Tectonic setting of the Tetagouche Group in northern New Brunswick: implications for plate tectonic models of the northern Appalachians

1987 ◽  
Vol 24 (7) ◽  
pp. 1329-1351 ◽  
Author(s):  
C. R. van Staal
Keyword(s):  
New Brunswick ◽  
Large Scale ◽  
Tectonic Setting ◽  
Trace Element Content ◽  
Structural Data ◽  
Sensu Stricto ◽  
Group A ◽  
Geochemical Analyses ◽  
Group B ◽  
Back Arc

A regional compilation and reinterpretation of geochemical analyses of mafic igneous rocks from the Ordovician Tetagouche Group in northern New Brunswick indicates the presence of at least three mafic assemblages: two groups of basalts and gabbros and one group of gabbros only. The three groups can be separated on the basis of TiO2 and trace-element content. Group A basalts generally have mid-ocean-ridge basalt (MORB)-like compositions, whereas group B basalts indicate a "within-plate" setting (WPB). Group C gabbros intrude into silicic volcanics that underlie the basalts but are rare or absent in the areas underlain by group A and B basalts. The group C gabbros probably represent the earliest stages of mafic igneous activity and have MORB-like compositions or represent a transition between MORB and arc basalts.The association of group A and B basalts with abundant marine sediments, such as thinly bedded turbidites and black and red shales, and the fact that they erupted locally on top of continental-crust-derived silicic volcanics suggest that they represent a marginal-sea or back-arc-basin environment rather than true oceanic (Iapetus) eruptives as has been suggested.The proposed back-arc environment and existing structural data are inconsistent with previously proposed tectonic models and large-scale correlations. Evidence for penetrative pre-Late Ordovician (Taconic orogeny sensu stricto) deformation is lacking in the northern part of the Miramichi Zone. Instead the earliest folding and related thrusting (D1) is ascribed to deformation associated with closure of the back-arc basin in post-middle Caradocian times.

U–Pb ages, geochemistry, and tectonomagmatic history of the Cambro-Ordovician Annidale Group: a remnant of the Penobscot arc system in southern New Brunswick?1This article is one of a series of papers published in this CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology.

2012 ◽  
Vol 49 (1) ◽  
pp. 166-188 ◽  
Author(s):  
Susan C. Johnson ◽  
Leslie R. Fyffe ◽  
Malcolm J. McLeod ◽  
Gregory R. Dunning
Keyword(s):  
New Brunswick ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Conclusive Evidence ◽  
The Past ◽  
Late Cambrian ◽  
Suprasubduction Zone ◽  
History Of ◽  
Group A ◽  
Back Arc

The Penobscot arc system of the northeastern Appalachians is an Early Cambrian to early Tremadocian (ca. 514–485 Ma) ensialic to ensimatic arc–back-arc complex that developed along the margin of the peri-Gondwanan microcontinent Ganderia. Remnants of this Paleozoic arc system are best preserved in the Exploits Subzone of central Newfoundland. Correlative rocks in southern New Brunswick are thought to occur in the ca. 514 Ma Mosquito Lake Road Formation of the Ellsworth Group and ca. 497–493 Ma Annidale Group; however in the past, the work that has been conducted on the latter has been of a preliminary nature. New data bearing on the age and tectonic setting of the Annidale Group provides more conclusive evidence for this correlation. The Annidale Group contains subalkaline, tholeiitic to transitional, basalts to basaltic andesites, picritic tuffs and calc-alkaline to tholeiitic felsic dome complexes that have geochemical signatures consistent with suprasubduction zone magmatism that was likely generated in a back-arc basin. New U–Pb ages establish that the Late Cambrian to Early Tremadocian Annidale Group and adjacent ca. 541 Ma volcanic rocks of the Belleisle Bay Group in the New River belt were affected by a period of younger magmatism ranging in age from ca. 479–467 Ma. This provides important constraints on the timing of tectonism in the area. A ca. 479 Ma age for the Stewarton Gabbro that stitches the faulted contact between the Annidale and Belleisle Bay groups, demonstrates that structural interleaving and juxtaposition occurred during early Tremadocian time, which closely coincides with the timing of obduction of Penobscottian back-arc ophiolites onto the Ganderian margin in Newfoundland.

