Compare

Gomphonema apuncto is very narrow and linear. Gomphonema lousiananum is smaller, ranging from 3.8 to 5.5 ┬Ám in width. It also has relatively a wider axial area, that is, the striae are closer to the valve margin. Gomphonema stoermeri, G. freesei and G. amerhombicum all possess stigmoids.

LM scalebar = 10 µm
Gomphonema christenseni LM2 Gomphonema christenseni LM5 Gomphonema christenseni LM6 4 53920  Gchristenseni Holo 5 53920  Gchristenseni2 6 53920  Gchristenseni2 7 53920  Gchristenseni2
Length Range
32.8-57.4 µm
Width Range
6.1-7.8 µm
Striae in 10 µm
13-16

Gomphonema apuncto

J.H.Wallace 1960

Gomphonema apuncto LM4 Gomphonema apuncto LM1 Gomphonema apuncto LM3 Gomphonema apuncto LM2 Gomphonema apuncto LM5
Length Range
21.0-30.7 µm
Width Range
3.0-4.1 µm
Striae in 10 µm
13-16

Gomphonema louisiananum

Kalinsky 1984

Gomphonema louisiananum LM1 Gomphonema louisiananum LM2 Gomphonema louisiananum LM3 Gomphonema louisiananum LM4 Gomphonema louisiananum LM5 Gomphonema louisiananum LM6 Gomphonema louisiananum LM7
Length Range
13.5-38.3 µm
Width Range
3.8-5.5 µm
Striae in 10 µm
11-12 at the valve center, 14-16 at the apices

Gomphonema freesei

R.L.Lowe and Kociolek 1984

Gc53921  Gomphonema Freesei 1 Gc53921  Gomphonema Freesei 2 Gc53921  Gomphonema Freesei 3 Gc53921  Gomphonema Freesei 4 Holotype Gc53921  Gomphonema Freesei 4B Holotype Gc53921  Gomphonema Freesei 5
Length Range
35.0-53.9 µm
Width Range
6.5-7.5 µm
Striae in 10 µm
12.1-14.5 at valve center, 14.2-16.2 at headpole, 11.7-15.4 at footpole

Gomphonema amerhombicum

E.Reichardt 2007

G Amerhombicum  B Isotype 20170301 06 Cl G Amerhombicum  A Isotype 20170301 08 Cl G Amerhombicum  A Isotype 20170301 18 Cl G Amerhombicum  B Isotype 20170301 05 Cl G Amerhombicum  B Isotype 20170301 14 Cl G Amerhombicum  B Isotype 20170301 09 Cl G Amerhombicum  B Isotype 20170301 21 Cl
Length Range
22.5-60 µm
Width Range
5.6-7.7 µm
Striae in 10 µm
13-15 at mid-valve, up to 17 at headpole

Also compare to

Gomphonema stoermeri

Kociolek and Kingston