Genus Conoglobigerina Morozova 1961
Conoglobigerina helvetojurassica (Haeusler) 1881 neotype
Figure 6; Fig.10.1 (neotype) and Fig. 10.2–9; Fig. 11.1a–e.
1881 Globigerina helvetojurassica Haeusler. p. 36, plate 2, figs. 44, 44a.
1890 Globigerina bulloides d’Orbigny var. helveto-jurassica Haeusler, 17, p. 118, plate 15, fig. 46.
1968 ‘Globigerina’ helvetojurassica Haeusler, Oesterle, p. 774–777, fig. 50 (3 specimens with 9 illustrations).
2013 Favusella hoterivica (Subbotina). Görög and Wernli, p. 286–287, fig. 5, nrs. 1–8.
Non 1986 Globuligerina oxfordiana (Grigelis), Stam, p. 110–112, plate 7, figs. 6–12, plate 8, figs. 1–3. (Note: Stam 1986 lumped his G. helvetojurassica in G. oxfordiana).
Non 1997 Haeuslerina helvetojurassica (Haeusler), Simmons et al., p. 28, 29, plate 2.6, figs. 1–8.
Description: Low to medium high trochospiral, with an H/D ratio of 0.5–1; the trochospire axis may be slightly curved, such that the chambers of the final whorl sit oblique of the chambers of the previous whorl. No preferred coiling direction observed. Last whorl flaring out and much larger than previous (2) whorls. Spherical-circular chambers (ball shaped), four in the last whorl; chambers in the last whorl not much increasing in size. Umbilicus generally open and wide, rarely narrow. Sutures depressed, mostly straight. Aperture variable in shape, low to medium high arch, umbilical to slightly extraumbilical; a looped aperture was rarely observed also. The aperture often has a thickened rim around it. A bulla is observed in some specimens. Wall pustulose and reticulate to strongly reticulate.
Type locality and stratigraphic level: Birmenstorfer Schichten, Eisengraben Section, Transversarium Zone, Middle Oxfordian, Canton Aargau, Switzerland.
Occurrence: Middle Oxfordian of Switzerland (Sample EG4 mid, Birmenstorfer Schichten) and Lower Kimmeridgian of Central Portugal (Samples 24/2P and T2/12, respectively, in the middle and upper part of the Tojeira Formation).
Discussion: Lower spired and smaller specimens of C. helvetojurassica can be mistaken for Globuligerina oxfordiana. C. helvetojurassica has a large last whorl, flaring out, ball-shaped chambers that increase little in size and a semi-reticulate to strongly reticulate wall texture. Such is not known from G. oxfordiana, G. bathoniana or from G. dagestanica.
The specimens from the lower Kimmeridgian of Les Bouchoux, France described by Görög and Wernli (2013) as Favusella hoterivica fit in the morphological variation of C. helvetojurassica and confirm the taxon ranging upwards from Oxfordian into Kimmeridgian. The Kimmeridgian occurrence of C. helvetojurassica is now also known from Portugal (Tojeira Formation).
I postulate Globuligerina oxfordiana to be ancestral to Conoglobigerina helvetojurassica. The two taxa may be morphologically confused if no detail of the wall texture is available. For the latter a good binocular or low magnitude (200x) petrographic microscope will do, but SEM visualization is a must for detail. C. grigelisi is more compact than C. helvetojurassica, with less globular and more oblong chambers in the last whorl. The last whorl strongly embraces previous whorls (almost) down to the apex, a feature not seen in C. helvetojurassica. The umbilicus in C. grigelisi is narrow and the sculpture of the wall surface texture is often (but not always) less perfectly reticulate.
Haeusler (1881) described Globigerina helvetojurassica in free specimens with calcareous test from the Birmenstorfer Schichten, Transversarium Zone, Middle Oxfordian, Canton Aargau, Switzerland. The description (translated from Latin) runs:
Test rounded, whitish, smooth, rarely a little rough, with 5–6 chambers, the last five ones but little increasing. With larger magnification finely perforate. Many specimens are broken. On good specimens the half moon shaped openings are easily visible; (our note: this clearly refers to an arch-like aperture).