Age, chemistry, and tectonic setting of Miramichi terrane (Early Paleozoic) volcanic rocks, eastern and east-central Maine, USA

2021 ◽  
Vol 57 ◽  
pp. 239-273
Author(s):  
Allan Ludman ◽  
Christopher McFarlane ◽  
Amber T.H. Whittaker
Keyword(s):  
New Brunswick ◽  
Subduction Zone ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
East Central ◽  
Arc Volcanism ◽  
Middle Ordovician ◽  
Volcanic Suite ◽  
Back Arc

Volcanic rocks in the Miramichi inlier in Maine occur in two areas separated by the Bottle Lake plutonic complex: the Danforth segment (Stetson Mountain Formation) north of the complex and Greenfield segment to the south (Olamon Stream Formation). Both suites are dominantly pyroclastic, with abundant andesite, dacite, and rhyolite tuffs and subordinate lavas, breccias, and agglomerates. Rare basaltic tuffs and a small area of basaltic tuffs, agglomerates, and lavas are restricted to the Greenfield segment. U–Pb zircon geochronology dates Greenfield segment volcanism at ca. 469 Ma, the Floian–Dapingian boundary between the Lower and Middle Ordovician. Chemical analyses reveal a calc-alkaline suite erupted in a continental volcanic arc, either the Meductic or earliest Balmoral phase of Popelogan arc activity. The Maine Miramichi volcanic rocks are most likely correlative with the Meductic Group volcanic suite in west-central New Brunswick. Orogen-parallel lithologic and chemical variations from New Brunswick to east-central Maine may result from eruptions at different volcanic centers. The bimodal Poplar Mountain volcanic suite at the Maine–New Brunswick border is 10–20 myr younger than the Miramichi volcanic rocks and more likely an early phase of back-arc basin rifting than a late-stage Meductic phase event. Coeval calc-alkaline arc volcanism in the Miramichi, Weeksboro–Lunksoos Lake, and Munsungun Cambrian–Ordovician inliers in Maine is not consistent with tectonic models involving northwestward migration of arc volcanism. This >150 km span cannot be explained by a single east-facing subduction zone, suggesting more than one subduction zone/arc complex in the region.

scholarly journals Best technique for fixation of displaced transverse olecranon fractures: tension band wiring or plate fixation?

2020 ◽  
Vol 6 (5) ◽  
pp. 1012
Author(s):  
Lokesh Kumar Yogi ◽  
Gagandeep Mahi ◽  
C. R. Thorat ◽  
Moti Janardhan Naik
Keyword(s):  
Functional Outcome ◽  
Large Scale ◽  
Plate Fixation ◽  
Tension Band ◽  
Tension Band Wiring ◽  
Clinical Event ◽  
Dash Score ◽  
Group A ◽  
Group B ◽  
Olecranon Fractures

<p><strong>Background:</strong> Fractures of olecranon are common fractures in upper limb. Tension band wiring (TBW) and plate fixation (PF) are mostly used techniques but choice is based on type of fracture and surgeon’s preference.</p><p><strong>Methods:</strong>  A study assessed functional results in 28 patients that were enrolled after the clinical event of trauma has occurred. Patients were divided into two groups- Group (A) for TBW and Group (B) for PF; here gender, age and side of fracture were ignored. Post-operative functional outcome were evaluated by using the Mayo Elbow Performance (MEP) and the Disabilities of the Arm, Shoulder and Hand (DASH) score parameters.</p><p><strong>Results:<em> </em></strong>Mean (SD) union time as determined by postoperative radiographs was 8.5 (1.48) weeks for group (A) and 9 (2.08) weeks for group (B). Mean (SD) MEP score at 9 months in group (A) 84.28 (7.28) and 80.71 (10.92) in group (B). Mean (SD) DASH at 9 months in group (A) 12.2 (8.8) and 11.7 (10.4) in group (B). Complications were reported in group (A) 6 patient (42.85%) out of 14 patients and in group (B) 1 patient (7.14%) out of 14 patients.</p><p><strong>Conclusions:<em> </em></strong>The current study shows that there are no significant differences in functional outcome between both the study groups. Due to lesser complications, we recommend the plate fixation approach as the better choice for transverse displaced olecranon fractures. More large scale studies are required to further confirm our results.</p>

Abstract 17296: Arrhythmia Recurrence and Subsequent Heart Failure Hospitalization in Atrial Fibrillation Patients Undergoing Catheter Ablation: A Landmark Analysis From the Kansai Plus Atrial Fibrillation (KPAF) Registry

