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Planothidium biporomum differs from other Planothidium species with a cavum, such as P. frequentissimum and P. potapovae, by the lanceolate valves with capitate ends. Planothidium incuriatum has subrostrate apices. Planothidium haynaldii has a depression, but not a cavum, on the internal surface of the central area. Planothidium sheathii has obtusely rounded, but not protracted apices. Rapheless valves should also be observed to confirm identification.

LM scalebar = 10 µm
Planothidium bipororum LM3 Planothidium bipororum LM1 Planothidium bipororum LM4
Length Range
12-25 µm
Width Range
5.4-7.0 µm
Striae in 10 µm
12-15

Planothidium incuriatum

Wetzel, Van de Vijver and Ector 2013

Planothidium Incuriatum LM4 Planothidium Incuriatum LM2 Planothidium Incuriatum LM3 Planothidium incuriatum LM1 Planothidium incuriatum LM2
Length Range
19-24 µm
Width Range
6.2-7.3 µm
Striae in 10 µm
13-15

Planothidium frequentissimum

(Lange-Bert. in Krammer and Lange-Bert.) Lange-Bert. 1999

Gs119780 1 Ed Planothidium frequentissimum LM3 Planothidium frequentissimum LM2 Mo000019 1A Ed 5 Planothidium frequentissimum LM1 Gs181995 1B Ed Mo000019  Plfreq 1B Ed
Length Range
5-17 µm
Width Range
3-6 µm
Striae in 10 µm
13-18

Planothidium potapovae

C.E.Wetzel and Ector 2019

Gsn23403  Plrostr 3 Gsn23403  Plrostr 2 Gsn23403  Plrostr 5 Gc48893A 1A
Length Range
11.0-17.5 µm
Width Range
5.0-6.0 µm
Striae in 10 µm
11-13

Planothidium amphibium

C.E.Wetzel, Ector and L.Pfister 2014

Planothidium haynaldii LM1 Planothidium haynaldii LM4 Planothidium haynaldii LM2 Planothidium haynaldii LM3 Planothidium haynaldii LM6 Planothidium haynaldii LM5 Planothidium haynaldii LM7
Length Range
9-25 µm
Width Range
4.8-7.0 µm
Striae in 10 µm
14-15

Planothidium sheathii

Stancheva 2019

Planothidium Sheathii Lm09 Planothidium Sheathii Lm10 Planothidium Sheathii Lm08 Planothidium Sheathii Lm01 Planothidium Sheathii Lm03 Planothidium Sheathii Lm06 Planothidium Sheathii Lm05
Length Range
14-29 µm
Width Range
6.3-8.8 µm
Striae in 10 µm
11-13