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Aulacoseira pusilla differs from several Aulacoseira species with low-mantles by having curved pervalvar rows of areolae and a distinct, shelf-like ringleiste. Aulacoseira alpigena has similar frustule proportions, size, mantle rows of areolae and ringleiste to A. pusilla, but differs by having thin spines at the end of each costa. Furthermore, the valves of A. pusilla have thick spines that originate from two or three pervalvar costae. The frustule structure of A. pusilla is similar to that of A. subarctica, but the latter species has a higher mantle, a high ratio of mantle height to valve diameter, and longer spines. Aulacoseira distans has a much lower density of mantle rows of areolae, the valve face is covered by areolae, thin spines are positioned at the end of each costa, a deep ringleiste is present, and numerous (4-12) prominent rimoportulae are visible in LM (in valve view). In the past, A. pusilla has been misidentified as A. distans, which is probably an extinct species.

LM scalebar = 10 µm
Aulacoseira pusilla LM3 Aulacoseira pusilla LM4 Aulacoseira pusilla LM5 Aulacoseira pusilla LM6 Aulacoseira pusilla LM1 Aulacoseira pusilla LM2
Diameter
4.5-7.5 µm
Width Range
2.2-4.5 µm
Striae in 10 µm
24-26

Aulacoseira alpigena

(Grunow) Krammer 1991

Aulacoseira alpigena LM2 Aulacoseira alpigena LM1 Aulacoseira alpigena LM4 Aulacoseira alpigena LM3 Aulacoseira alpigena LM5 Aulacoseira alpigena LM6 Aulacoseira alpigena LM7
Diameter
4-15 µm
Width Range
4-7 µm
Striae in 10 µm
15-22

Aulacoseira subarctica

(O.Müll.) E.Y.Haw. 1990

Aulacoseira subarctica LM2 Aulacoseira subarctica LM3 Aulacoseira subarctica LM1 Aulacoseira subarctica LM4 Aulacoseira subarctica LM5 Aulacoseira subarctica LM6 Aulacoseira subarctica LM7
Diameter
3-14 µm
Width Range
2.5-14 µm
Striae in 10 µm
15-22

Also compare to

Aulacoseira distans

(Ehrenb.) Simonsen