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Pinnularia rhombarea

Krammer in Metzeltin and Lange-Bert. 1998      Category: Symmetrical biraphid

Pinnularia rabenhorstii


Pinnularia saprophila

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - March 2014
Length Range: 45-75 µm
Width Range: 10.2-12.5 µm
Striae in 10 µm: 9-11


Valves are linear with parallel or slightly convex margins. The apices are barely subrostrate, so that they are just a bit narrower than the valves. The apices broadly rounded.. The axial area is narrow and widens abruptly just short of the central area. The central area is a rhombus, which is open on both sides to form a transverse fascia. The slightly curved raphe is weakly lateral and slightly complex. Proximal raphe ends are deflected to one side and terminate in small pores. Distal raphe fissures are shaped like commas or question marks. The terminal raphe fissures are surrounded by striae at the poles. The striae are strongly radiate near the valve center, becoming strongly convergent near the apices.

Original Description

Author: Krammer in Metzeltin and Lange-Bert. 1998
Length Range: 40-100 µm
Width Range: 10.5-16.0 µm
Striae in 10 µm: 9-11

Original Description

NOTE: the original description in Metzeltin and Lange-Bertalot (1998) was emended by Krammer (2000). Both the original and emended descriptions are provided here.

Original Images

Cite This Page:
Bahls, L. (2014). Pinnularia rhombarea. In Diatoms of the United States. Retrieved May 23, 2018, from

Species: Pinnularia rhombarea

Contributor: Loren Bahls

Reviewer: Marina Potapova


Krammer, K. (2000). The genus Pinnularia. The Diatoms of Europe. Diatoms of Inland Waters and Comparable Habitats 1: 1-703.

Metzeltin, D. and Lange-Bertalot, H. (1998). Tropical diatoms of South America I: About 700 predominantly rarely known or new taxa representative of the neotropical flora. In: Lange-Bertalot, H. (ed.), Iconographia Diatomologica. Annotated Diatom Micrographs. Vol. 5. Diversity-Taxonomy-Geobotany. Koeltz Scientific Books. Königstein, Germany, 5:695 pp.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Pinnularia rhombarea CAS

North American Diatom Ecological Database (NADED)

NADED ID: 52815

Autecology Discussion

Pinnularia rhombarea is common in ponds and small lakes in the northern Rocky Mountains of Montana. Specimens shown on this web page are from Meadow Lake, in Missoula County. Meadow Lake has a pH of 7.5 and specific conductance of 10 µS/cm. Krammer (2000) reports P. rhombarea from northern and subarctic regions in cold oligotrophic waters with low electrolyte content.


Atlantic Pond, Glacier National Park, Montana: home of Pinnularia rhombarea.

Credit/Source: Loren Bahls