Despite above text, description was inadequate, and no type locality and no type specimens were selected.
Gygi (1969) designated the Eisengraben section (ca 30 km NW of Zurich, Canton Aargau) as type section of the Birmenstorfer Schichten. In the year before, Oesterle (1968) had already selected the same section (see Figs. 3, 4 of the lithostratigraphic column) as type locality for all foraminiferal species described in 1881 by R. Haeusler from the Birmenstorfer Schichten.
Oesterle (1968) also re-described the foraminiferal assemblage in the type locality of the Birmensdorfer Schichten. In this outcrop section, he found about 250 recrystallized and badly preserved specimens of presumably ‘Globigerina’ helvetojurassica Haeusler.
Unfortunately, and probably because he did not find suitable material in the type section, Oesterle’s (1968) description of this species is based on recrystallized, silicified (? pyritized) moulds from another locality, the so-called Renggeri Tone from Liesberg, 75 km west of the Eisengraben section, SE of Basel.
‘Tests consist of 10–14 globular chambers in 2.5–3? whorls; last whorl strongly expanded; sutures straight, deeply incised; half circle like, arched aperture in umbilical to weakly extraumbilical position. Tests are 170–220 µm in diameter and 90–120 µm high’.
The excellent drawings provided by Oesterle (1968) in Fig. 6 leave no doubt as to the identity of the taxon, except for the wall structure (but see below).
Oesterle reported that his G. helvetojurassica differs from G. oxfordiana by a higher trochospiral test. These steinkern finds from Oesterle (1968), not coming from the designated type locality of G. helvetojurassica (i.e. Birmensdorfer Schichten in Eisengraben), and being higher spired, were included by Stam (1986) in Globuligerina bathoniana.
With assistance of H. Bolli and R. Gygi, Bert Stam obtained, what he thought were topotypes of Oesterle’s Globigerina helvetojurassica. The few specimens (see Fig. 8.1–7) were obtained from the same layer as Oesterle’s sample number 4 in layer 3 from ‘ca 20 cm rostbrauner Eisen-Oomikrit mit Aufarbeitungen und spärlichem Biodetritues, sehr stark limonitisiert und korrodiert’ (Figs. 3, 4). Stam (1986) described the specimens as low trochospiral, aperture semicircular to low and elongated slit, bordered with a lip and umbilical to extraumbilical in position. The author grouped the specimens together with G. oxfordiana, and applied for Nomen Oblitum status of the original Globigerina helvetojurassica Haeusler with the International Commission on Zoological Nomenclature (dd. 3 November 1985). This request was denied.
Simmons et al. (1997) used the three specimens illustrated originally by Stam (1986) of ‘G. helvetojurassica’ from layer 3 of the type Birmenstorfer Schichten to erect the new genus Haeuslerina helvetojurassica (Haeusler). The authors also re-illustrated Stam’s figured specimens (see Fig. 8.1–7). All specimens are covered in pseudomuricae, not aligned into ridges, and possess a small umbilicus and an intra-extraumbilical, low slit aperture.
It should be noted here that Haeusler specifically listed his Globigerina helvetojurassica to have a half moon shape (arched) aperture, and not a low slit. Oesterle’s specimens all have an umbilical placed arched aperture. Also, the original specimens are higher coiled and more expanding in width than reported by Stam (1986) and Simmons et al. (1997). Hence, both Stam (1986) and Simmons et al.’s (1997) concept of helvetojurassica (with an umbilical to extraumbilical slit aperture, and lower coil) diverges from the original species descriptions and illustrations.
In 2016, Gradstein re-studied the original three specimens of G. helvetojurassica from the Birmenstorfer Schichten, deposited by Oesterle (1968) in the Natural History Museum of Basel under collection nrs. C-25692, C-25693 and C-25695. Note that slide nr. C-25694 is barren. These specimens are from Oesterle’s samples 8 and 11 in the type section (Fig. 3). The specimens consist of moulds of crystallized carbonate fragments (no nannofossils observed) without the original wall. Test is a low to medium high spire; chambers spherical, globular, regularly increasing in size; last whorl with four chambers in the last whorl; aperture a low to medium high arch, umbilical to slightly a-central in position; in one specimen the aperture tends to become loop shaped.