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Nobuaki Tanaka ◽  
KOICHI INOUE ◽  
Atsushi Kobori ◽  
Kazuaki Kaitani ◽  
Takeshi Morimoto ◽  
...  
Keyword(s):  
Heart Failure ◽  
Atrial Fibrillation ◽  
Catheter Ablation ◽  
Large Scale ◽  
Multicenter Observational Study ◽  
History Of ◽  
Group A ◽  
Group B ◽  
Af Recurrence

Background: Heart failure (HF) is the leading cause of death in patients with atrial fibrillation (AF). Radiofrequency catheter ablation (RFCA) of AF is effective for maintaining sinus rhythm though its impact on heart failure still remains controversial. Purpose: We sought to elucidate whether AF recurrence following RFCA was associated with subsequent HF hospitalizations. Methods: We conducted a large-scale, prospective, multicenter, observational study. A total of 4931 consecutive patients who underwent an initial RFCA for AF with longer than 1-year of follow-up in 26 centers were enrolled (average age, 64±10 years; non-paroxysmal AF, 35.7%). The median follow-up duration was 2.9 years. The primary endpoint was an HF hospitalization more than 1-year after the index RFCA. We compared the patients without AF recurrences (group A) to those with AF recurrences within 1-year post RFCA (group B). Results: The 1-year cumulative incidence of AF recurrences after a single procedure was 30.7% (group A=3418, group B=1513 patients). Group B had a lower body mass index (group A vs. group B,24.1±3.6 vs. 23.8±3.4 kg/m 2 , p=0.014), longer history of AF (1.9 vs. 3.1 years, p<0.0001), higher prevalence of non-paroxysmal AF (32.1% vs. 33.9%, p<0.0001), and valvular heart disease (5.9% vs. 7.8%, p=0.013). They also had a lower ejection fraction (63.7±9.4% vs. 62.8±9.6%, p=0.0043) and larger left atrial dimeter (39.7±6.6 vs. 40.6±7.0 mm, p<0.0001) on echocardiography. Hospitalizations for HF were observed in 57 patients (1.14%) more than 1-year after the RFCA and were significantly higher in group B than group A (group A vs. group B, 0.91% vs 1.72%, log-rank p=0.019). Conclusions: Among AF patients receiving RFCA, those with AF recurrences were at a greater risk of subsequent heart failure hospitalizations than those without AF recurrences. Recognition that AF recurrence following RFCA is a risk factor for a subsequent HF-related hospitalization is appropriate in clinical practice.

scholarly journals A COMPARATIVE STUDY OF YOGIC AND AYURVEDIC INTERVENTION IN THE MANAGEMENT OF TAMAKA SHWASA.

2019 ◽  
Vol 7 (5) ◽  
Author(s):  
Dr Arpan A. Bhatt ◽  
Dr Shweta Pandey ◽  
Dr Brajesh Singh ◽  
Dr Gauravi Vyas ◽  
Dr Gyanendra Datta Shukla ◽  
...  
Keyword(s):  
Peak Expiratory Flow ◽  
Flow Rate ◽  
Industrial Development ◽  
Large Scale ◽  
Intervention Group ◽  
Yoga Intervention ◽  
Asthmatic Patients ◽  
Group A ◽  
Expiratory Flow ◽  
Group B

Asthma is one of the commonest respiratory disease (as Jamnagar situated on sea coast has more moisture present in the air and polluting environment is increasing due to rapid industrial development i.e. industries using various chemicals/ pollutants, increases the incidences of Respiratory tract diseases) as well as a significant disease burden worldwide costing billions of dollars. The WHO estimates that there are between 15 and 20 million people with Asthma in India. The increase is likely to be particularly dramatic in India, which is projected to become the world’s most populous nation by 2050. An absolute 2% increase in the prevalence of Asthma in India would result in an additional 20 million people with the disease.  Anti-asthmatic drugs that are available in the market are expensive and have adverse effects. Thus, it is wise to look for an adjunct therapy to alleviate these problems. Therefore, the main aim of this study is to see the effect of Yoga on patterns of clinical features, peak expiratory flow rates and use of drugs in Asthmatic patients. Yoga intervention group (Group A) showed 70.58% reduction in the use of emergency medicine while it was 68.09% in Ayurvedic conventional group (Group B). There was a 24.93% increment in the PEFR in the Group A while only 16.49% in the Group B. There was statistically significant reduction in frequency and duration of Asthma attacks in both the Groups. Yoga exercise among Asthmatic patients resulted in a decreased number of attacks and use of drugs. It also shows significant improvement in the peak expiratory flow rate in Yoga intervention Group. Further large scale study is recommended. Keywords: Asthma, Yoga, Expiratory flow rate.

