| Valve outline | oval-elliptic slightly heteropolar | broadly elliptic to almost rounded | ovate | ovate | oval-elliptic | rhombic-lanceolate to egg-shaped-lanceolate | oval to linear-oval |
|---|
| Head pole | rounded | broadly rounded | broadly rounded | broadly rounded | broadly rounded | wedge-shaped and rounded | narrowly rounded |
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| Foot pole | narrowly rounded, rarely slightly protracted | rounded in smaller valves, cuneate in larger valves | rounded in smaller valves, cuneate in larger valves | rounded to narrowly cuneate | cuneate | wedge-shaped and rounded | narrowly rounded, rarely slightly protracted |
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| Valve length (μm) | 37.0–47.0 | 18.0–70.0 | 13.0–56.0 | 19.0–30.0 | 19.0–28.0 | 16.0–120.0 | 15.0–48.0 |
|---|
| Valve width (μm) | 15.0–17.5 | 12.0–30.0 | 10.0–24.0 | 10.0–13.0 | 10.0–11.0 | 12.0–45.0 | 8.0–16.0 |
|---|
| Length-to-width ration | 2.3–2.7 | 1.4–1.7 | (1.5)2.0–2.2 | 2.2–2.5 | 2.0–2.4 | 3.1-1.1 | 2.5–3.0 |
|---|
| Costae density (in 10 µm) | 18 | 18–23 | -- | 9 | 8 | 3.5–6 | -- |
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| Striae density (in 10 μm) | 18–21 | 16–20 | 18–23 | 27–33 | 28–30 | 16–19 | 10–13 |
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| Areolae density (in 10 µm) | 90–110 | -- | -- | 80 – 115 | -- | -- | -- |
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| Axial area | narrow, linear | linear-elliptic or elliptic in smaller valves, cuneate in larger valves | linear-elliptic or elliptic in smaller valves, cuneate in larger valves | narrowly cuneate | narrowly cuneate | cuneate | narrow, linear |
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| Portulae | (1) 3–4 between two fibulae; 1 to 3 striae per portula | -- | (1) 3–4 between two fibulae; 1–2 striae per portula | 1 between two fibulae; 2 striae per portula | 1–3 between two fibulae; 1–2 striae per portula | -- | -- |
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| Reference | this study | Lange-Bertalot et al. 2017 | English & Potapova 2012 | English & Potapova 2012 | Reichardt 2012 | Lange-Bertalot et al. 2017 | Lange-Bertalot et al. 2017 |
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