Stephanodiscus niagarae is smaller and has a higher areola density (11-20 in 10 µm) than S. reimeri, which is larger and has 8-12 areolae in 10 µm.

Stephanodiscus alpinus has spines at the end of nearly every costa and the interfascicles are 8-11 in 10 µm.

Stephanodiscus neoastraea differs by having scattered areolae in the center, lacks central fultoportulae and the interfascicles are 7-9 in 10 µm.

Stephanodiscus niagarae differs from S. yellowstonensis by having greater numbers of spines at similar valve diameter and more regular spine placement on every second or third costae versus spines on every second to fifth costae in S. yellowstonensis.

LM scalebar = 10 µm
Ill2011 41  Steph Niagarae6 Ill2011 41  Steph Niagarae5 Ill2011 41  Steph Niagarae2 Ill2011 41  Steph Niagarae3 Ill2011 41  Steph Niagarae
21-70 µm

Stephanodiscus reimeri

E.C.Ther. and Stoermer 1992

Stephanodiscus reimeri LM3 Stephanodiscus reimeri LM7 Stephanodiscus reimeri LM6 Stephanodiscus reimeri LM1 Stephanodiscus reimeri LM4
35-120 µm

Stephanodiscus yellowstonensis

E.C.Ther. and Stoermer 1984

Stephanodiscus yellowstonensis LM7 Stephanodiscus yellowstonensis LM6 Stephanodiscus yellowstonensis LM4 Stephanodiscus yellowstonensis LM2 Stephanodiscus yellowstonensis LM1 Stephanodiscus yellowstonensis LM5 Stephanodiscus yellowstonensis LM3
33-66 µm

Stephanodiscus alpinus

Hust. in Hub.-Pest. 1942

Stephanodiscus alpinus LM3 Stephanodiscus alpinus LM7 Stephanodiscus alpinus LM2 Stephanodiscus alpinus LM11 Stephanodiscus alpinus LM6 Stephanodiscus alpinus LM5 Stephanodiscus alpinus LM4
13.8-30.8 µm
Striae in 10 µm
12-14 fascicles

Also compare to

Stephanodiscus superiorensis

Stoermer and E.C.Ther.

Stephanodiscus neoastraea

Hȧk. and B.Hickel 1986