Characterization of Two Patient Groups with Acquired Idiopathic Thrombotic Thrombocytopenic Purpura, Defined by ADAMTS13 (n=195) and/or Classic Pentad (n=89).

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3505-3505
Author(s):  
Masanori Matsumoto ◽  
Ayami Isonishi ◽  
Seiji Kato ◽  
Hiromichi Ishizashi ◽  
Hideo Yagi ◽  
...  
Keyword(s):  
Thrombotic Thrombocytopenic Purpura ◽  
Large Scale ◽  
Laboratory Data ◽  
Normal Activity ◽  
Neurological Involvement ◽  
Thrombocytopenic Purpura ◽  
Young Infants ◽  
Wide Range ◽  
Group A ◽  
Group B

Abstract Abstract 3505 Poster Board III-442 [Aims] Thrombotic thrombocytopenic purpura (TTP) is a phenotype of thrombotic microangiopathies (TMAs), and now well defined by the congenital or acquired deficiency of ADAMTS13 activity (ADAMTS13:AC). But, it is also true that clinical diagnosis of TTP exists and can be made by classic “pentad”; the four clinical features mentioned below and fever. However, the comprehensive analyses on these two phenotypes of acquired idiopathic (ai-) TTP have not been done. [Patients and Methods] Nara Medical University is a Japan-wide referral center for TMAs via assaying ADAMTS13:AC. During July 1998 and December 2008, a database of registered 919 patients with TMAs was made (in press). TMAs were defined as having all of the followings: (i) microangiopathic hemolytic anemia (hemoglobin ≤12g/dL), (ii) thrombocytopenia (platelet count ≤100 × 109/L); and (iii) a variable severity of organ dysfunction (renal or neurological involvement) devoid of the stigmata of disseminated intravascular coagulation. Assays of ADAMTS13:AC and its inhibitor (ADAMTS13:INH) were performed by commercially available chromogenic act-ELISA (Tokyo-Vienna). In our database, 284 patients with ai-TTP were enrolled, in which 195 patients (group A) were diagnosed by severe deficiency (<3% of the normal) of ADAMTS13:AC due to the presence of ADAMTS13:INH, and 89 patients (group B) by classic pentad, whose ADAMTS13:AC was not severely deficient without ADAMTS13:INH; 72 patients in group B had moderate deficiency of ADAMTS13:AC (3∼<25 %), 14 mild deficiency (25∼<50%), and 3 normal activity (≥50%). [Results] (1) Age The age and number of ai-TTP patients, when the initial TTP-bouts developed, are shown in Figure. It is interesting to note a tremendously wide range of the age (from 8 mo. to 87 y.o.) at TTP-bouts in both the groups A and B. The largest incident peak was seen at the age of around 60 y.o., and the 2nd one at around 45 y.o. The patients of under 30 y.o. were far less common, but present with consistent proportions. Particularly, it was a surprise to note the presence of 5 young infants (2 female and 3 males) under 2 y.o., who belonged to group A. (2) Deficient or detectable ADAMTS13:AC vs age: Higher population of group A patients was found in those after 70 y.o. than before. (3) Gender: Number of female patients in group A was 105 (/195, 54%), and that of group B was 48 (/89, 54%). Male patients were more common after 55 y.o. (4) Laboratory data: Platelet counts in group A appeared to be lower than in group B (14.7 ± 14.7 vs 28.8 ± 23.5 × 109/uL, mean ± SD), and serum creatinine levels tended to be lower in group A than group B (1.3±1.3 vs 3.2 ± 3.4 mg/dL). [Conclusion] We characterized two phenotypes of ai-TTP (n=284); group A (195/284, 69%) closely associated with deficient ADAMTS13, and group B (89/284, 31%) without. Patients with group A were commonly found in under 65 y.o., and those with group B in above 70 y.o. Further, a large-scale analysis revealed the presence of 5 young infants with ai-TTP belonged to group A, a hitherto not well-characterized clinical entity. Disclosures: Fujimura: Baxter BioScience: Consultancy, Membership on an entity's Board of Directors or advisory committees.

scholarly journals Identity and Pathogenicity of Two Phytophthora Taxa Associated with a New Root Disease of Olive Trees