In my view, these few specimens are different from the flat specimens with a slit aperture, illustrated by Stam (1986), and re-imagined by Simmons et al. (1997).
I am of the opinion that the original specimens of G. helvetojurassica from Oesterle–Haeusler as described and re-studied by me, do not resemble the three specimens described by Stam-Simmons.
When in Basel, Gradstein also studied many Birmenstorfer type section specimens in another set of Oesterle (1968) slides, numbered 26,092 (sample levels 6–12 in Fig. 3), 26,095 (sample numbers 19–22 of Fig. 3), 26,094 (sample number 18 of Fig. 3) and slide nr. 26,093 (sample numbers 13–17 in Fig. 3). Note that there are no specimens in the Oesterle’s collection in Basel of the sample 4, level 3 collected by Stam (1986). All of the 50+ of many more (often broken) specimens which we studied show the same test moulds of crystallized carbonate fragments. The peculiar preservation is the result of a rigorous processing technique (likely a form of acetolysis). Curiously, in the material of the Natural History Museum of Basel at least five morphotypes may be distinguished, which, despite poor preservation, can easily be assigned to the species G. aff. oxfordiana, G. aff. bathoniana, G. aff. jurassica (with an elongated, high spired and irregularly trochospiral test), G. aff. balakhmatovae, G. aff. tojeiraensis(with slightly elongated last chamber) and Conoglobigerina aff. grigelisi. The affinis assignment is meant as a precaution when dealing with specimens without original wall structure. Scanning electron microscope illustrations are in Fig. 9.
From this direct study of original, but badly processed material, it is clearly not possible to understand the test morphology of Globigerina helvetojurassica Haeusler, sensu Oesterle (1968). This, plus the apertural morphological divergence mentioned above, place doubt on the assignment of the three Stam (1986) specimens of G. helvetojurassica to the new genus Haeuslerina helvetojurassica by Simmons et al. (1979). An unfortunate incident is that at this time of writing (October 2016) it is not known where Stam’s original specimens are. The specimens were loaned in 1996 from the Geological Survey of Canada to Simmons et al. (1997).
It is now clear that the species G. helvetojurassica sensu Haeusler and Oesterle cannot be defined from the studies by Stam (1986) and Simmons et al. (1997). And designing a new monotypic genus (Haeuslerina helvetojurassica) on three (?) lost specimens of a misunderstood species, does not appear to be viable.
At this stage of investigation, it was useful for taxonomy to discover if level 3 of the Birmenstorfer Schichten type section indeed would yield specimens as described by Stam (1986). Note, that such specimens are not known in the type collections of the Birmenstorfer Schichten in the Natural History Museum of Basel.
With the regional expertise and excellent assistance of the staff of the Natural History Museum in Basel (W. Etter, M. Knappertsbusch and C. Meyer) and students, two sections of the Birmenstorfer Schichten were re-sampled, including the Eisengraben type section (Figs. 3, 4). Our samples 4 mid, 4 top and 12, corresponding to Oesterle’s sample notation of the latter section yielded specimens of planktonic foraminifera. Sample 4 top has many agglutinated taxa, but hardly any planktonic specimens. Sample 4 mid, at the level of Stam’s sample with ‘helvetojurassica’ has best preserved specimens, and also includes well-preserved bentics belonging in Bigenerina, Textularia, Ophthalmidium, Ammodiscus, Glomospira, Trochammina, Haplophragmoides, Dentalina, Nodosaria, Lenticulina plus someindeterminate taxa. Micro-gastropods also occur. Small limonitic concretions are common; small glauconite lumps also occur, testifying to a likely neritic mode of deposition. There are no epistominid taxa.
