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Stauroneis anceps

Ehrenb. 1843      Category: Symmetrical biraphid

Stauroneis amphicephala


Stauroneis ancepsfallax

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - November 2011
Length Range: 48-76 µm
Width Range: 12-15 µm
Striae in 10 µm: 19-21


Valves are lanceolate to linear-lanceolate. The apices are protracted and narrowly rostrate. The axial area is moderately wide and linear, expanding slightly near the central area. The central area (in Northern Rockies specimens) is a narrow rectangular stauros, hardly expanded toward valve margins and sometimes with shortened striae. The raphe is lateral. Proximal raphe ends are weakly expanded, weakly deflected, and widely spaced (they do not extend into the central area). Striae are radiate throughout. Areolae are variably spaced and number 20-28 in 10 µm.

Stauroneis anceps is one of the most commonly misidentified Stauroneis species in North America. Reichardt (1995) designated the lectotype for this species (Tafel 16, fig. 1) from a population (Sippe 1) in Ehrenberg’s type material from Cayenne, French Guyana. Similar forms present in Ehrenberg’s type material (Sippe 2 and Sippe 3) were later described as Stauroneis reichardtii (Lange-Bertalot et al. 2003). Specimens of S. anceps from the Northern Rockies tend to be somewhat larger, have a lower stria density and a smaller stauros than specimens of Sippe 1 in the type population, but they are otherwise quite similar. Until further work is completed, we consider the population of S. anceps described here to represent this species as described by Reichardt (1995) from Ehrenberg’s type material.

Original Description

Author: Ehrenb. 1843
Length Range: 40-70 µm
Width Range: 10-13 µm
Striae in 10 µm: 22-24

Original Description

Original Images

Cite This Page:
Bahls, L. (2011). Stauroneis anceps. In Diatoms of the United States. Retrieved May 23, 2018, from

Species: Stauroneis anceps

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


Bahls, L. (2010). Stauroneis in the Northern Rockies: 50 species of Stauroneis sensu stricto from western Montana, northern Idaho, northeastern Washington and southwestern Alberta, including 16 species described as new. Northwest Diatoms, Volume 4. The Montana Diatom Collection, Helena, 172 pp.

Ehrenberg, C.G. (1843). Verbreitung und Einfluß des mikroskopischen Lebens in Süd- und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin, 1841: 291-445, 4 Tafel.

Lange-Bertalot, H., Cavacini, P., Tagliaventi, N. and Alfinito, S. (2003). Diatoms of Sardinia: Rare and 76 new species in rock pools and other ephemeral waters. Iconographia Diatomologica 12, 438 pp.

Reichardt, E. (1995). Die Diatomeen (Bacillariophyceae) in Ehrenbergs Material von Cayenne, Guyana Gallica (1843). Volume 1, Iconographia Diatomologica (H. Lange-Bertalot, ed.). Koeltz Scientific Books, Konigstein.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Stauroneis anceps CAS

NCBI Genbank Taxonomy

Stauroneis anceps NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 62002

Autecology Discussion

In the Northern Rockies, Stauroneis anceps is found in lakes and ponds with circumneutral pH (mean pH = 6.9) and very low specific conductance (mean SC = 17 µS/cm).


Bloody Dick Pond #2, Beaverhead County, Montana: Home of Stauroneis anceps

Credit/Source: Loren Bahls

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

Stauroneis anceps

EMAP Response Plots

Stauroneis anceps

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.