Compare

Aulacoseira subarctica is similar in cell size and proportions to A. ambigua, but does not have a hollow ringleiste and has large pointy spines with a row of mantle areolae running into the middle of each spine. Linking spines of A. ambigua are small, bifurcated or triangular and are easily distinguished from the pointy spines of A. subarctica, but the separation spines of A. ambigua can be difficult to distinguish from those of A. subarctica under LM. Often the rows of mantle areolae in A. ambigua merge close to valve face and thus give an impression of a single row of areolae running into the base of the spine as in A. subarctica, but the spines of A. subarctica are larger than separation spines in A. ambigua and even if two rows of mantle areolae merge into a single row that runs into the base of the spine, this merge happens far from the valve face. A. subarctica is similar in frustule structure to A. pusilla, which has, however, lower mantle height/valve diameter ratio and shorter spines. The initial and post-initial cells of A. subarctica can also have a low (0.4-0.8) mantle height/valve diameter ratio, but they are larger in diameter (> 7.5 mm) than valves of A. pusilla.

LM scalebar = 10 µm
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

Aulacoseira ambigua

(Grunow) Simonsen 1979

Aulacoseira ambigua LM5 Aulacoseira ambigua LM6 Aulacoseira ambigua LM3 Aulacoseira ambigua LM4 Aulacoseira ambigua LM7 Aulacoseira ambigua LM1 Aulacoseira ambigua LM2
Diameter
3-12 µm
Width Range
5-15 µm
Striae in 10 µm
17-22

Aulacoseira pusilla

(Meister) Tuji and Houk 2004

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