The many and well-preserved planktonic specimens from sample 4 mid can be assigned to several taxa. A small number of 125–150 µm sized specimens have a low to medium high spired test with four globular chambers in the last whorl, a low to medium arched or looped aperture, with rim. The second chamber of the last whorl sticks up, as observed often in G. oxfordiana. Wall surface structure is pustulose. The specimens do not resemble in any way G. helvetojurassica sensu Stam (1986), and belong in G. oxfordiana. Other taxa observed include Globuligerina bathoniana and isolated, small (65 µm fraction) and poorly preserved specimens indeed resembling Haeuslerina helvetojurassica sensu Simmons et al. (1997). Low numbers of these tiny specimens, and poor preservation prevent proper description.
The importance of this find is in the other, more common and much better preserved specimens. Specimen vary in size from ~100 to ~180 µm, are well preserved with a medium high spire, globular chambers, deeply incised sutures and medium high arched aperture with rim. The last whorl is large relatively to the previous whorls, with the four chambers in this whorl little increasing in size. The last whorl does not overlap the previous whorls as much as in Conoglobigerina grigelisi. The wall surface structure is reticulate to strongly reticulate. The test morphology of the specimens bears a remarkable similarity to the drawings by Oesterle (1968) of G. helvetojurassica (compare specimens in Fig. 6 with specimens in Fig. 10) and concur with the original description by Haeusler (1881).
With this new find, a neotype is proposed for Globigerina helvetojurassica Haeusler under the name Conoglobigerina helvetojurassica (Haeusler). The neotype is the specimen on Fig. 10.1 with typical specimens from the same locality on Fig. 10.2, 3 and 4. From Montejunto, Portugal specimens of this taxon are illustrated on Fig. 10. 5 through 9. The new findings confirm that this species can again be properly defined and included as a valid taxon among the Jurassic planktonic foraminifera.
Benthic life cycle stage?
Figure 11.1a–e shows SEM digital images of an unusual Swiss specimen assigned to Conoglobigerina helvetojurassica (Haeusler). Only one specimen was obtained (sofar) after picking five trays with washed residue, but its features are clear enough. The overall chamber shape, wall structure and wall texture indicate it most likely belongs in this taxon.
The planoconvex and involute test is relatively large (150–200 µm in diameter) and has four chambers in the last whorl, with chambers slightly increasing in size. Aperture is not preserved. The wall is microperforate and wall textures reticulate.
Normally, C. helvetojurassica has a medium high trochospiral test, but as seen on Fig. 11.1c the spiral side is concave and involute and not trochoid and evolute. Concave spiral sides maybe observed with sessile foraminifera that are attached to a hard surface. Such attachment surfaces maybe somewhat irregular in shape and the foraminiferal test may accommodate such a surface; hence a concave test shape might occur if the attachment surface is convex. The actual surface attachment spots on the specimen of C. helvetojurassica are clearly shown on Fig. 11.1c as darker coloured, rather smooth surfaces on chambers 1 and 3 of the last whorl.
A peculiarity is the small test with five (?) globular chambers in a flat coil that under higher magnification appears to be microperforate and pustulose or semi-reticulate. It is attached to the larger specimen, but appears to be a separate individual. More specimens are required to assemble a thorough description and interpretation. At this stage the large specimen is considered a possible benthic, attached life cycle individual of the nominate taxon.
Jurassic planktonic foraminifer sp.
Figure 11.2 and 3
At the sample level 4 mid with Conoglobigerina helvetojurassica in the Eisengraben Section of the Birmenstorfer Schichten, four small (less than 125 µm) specimens were found, two of which may be assigned to Globuligerina bathoniana. Two other ones appear to be a new taxon, not described earlier.
The test is triserial or slightly trochoid coiled, with three whorls; test chambers regularly increase in size. Last chamber markedly sticking up. Aperture not preserved. Test wall is microperforate and reticulate and shows many low and longitudinal ribs, crossing chamber sutures.
Until more and better preserved specimens are located, it is refrained from formally describing this taxon. Conoglobigerina pupaWernli and Görög 2007 (their plate 4, figs. 1 and 2) bears resemblance, including what looks like striation on these specimens from the Middle Jurassic of France.
