Planothidium calcar

Edlund in Edlund, Soninkhishig, Williams and Stoermer 2001      Category: Monoraphid
BASIONYM: Achnanthes calcar Cleve 1891

Planothidium biporomum


Planothidium delicatulum

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova -
Length Range: 9.7-21.2 µm
Width Range: 7.1-10.4 µm
Striae in 10 µm: 26-32


Valves are elliptical, sometimes slightly constricted in the center. The axial area is narrow and linear on the raphe valve; the axial area is narrow and rhomboid on the rapheless valve. The central area on both valves is asymmetric, expanded to valve margins and contains a hood. The raphe is straight with sigmoid terminal fissures. The striae are fine, uniseriate and radiate throughout both valves.

Original Description

Basionym: Achnanthes calcar
Author: Cleve 1891
Length Range: 12 µm
Width Range: 9 µm
Striae in 10 µm: 24

Original Description

A. Calcar Cl. - Upper valve broadly elliptic, 0,012 m. m. in length and 0,009 m. m. in breadth, with about 24 striae in 0,01 m. m. It carries on the one side a horseshoe-like thickening, which is prolonged on the other half of the valve into a spur-like projection. The lower valve is not known with certainty, but in the same gathering, in which this species has been found, occurs a valve of similar outline and size, the striæ of which reach the raphe and are 25 in 0,01 m. m. That valve, which has a greta resemblance to Diadesmis lucidula Grun. (V. H. XIV, 40) may possibly be the lower valve of A. Calcar. Pl. III, fig. 8, (9 ?). Ab. 45, 47.

Original Images

Cite This Page:
Potapova, M. (). Planothidium calcar. In Diatoms of the United States. Retrieved February 11, 2016, from

Species: Planothidium calcar

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Cleve, P.T. (1891). The Diatoms of Finland. Actas Societas Pro Fauna et Flora Fennica 8 (2): 1-68.

Edlund, M.B., Soninkhishsig, N., Williams, R.M. and Stoermer, E.F. (2001). Biodiversity of Mongolia: Checklist of diatoms, including new distributional reports of 31 taxa. Nova Hedwigia 72(1-2):59-90.

Round, F. E. and Bukhtiyarova, L. (1996). Four new genera based on Achnanthes (Achnanthidium) together with a re-definition of Achnanthidium. Diatom Research 11: 345-361.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Planothidium calcar CAS

North American Diatom Ecological Database (NADED)

NADED ID: 155033

Autecology Discussion

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Planothidium calcar

EMAP Response Plots

Planothidium calcar

EMAP citations

Results are published in:

Johnson, T., Hermann, K., Spaulding, S., Beyea, B., Theel, C., Sada, R., Bollman, W., Bowman, J., Larsen, A., Vining, K., Ostermiller, J., Petersen, D. Hargett, E. and Zumberge, J. (2009). An ecological assessment of USEPA Region 8 streams and rivers. U.S. Environmental Protection Agency Region 8 Report, 178 p.

Stoddard, J. L., Peck, D. V., Olsen, A. R., Larsen, D. P., Van Sickle, J., Hawkins, C. P., Hughes, R. M., Whittier, T. R., Lomnicky, G. A., Herlihy, A. T., Kaufman, P. R., Peterson, S. A., Ringold, P. L., Paulsen, S. G., and Blair, R. (2005). Environmental Monitoring and Assessment Program (EMAP) western streams and rivers statistical summary. U.S. Environmental Protection Agency Report 620/R-05/006, 1,762 p.

Stoddard, J. L., Peck, D. V., Paulsen, S. G., Van Sickle, J., Hawkins, C. P., Herlihy, A. T., Hughes, R. M., Kaufman, P. R., Larsen, D. P., Lomnicky, G. A., Olsen, A. R., Peterson, S. A., Ringold, P. L., and Whittier, T. R. (2005). An ecological assessment of western streams and rivers. U.S. Environmental Protection Agency Report 620/R-05/005, 49 p.