Achnanthes longboardia is more lanceolate in shape than A. coarctata, A. mauiensis, A. muelleri and A. inflata. The stria density of A. polynesia is higher.

LM scalebar = 10 µm
Achnanthes longboardia LM2 Achnanthes longboardia LM7 Achnanthes longboardia LM3 Achnanthes longboardia LM1 Achnanthes longboardia LM6 Achnanthes longboardia LM4 Achnanthes longboardia LM5
Length Range
22.6-47.8 µm
Width Range
8-10.5 µm
Striae in 10 µm
13-15 on raphe valve, 12-14 on rapheless valve

Achnanthes coarctata

(Bréb. ex W.Sm.) Grunow in Cleve and Grunow 1880

Achnanthes coarctata LM4 Achnanthes coarctata LM2 Achnanthes coarctata LM1 Achnanthes coarctata LM5 Achnanthes coarctata LM3
Length Range
32-70 µm
Width Range
9.4-15 µm
Striae in 10 µm
11 on the raphe valve, 9-10 on the rapheless valve

Achnanthes mauiensis

R.L.Lowe and A.R.Sherwood 2009

Achnanthes mauiensis LM1 Achnanthes mauiensis LM3 Achnanthes mauiensis LM5 Achnanthes mauiensis LM7 Achnanthes mauiensis LM4 Achnanthes mauiensis LM2 Achnanthes mauiensis LM6
Length Range
22.4-27.1 µm
Width Range
5-7.5 µm
Striae in 10 µm
15-19 on both valves

Achnanthes inflata

(Kütz.) Grunow 1867

Achnanthes inflata LM7 Achnanthes inflata LM1 Achnanthes inflata LM2 Achnanthes inflata LM3 Achnanthes inflata LM4 Achnanthes inflata LM5 Achnanthes inflata LM6
Length Range
32-59 µm
Width Range
13.5–21.1 µm
Striae in 10 µm

Also compare to

Achnanthes muelleri


Achnanthes polynesia

Lange-Bert. and Werum