Genus Globuligerina Bignot and Guyader 1971.
Globuligerina tojeiraensis sp. nov. Gradstein
Holotype in Fig.12.1. Paratypes in Fig.12.2–10. Types are from Sample 24/2P taken in 1978 from the middle Tojeira Formation, Montejunto, Portugal, Platyna through Platynota Zones, Early Kimmeridgian. Sample 24/2P was positioned slightly above the thin limestone beds in Fig. 2.
Description: Relatively low to medium high trochospiral, with an H/D ratio of 0.3–05, rarely larger. Test consists of 2–3 whorls with a tiny initial chamber (where visible). No preferred coiling direction observed. Last whorl with four chambers, which strongly increase in width, flaring out. Chambers are rounded with deeply incised sutures; chambers in the last whorl often radially elongate and higher than broad; last chamber often pointing slightly left or right in the equatorial plane. The test has a sunk-in umbilical region; umbilicus small to large (wide open). G. tojeiraensis has this peculiar knack (depressed umbilicus) with surrounding chambers often sticking up two by two. The chambers 2 and 4 of the last whorl stick more up than chambers 1 and 3.
Aperture a low to rarely high arch; it may be slightly asymmetrical in shape, as shown on Fig. 12.5a; aperture generally umbilical in position, rarely umbilical—extraumbilical. A small bulla occurs rarely; it obscures the aperture of the final chamber. Wall pustulose; pustules may fuse to form broken ridges.
Differential diagnosis: G. tojeiraensis differs from G. oxfordiana in its elongated (stretched) chambers in the last whorl, often oblique last chamber (pointing left or right), and often wide open umbilicus. The wall sculpture is densely pustulose, with pustules forming broken ridges; a trend not normally seen in G. oxfordiana. G. tojeiraensis is generally higher spired than G. balakhmatovae and G. oxfordiana and lower spired than G. bathoniana, none of which have elongated chambers, or a wide umbilicus.
Range and occurrence: The type level is the Tojeira Formation, Montejunto Formation, central Portugal of Early Kimmeridgian age (Planula-Platynota zones). The species is common in the Portugese outcrops.
A number of small, compact specimens with limited umbilical opening, but typical oblique last chamber occur in swc 5000′, Bittern M-62 well, Grand Banks. The sample is of Late Callovian to Early Oxfordian age (Gradstein et al., in prep.).
The taxon probably also occurs in the Birmenstorfer Schichten (Oxfordian), Canton Aargau, Switzerland.
Non-reticulate specimens of Conoglobigerina caucasica Gorbachik and Poroshina (1997) from the early Berriasian of Azerbijan, shown by Simmons et al. (1997) on their plate 2.6 may belong in Globuligerina tojeiraensis. Possibly, this species extends from Kimmeridgian into Berriasian. More discussion on this is in Gradstein et al. (in prep).
Phylogeny: In Bittern M-62 well, compact specimens with a ‘sideways leaning’ last chamber assigned to G. tojeiraensis have the second chamber of the last whorl typically ‘sticking up’, as in G. oxfordiana. In the Portugese material, where the taxon is common, morphological transitions occur to G. oxfordiana. Hence, this indicates that the latter is a possible ancestor.
Genus Conoglobigerina Morozova 1961
Conoglobigerina grigelisi sp. nov.
Conoglobigerina ?avariformis Kasimova, Görög & Wernli 2013, p.285, fig. 4, nrs. 8–13.
Holotype in Fig. 13.1. Paratypes in Fig.13.2–10. Types are from sample 24/2P taken in 1978 from the middle Tojeira Formation, Montejunto, Portugal; Platyna through Platynota Zones, Early Kimmeridgian. Sample 24/2P was positioned slightly above the thin limestone bed in Fig. 2.
