Populations of S. amphicephala from the Northern Rockies (Montana Diatom Collection) overlap in size with S. clandestina, raising the question whether these are indeed two separate taxa. Stauroneis amphicephala is considerably larger than S. reichardtii, which has more linear valves. Stauroneis anceps has narrow, rostrate apices. Valves of S. ancepsfallax have capitate apices and are more lanceolate.

LM scalebar = 10 µm
Stauroneis amphicephala LM5 Stauroneis amphicephala LM4 Stauroneis amphicephala LM3 Stauroneis amphicephala LM2 Stauroneis amphicephala LM1 Stauroneis amphicephala LM6
Length Range
55-82 µm
Width Range
11.0-16.8 µm
Striae in 10 µm

Stauroneis reichardtii

Lange-Bert., Cavacini, Tagliaventi, and Alfinito 2003

Stauroneis reichardtii LM6 Stauroneis reichardtii LM4 Stauroneis reichardtii LM5 Stauroneis reichardtii LM3 Stauroneis reichardtii LM2 Stauroneis reichardtii LM1
Length Range
36-54 µm
Width Range
8.0-10.8 µm
Striae in 10 µm

Stauroneis anceps

Ehrenb. 1843

Stauroneis anceps LM7 Stauroneis anceps LM6 Stauroneis anceps LM5 Stauroneis anceps LM2 Stauroneis anceps LM4 Stauroneis anceps LM3 Stauroneis anceps LM1
Length Range
48-76 µm
Width Range
12-15 µm
Striae in 10 µm

Stauroneis ancepsfallax

L.L.Bahls 2010

Stauroneis ancepsfallax LM6 Stauroneis ancepsfallax LM5 Stauroneis ancepsfallax LM4 Stauroneis ancepsfallax LM3 Stauroneis ancepsfallax LM2 Stauroneis ancepsfallax LM1
Length Range
52-70 µm
Width Range
11.4-14.2 µm
Striae in 10 µm

Also compare to

Stauroneis clandestina

Lange-Bert. and Van de Vijver