Plant Disease ◽  
2001 ◽  
Vol 85 (4) ◽  
pp. 411-416 ◽  
Author(s):  
Esperanza Sánchez-Hernández ◽  
Mónica Muñoz-García ◽  
Clive M. Brasier ◽  
Antonio Trapero-Casas
Keyword(s):  
High Sensitivity ◽  
Sensu Stricto ◽  
Temperature Growth ◽  
Optimum Growth Temperature ◽  
Phytophthora Spp ◽  
Group A ◽  
Pathogenicity Tests ◽  
Olive Trees ◽  
Group B ◽  
Contrast Group

Fifty-two Phytophthora isolates from necrotic roots of olives were characterized. Colony morphologies on carrot-agar medium led us to separate them into two groups: A (36 isolates) and B (16 isolates). The optimum growth temperature for Group A was about 21°C, with slow growth at 30°C. In contrast, Group B isolates had an optimum temperature for growth of 26°C, and grew rapidly at 30°C. Growth rates, sporangial and oogonial characteristics of the Group A isolates conformed to P. megasperma “BHR-type” sensu stricto. This designation was supported by a sequence analysis of their ITS rDNA regions. Colony patterns, sporangial characteristics and temperature-growth relationships of the Group B isolates conformed closely to those of the ‘O-group’ taxon of Phytophthora. They also conformed to this unusual taxon in their ITS sequence. In addition, Group B isolates were either entirely self-sterile, self-sterile A1s or weakly self-fertile. Pathogenicity tests showed that both taxa were highly aggressive on roots of olive trees. The association of flooding with Phytophthora infection indicates that the previously reported high sensitivity of olive to root asphyxiation may be more properly regarded as root-rot caused by Phytophthora spp.

scholarly journals A Comparative Clinical Study on the Effect of Dhanyaka Kalka and Dhanyaka Avalehya with Anupana of Sharkara mixed Tandulodaka in Garbhini Chardi

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Upasana Nath ◽  
Kalpana Sharma
Keyword(s):  
Clinical Study ◽  
Large Scale ◽  
Symptomatic Relief ◽  
First Trimester ◽  
Comparative Clinical Study ◽  
Group A ◽  
Group B ◽  
Rice Water ◽  
Trial Drug ◽  
In Pregnancy

Garbhini Chardi (vomiting in pregnancy) is a blazing issue in obstetric enactment. About 50-60% of all pregnant females agonize from vomiting in pregnancy most apparently in first trimester. If not tackled effectively before or in time, it may affect the quality of life of pregnant woman and pregnancy consequences. Ayurvedic classics have described many formulations for management of Garbhini Chardi. In this study Dhanyaka kalka and Dhanyaka Avaleha was taken both with Anupana of Sharkara mixed Tandulodaka. Aim: To compare the effect of Dhanyaka Kalka and Dhanyaka Avaleha with Anupana of Sharkara mixed with Tandulodaka in Garbhini Chardi. Materials and Methods: Single blind clinical study with pre‑test and post‑test was designed. 60 patients complaining of Chardi in 1st trimester were randomly divided into the two groups: Group A and Group B, each comprising of 30 patients. Medicine used for Group A was Dhanyaka Kalka with Anupana of Sharkara Mixed Tandulodaka (rice, water or gruel) and medicine used for Group B was Dhanyaka Avaleha with Anupana of Sharkara mixed Tandulodaka. Those cases, which were in regular follow ups for 5 weeks were taken for clinical study. The criteria of assessment were mainly on the symptomatic relief. Intermediate follow ups were recorded at interval of two weeks. Results: In Group A, overall percentage relief in chief complains was calculated as 59.44% whereas in Group B this value was 66.5%. Conclusion: In present clinical study efficacy of Dhanyaka Avaleha has been proven beneficial in comparison to Dhanyaka Kalka. The trial drug is highly significant in the management of Garbhini Chardi. This study needs to be done on large scale and for longer duration.

scholarly journals Zircon U–Pb Ages and Geochemistry of Granite Porphyries in the Yangla Cu Deposit, SW China: Constraints on Petrogenesis and Tectonic Evolution of the Jinshajiang Suture Belt

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-35 ◽  
Author(s):  
Bo Li ◽  
Xinfu Wang ◽  
Lijuan Du ◽  
Zuopeng Xiang ◽  
Guo Tang ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Large Scale ◽  
Tectonic Setting ◽  
Total Content ◽  
Mining District ◽  
Pressure Setting ◽  
Polymetallic Mineralization ◽  
Granite Porphyries ◽  
Geochemical Analyses ◽  
Element Enrichment