Description: Low to medium high conical test with a compact spire and 3.5–4 chambers in the last whorl. H/D ratio 0.5–1, rarely over 1. No preferred coiling direction observed. The chambers of the last whorl are large and have deeply incised sutures. Last whorl strongly embraces previous (? 2) whorls such that the earlier part of the test maybe hardly visible. Apex generally blunt, rarely pointed. Umbilical area depressed. Aperture generally a more or less symmetrical arch with lip, rarely comma-shaped. Specimens may have a small bulla over the umbilicus with one or two, low-arch apertures; it may resemble the bulla structure of Cenozoic Catapsydrax taxa. Wall microperforate, strongly pustulose; pustules form low and broken ridges that create an imperfectly reticulate pattern over the surface of the chambers.
Conoglobigerina grigelisi Gradstein sp. nov. is named after Algimantas Grigelis for his early study of Jurassic planktonic foraminifera.
Differential diagnosis: Conoglobigerina grigelisi sp. nov. differs from G. bathoniana in its more compact test, strongly embracing chambers in the last whorl, often wider last whorl and wider umbilicus, and by its densely pustulose, reticulate wall sculpture. The pustules form broken ridges that arrange in an imperfect, low reticulate pattern over the whole test. C. helvetojurassica has more spherical, globular chambers which do not so strongly overlap previous whorls as in C. grigelisi.
The specimens of C. grigelisi in shape somewhat resemble Globuligerina avariformis (Kasimova, 1984) from the Bajocian of Azerbaijan. This taxon is poorly documented, but the original description under the genus name Conoglobigerina by Kasimova and Aliyeva (1984) mentions a smooth test and low arch aperture. The original drawings of the holotype show that the last whorl much less embraces the test than in C. grigelisi sp. nov. Gorog and Wernli (2002) report common C. aff. avariformis from the middle and late Bathonian of Hungary.
The SEM illustration on Fig. 8.8–10 of a specimen of G. avariformis (Kasimova) from Simmons et al. (1997), donated by G. K. Kasimova to the Museum of Natural History, London, UK shows the rather smooth wall and compact test. The sutures are less incised than in our specimens of C. grigelisi sp. nov. Another key difference is that the Bajocian age specimens from Azerbaijan have a wall with low pustules and ridges, instead of a dense muricate and rather reticulate wall sculpture. In C. grigelisi the last whorl also is more embracing the older part of the test.
Görög and Wernli (2013) described a morphotype from the Kimmeridgian of SE France under the name C.? avariformis, using acetolysis, that strongly resembles C. grigelisi sp. nov.
Range: Common in the Tojeira Formation, Lower Kimmeridgian of Central Portugal, and observed with few, small specimens in slightly older strata on the Grand Banks. Likely occurs also in the Kimmeridgian of SE France.
Phylogeny: The more embracing test and more advanced wall texture of C. grigelisi sp. nov. compared to G. avariformis (Kasimova) may indicate an evolutionary trend from the latter to the former taxon in Late Jurassic time. A problem is the lack of record of the latter in Callovian through Oxfordian strata.
Globuligerina oxfordiana (Grigelis) subspecies calloviensis ssp. nov. Gradstein
1980 Globuligerina calloviensis Kuznetsova. In Kuznetsova and Uspenskaya 1980, p. 750, plate 2, figs. 1–4.
1986 Globuligerina calloviensis Kuznetsova. In Gorbachik 1986, plate 5, fig. 3; plate 6, fig. 1–2.
Description: Based on more than 200 specimens in Lower Callovian strata from the Meganom Peninsula, Eastern Crimea, K. Kuznetsova in 1980 described Globuligerina calloviensis. The low trochospiral test of two whorls has a low convex spiral side and a slightly concave umbilical side, with a fairly wide umbilicus. The second whorl is much wider than the first one. On the relatively poor illustrations the aperture is not well visible, but maybe a low arch; the wall appears smooth. The illustrations are in contrast to the description that describes a tuberous and cellular wall structure. Variability is in the flattening of the test, with more convex specimens being rare.
