Compare

Stephanodiscus parvus has a prominent central fultoportula and a weakly undulate valve face. Stephanodiscus binderanus and S. hantzschii are quite distinct, as they both have a flat valve face. Cyclostephanos tholiformis has a central annulus and a higher density of areolae. Stephanodiscus oregonicus has larger valves, multiseriate fascicles and variation in interfascicle shape.

LM scalebar = 10 µm
Stephanodiscus minutulus LM1 Stephanodiscus minutulus LM2 Stephanodiscus minutulus LM3 Stephanodiscus minutulus LM4 Stephanodiscus minutulus LM5
Diameter
6-10 µm
Striae in 10 µm
8-13 based on circumferential density

Stephanodiscus binderanus

(Kütz.) Krieger 1927

Stephanodiscus binderanus LM7 Stephanodiscus binderanus LM6 Stephanodiscus binderanus LM5 Stephanodiscus binderanus LM4 Stephanodiscus binderanus LM1 Stephanodiscus binderanus LM2 Stephanodiscus binderanus LM3
Diameter
6.3-11.8 µm
Width Range
2.6-4.7 µm
Striae in 10 µm
10 to 15 based on circumferential density

Stephanodiscus parvus

Stoermer and Håk. 1984

Stephanodiscus parvus LM7 Stephanodiscus parvus LM6 Stephanodiscus parvus LM5 Stephanodiscus parvus LM4 Stephanodiscus parvus LM2 Stephanodiscus parvus LM1
Diameter
4.3-9.5 µm
Striae in 10 µm
8-12 based on circumferential count

Stephanodiscus hantzschii

Grunow in Cleve and Grunow 1880

Stephanodiscus hantzschii LM7 Stephanodiscus hantzschii LM4 Stephanodiscus hantzschii LM3 Stephanodiscus hantzschii LM6 Stephanodiscus hantzschii LM1
Diameter
11.8-20.3 µm
Striae in 10 µm
6-9 fascicles based on circumferential count

Stephanodiscus oregonicus

(Ehrenb.) Håk. 1986

Stephanodiscus oregonicus LM7 Stephanodiscus oregonicus LM6 Stephanodiscus oregonicus LM5 Stephanodiscus oregonicus LM4 Stephanodiscus oregonicus LM3 Stephanodiscus oregonicus LM2 Stephanodiscus oregonicus LM1
Diameter
13.0-25.6 µm

Also compare to

Cyclostephanos tholiformis

Stoermer, Håk. and E.C.Ther.