

2009 Inanigutta complanata; Noble and Webby, pl. 5, figs. 10, 11, pl. 6, fig. 14.

?2020 Inanigutta sp. cf. I. complanata; Perera et al., p. 2040, pl. 1, fig. i.

Holotype.—Specimen (GIN 4333/29) from the Middle Ordovician, Bestamak Formation, SW foothills of Chingiz Range, eastern Kazakhstan (Nazarov, 1975, pl. XX, fig. 8).

Remarks.—Shell dimensions given in Nazarov and Popov (1980) are clearer than those in Nazarov (1975). With the exception of Wang (1993), no subsequent reports correspond exactly with original descriptions (outer shell; Ø = 190 µm and 175 µm, respectively, in Danelian and Floyd, 2001, and Noble and Webby, 2009). The dimensions given in Nazarov and Popov (1980) 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 (1980). The structure of the initial skeleton from which the spines radiate is obscure.

1993 Inanigutta gansuensis Wang, p. 99, pl. 7, figs. 1–8, pl. 8, figs. 1–11.

2013 Inanigutta gansuensis; Pouille et al., p. 1154, fig. 6.6.

2020 Inanigutta gansuensis; Perera et al., p. 2040, pl. 1, fig. d.

Holotype.—Specimen (NIGPAS-R0087) from the Middle Ordovician, Pingliang Formation, Gansu Province, China (Wang, 1993, 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 (1993) 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.

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 (1993) 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., 2013; Perera et al., 2020). Both studies mention broken spines and do not report any six-spined specimens.

Type species.—Kalimnasphaera maculosa Webby and Blom, 1986 (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, 1986.

Remarks.—Dunham and Murphy (1976) first reported Kalimnasphaera as ‘sphaeroids’ from Upper Ordovician calcareous concretions in Nevada. Material from that locality was revisited by Renz (1990) following a second encounter of the same genus from Upper Ordovician Australian limestones where it was formalized as Kalimnasphaera (Webby and Blom, 1986). Kalimnasphaera has been reported several times from Australia (Goto et al., 1992; Umeda et al., 1992; Noble and Webby; 2009), Kazakhastan (Pouille et al., 2013), and China (Cao et al., 2014), although the last account is questionable. Cessipylarum Nazarov in Afanasieva, (1986) and Cessipylorum Nazarov and Ormiston (1993) were later synonymized with Kalimnasphaera following revisions by Noble and Webby (2009), Pouille et al. (2013), and Noble et al. (2017). However, micro-CT scans of Kalimnasphaera indicate substantial differences between the skeletal architectures of Kalimnasphaera and the diagnosis provided for Cessipylorum.

1993 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.

1986 Kalimnasphaera? sp. Webby and Blom, pl. 3, fig. 10, pl. 4, fig. 1.

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, 1993, and herein) and Australia (Webby and Blom, 1986).

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 (2009). However, it should be noted that Webby and Blom (1986) 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 (1986, 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 (1993) 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 (1993) measured for elements of the shell, as well as an unmentioned third sphere, which can be clearly seen in Wang (1993, 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. (2017b). 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, 1975 (GIN 4333/6) from Bestamak Formation, SW foothills of Chingiz Range, eastern Kazakhstan, by original designation.

1991 Oriundogutta bella Wang, p. 249, pl. 1, fig. 14.

1993 Oriundogutta bella Wang, p. 101, pl. 9, figs. 1–13.

1999 ?Oriundogutta bella; Danelian, p. 632, pl. 5, fig. C.

Holotype.—Specimen (NIGPAS-R0116) from Pingliang Formation, Gansu Province, China (Wang, 1993, pl. 9, fig. 11).

Remarks.—The specimen figured as Oriundogutta bella in Wang (1991), which was recovered from the Pingliang Formation, was not accompanied by any species description. Wang (1993) 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.

1993 Oriundogutta miscella minuta Wang, p. 101, pl. 10, figs. 16, 17.

Holotype.—Specimen (NIGPAS-R0135) from the Pingliang Formation, Gansu Province, China (Wang, 1993, 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.