Stam (1986) included G. calloviensis in G. oxfordiana. Simmons et al. (1997) also argued that G. calloviensis is morphologically very close to G. oxfordiana and might be considered a subspecies of the latter. Despite limited data on definition and restricted distribution, this species of Jurassic planktonic foraminifera was retained by Simmons et al. (1997), who illustrated metatypes (see Fig. 8.1–6). These specimens clearly show the comma-shaped aperture and overall test shape like G. oxfordiana. The remarkable feature is the lack of ridges (pseudomuricae) on the test surface, which appears almost smooth. This is in contrast to the original description by Kuznetsova. The tests are not internal moulds. We conclude that there is wide variation in sculpturing and preservation of the type specimens, which should be investigated.
We assign the type, which has not been reliably recorded outside the Callovian of the Crimea and Ukraine, subspecies status, as suggested by Simmons et al. (1997). Stam (1986) on his plate 14, figs. 8–14, shows specimens of G. oxfordiana from the Tojeira Formation, Montejunto in Portugal that well resemble the type illustration by Kuznetsova and the metatypes of G. calloviensis illustrated by Simmons et al. (1997).
The only difference is the more rugulose wall of the Portugese specimens that are also younger in age than the types.
I take the opportunity to mention the possible similar preservation of some Callovian specimens of G. bathoniana figured in Stam (1986) from Algarve, Southern Portugal. Although some of these Algarve specimens appear to be internal moulds, some others appear to be thin-shelled, as if Callovian Jurassic planktonic foraminifera underwent an unusual change in wall structure.
Genus Globuligerina Bignot and Guyader 1971
‘Globuligerina’ stellapolaris Grigelis et al. 1978
Figure 7; Fig.14.1–7; Fig. 15.2, 4, 6 and 8.
Globuligerina stellapolaris Grigelis et al. 1978 (in 1977 in same journal in Russian). p. 926–927.
Compactogenerina stellapolaris (Grigelis).Simmons et al. 1997, p. 29, plate 2.7, figs. 1–7.
Original description: The test is small, trochoid and round. Dorsal side is low trochospiral, and the ventral side involute. The spire consists of two whorls, with three chambers in the first whorl and four in the second and last whorl. The chambers are round and adjoin each other closely. Sutures are linear and slightly incised. The aperture is arch (arcuate) shaped. The test wall is calcareous, thin and with large pores. The H/D ratio of the holotype is 0.72 and over 200 µm large.
The taxon differs from Globuligerina oxfordiana in the round (not oval) shape of the test, greater size, and its more closely packed chambers.
Twenty or more specimens were found in the type area, some fairly well-preserved. The types are stored in the Lithuanian Institute of Geological Exploration, Vilnius, Lithuania.
The types of ‘Globuligerina’ stellapolaris are from very thin Upper Jurassic strata outcropping along the banks of the Pizma and Ishma Rivers in the Pechora Basin. A description of the outcrops is in the section on Material. Note that this occurrence is unusual in that other latest Jurassic planktonic foraminifera occur much further south (Hungary).
The well-placed taxonomic remarks by Simmons et al. (1997) are: ‘The holotype figure by Grigelis et al. (1978) is a specimen with a very compact test, in which the sutures are only slightly depressed and the equatorial periphery is not lobulate. This morphology agrees with that of two metatypes illustrated here (plate 2.7, figs. 1–3, 7). The sutures of another topotypic specimen also illustrated on plate 2.7, figs. 4–6, however, are much more depressed and the equatorial periphery is more lobulated. If the specimens figured here are indeed all conspecific, then they give a view of the range of variation which occurred in the species, but not enough specimens are available to us to be sure. The aperture possesses a narrow lip which partly covers the umbilicus (this lip appears to be broken away on plate 2.7, fig. 6)’.
Sofar the wording in the original descriptions by Grigelis et al. (1978) and twenty years later by Simmons et al. (1997). The metatypes are re-illustrated here in Fig. 14.1–7.
My first comment is that if peripheral test shape is a generic feature than G. bathoniana surely should be a different genus from G. jurassica and from G. oxfordiana. Both metatypes grouped by Grigelis under ‘Globuligerina’stellapolaris and illustrated here also might be split in two different genera. Hence, the genus name Compactogenerina assigned by Simmons et al. (1997) to the ‘G’. stellapolaris specimens of Grigelis et al. (1978) is not followed here. Generic splitting obscures detailed taxonomy, paleobiogeography and evolutionary trends.