Located in the eastern part of the Tethyan tectonic domain, the Jinshajiang Suture Belt (JSB), northwestern Yunnan, China, is notable for its large-scale distribution of Jurassic to Triassic granitoids that are genetically related to the evolution of the Paleo-Tethys Ocean and polymetallic mineralization. In this study, geochronological and geochemical analyses were conducted on three samples of these granite porphyries (GPs) using laser ablation inductively coupled plasma mass spectrometry and zircon U–Pb aging to reveal ages of 213±15, 198.4±8.6, and 195.3±6.4 Ma, respectively. These ages are younger than the emplacement ages of the granodiorites, at 208–239 Ma, suggesting that magmatic activities in the Yangla mining district likely continued for ~44 Ma. These GPs are rich in large-ion lithophile elements such as Rb, Ba, Th, U, K, and La but are deficient in high field strength elements such as Ta, Nb, Ce, Zr, Hf, and Ti. Significant Pb enrichment and P depletion were noted, as were varying degrees of metallogenic element enrichment in the order of Cu>Pb>Zn. The total content of rare earth elements (ΣREEs) of the GPs is in the range of 50.41–127.27 ppm and the LREE/HREE ratio is in the rage of 4.46–10.54. The GPs are rich in LREEs, with a high degree of differentiation noted between the LREEs and HREEs. The δEu (EuN/Eu∗) and δCe (CeN/Ce∗) values, at 0.53–0.86 and 0.79–0.98, indicate weak and slightly weak negative anomalies, respectively. The geochemical characteristics of the GPs indicate that these bodies are slightly metaluminous to peraluminous S-type granites in a calc–alkaline series that formed in a late-collisional or postcollisional tectonic setting. Three-component mixing of magmas including those of upper crust, lower crust, and mantle materials in addition to subsequent partial melting could have been responsible for the generation of these GPs in an epithermal low-pressure setting at <5 kbar.

scholarly journals Morphometric analysis of early Eocene <i>Corbisema</i> skeletons (Silicoflagellata) in Mors, Denmark

2018 ◽  
Vol 37 (1) ◽  
pp. 283-293
Author(s):  
Hideto Tsutsui ◽  
Richard W. Jordan ◽  
Niichi Nishiwaki ◽  
Shiro Nishida
Keyword(s):  
Sensu Stricto ◽  
The Arctic ◽  
Ring Size ◽  
Geological Time ◽  
Basal Ring ◽  
Spine Length ◽  
Modern Species ◽  
Group A ◽  
Group B ◽  
The Relationship

Abstract. A two-dimensional morphometric programme, recently designed to measure fossil skeletons of the silicoflagellate genus Corbisema, was used to investigate specimens of the C. apiculata–C. triacantha complex found in a sample from the Fur Formation on the island of Mors, Jutland, Denmark. The semi-automated programme measured the lengths of the basal sides and radial spines, the basal side curvature, and the location of the pikes (if present) from a photographic database (N=469). As a result, two distinct morphological groups were revealed based on their radial spine length : basal side length ratio and the presence or absence of pikes: group A (ratio of 1 : 1.3, no pikes) and group B, with the latter subdivided into B1 (ratio of 1 : 7, with pikes) and B2 (ratio of 1 : 6, no pikes). Group A (C. triacantha sensu lato) possesses a small basal ring with relatively straight basal sides and long radial spines, while group B has a large basal ring with curved basal sides and short radial spines. In B1 specimens (C. apiculata sensu stricto) the pikes are positioned 0 to 1 µm away from the junction point of the strut and basal ring. This would suggest that B1 double skeletons are likely to be in the Star-of-David configuration, while A and B2 double skeletons (which lack pikes) are likely to be in the corner-to-corner configuration. Compared with the previously published biometric studies of extant Stephanocha (Stephanocha speculum complex in the Southern Ocean and S. medianoctisol in the Arctic Ocean), the results are somewhat different: although C. triacantha sensu lato (group A) is similar to the modern species of Stephanocha, the latter have smaller basal ring diameters, whereas specimens of C. apiculata sensu lato (types B1 and B2) have large basal rings. If their cell diameters are calculated, B1 is the largest, with S. speculum being the smallest – about half the size of B1. This could suggest that the relationship between radial spine length and mean basal ring size has shifted over geological time.

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