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Pinnularia torta also has large, linear valves and a asymmetric axial area. Pinnularia torta is smaller, with a more linear central valve and ends, finer striae and more asymmetric axial area.

Pinnularia flexuosa has linear valves, with straight sides and less radiate striae in the central valve.

Pinnularia ectorii has a more expanded central valve; the valves are not as linear.

LM scalebar = 10 µm
Pinnularia nobilis ANSP BOY738 85 Pinnularia nobilis ANSP BOY738 71 Pinnularia nobilis ANSP BOY738 72 Pinnularia nobilis ANSP BOY738 51 Pinnularia nobilis ANSP BOY738 84 Pinnularia nobilis ANSP BOY738 75 Pinnularia nobilis ANSP BOY738 66
Length Range
200-270 µm
Width Range
32.5-39 µm
Striae in 10 µm
5

Pinnularia torta

(A.Mann) R.M.Patrick 1966

Pinnularia torta LM3 Pinnularia torta LM7 Pinnularia torta LM2 Pinnularia torta LM4 Pinnularia torta LM5 Pinnularia torta LM1 Pinnularia torta LM6
Length Range
160.3-256 µm
Width Range
24-31 µm
Striae in 10 µm
7-8

Pinnularia ectorii

Potapova, Aycock and Kersey 2023

Pinnularia ectorii LM5 Pinnularia ectorii LM6 Pinnularia ectorii LM6 Pinnularia ectorii LM3 Pinnularia ectorii LM4 Pinnularia ectorii LM1 Pinnularia ectorii LM2
Length Range
185–335 µm
Width Range
29–44 µm
Striae in 10 µm
5–6 throughout the valve, up to 9 around central area

Also compare to

Pinnularia flexuosa

Cleve