A second comment is that the original description specifically refers to large pores. A photograph of a strongly encrusted specimen of ‘G’. stellapolaris, kindly shown by Grigelis to the author in 2016 in Vilnius, shows long vertical pores over 9 µm in diameter. Planktonic species with large pores are only known from Middle Cretaceous and younger strata, hence this give hint of an unusual situation (see below).
A third comment is that it is curious that (after 40 years) no reliable record exists of the species outside the type locality, which also is unusually far north (~67° N), well outside the common distribution realm of Jurassic planktonic foraminifera. It is possible to pick morphotypes somewhat resembling ‘G’. stellapolaris in the Kimmeridgian Tojeira Formation at Montejunto, Portugal. But these specimens do not have large pores or the type of reticulate wall surface, as ‘G’. stellapolaris is described with. Such Montejunto specimens somewhat resembling ‘G’. stellapolaris are aberrant, dwarfed and stunted specimens of C. helvetojurassica or of C. grigelisi. These specimens mostly have a bulla, with one or two apertures that obscures the primary aperture. We consider that such specimens belong in the natural, albeit gerontic variation of the two Conoglobigerina taxa.
Similarly, Görög and Wernli (2013, fig. 4.14) found a single specimen of Compactogenerina stellapolaris in Lower Kimmeridgian strata of the Jura Mountains, France. Unfortunately, Kimmeridgian sample processing was with acid, destroying wall texture. The specimen has a bulla hiding the aperture and what looks like resorbed wall distorting the shape of the last two chambers. The wall structure appears different from that shown by the metatypes of C. stellapolaris in Simmons et al. (1997). It may be an aberrant specimen of another taxon.
This brings me to the important issue that the types of ‘G’. stellapolaris show a partly recrystallized and strongly reticulate wall surface pattern. In June 2016, the author and L. Kopaevich (Moscow) visited A. Grigelis in Vilnius for the purpose of studying both G. oxfordiana and the types of ‘G’. stellapolaris. The holotype of the latter looks very compact, with a coarse reticulate wall, and might readily be confused with Late Cenozoic Neogloboquadrina pachyderma (Ehrenberg), if no Jurassic ammonite data were supporting its sampling.
Two samples without ammonite control of the same (and very thin) Volgian levels in the type area of Pizhma were kindly loaned by Grigelis to the author and studied in detail in Oslo, Norway. It turned out that the benthic foraminifera assemblage in these two samples (15/207 and 15/211) contains common specimens of what appear to be Reticulophragmium sp. (of a type well known from the Late Cenozoic of the central North Sea). Other specimens may be referred to Budashevaella multicamerata Voloshinova, well known from Cenozoic strata. There also is an abundance of a smooth, rather sharp conical and pointed Epistomina and rare foraminiferal genera not readily known from Jurassic strata. The Epistomina genus could be Jurassic, but could also be (much) younger; it does not resemble Jurassic E. praetatariensis or E. ulighi reported from the Volgian of Russia. Six specimens of planktonic foraminifera are also present in the slides. One specimen might be a heavily calcified Orbulina universa and the others look mostly like Neogloboquadrina pachyderma.
As a final comment, Fig.15.2, 4, 6 and 8 feature the types of ‘Globuligerina’ stellapolaris (Grigelis) in juxtaposition with Neogloboquadrina pachyderma (Ehrenberg) on Fig. 15.1, 3, 5 and 7. The latter is from the Recent in oceanic environments. The morphological resemblance is remarkable and cannot be mistaken. Although this type of comparison is not a thorough scientific exercise, it further highlights that ‘G’. stellapolaris and its original deposits and fossil content need detailed study. A. Grigelis communicated to Gradstein in December 2016 that he is looking into the geology of the original location of the taxon. Nannofossil study of relevant samples might also be useful.