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Pseudostaurosira americana

E.Morales 2005      Category: Araphid
BASIONYM: Fragilaria americana E.Morales 2005

REPORTED AS: Pseudostaurosira subsalina (Morales 2005, pg. 115, Figs. 1–20, 80-85) 

Pseudofallacia tenera


Pseudostaurosira brevistriata

LM scalebar = 10 µm = 80 pixels.


Contributor: Eduardo A. Morales | Barry Rosen | Sarah Spaulding - March 2013
Length Range: 6-38 µm
Width Range: 4.5-5.0 µm
Striae in 10 µm: 16-18


Valves linear to elliptic, with cuneate to rounded ends. The central area is linear to lanceolate. The valve face connects sharply with the mantle. The abvalvar edge of the mantle is parallel to the valve face/mantle junction. In girdle view, frustules are rectangular. Cells often form short ribbon-like colonies, joined by linking spines. The axial area is narrow and linear or, less frequently, slightly lanceolate. Striae are distinctly punctate and composed of square to round areolae, decreasing in size from valve face/mantle junction to axial area. Striae are slightly alternate (referring to how striae from opposite margins “meet” at the central sternum). Areolae bear branched volae. Areolae on the valve mantle may bear flaps partially occluding the external areolar opening. The striae are interrupted at the valve face/mantle junction by spines. Costae are broader than the striae. Spines are flat, spatulate and solid. Spines are present along the valve face edge, except at the apices. Conspicuous scar-like depositions are present along abvalvar edge of valve mantle. Reduced apical pore fields with round poroids ocellulimbus type) are present at both valve ends. Pore fields are located at the junction between the valve face and mantle. Rimoportulae are absent. Copulae, or girdle bands, are open and do not bear perforations. Valvocopulae are wider than other girdle elements.

Original Description

Basionym: Fragilaria americana
Author: E.Morales 2005
Length Range: 6-22 µm
Width Range: 4.5-5.0 µm
Striae in 10 µm: 16-18

Original Description

DESCRIPTION: Frustula aspectu cingulari rectangularia in catenis. Valvae isopolares lanceolatae apicibus cuneatis, 6–22 mm longae, 4.5–5.0 mm latae. Striae 16–18 in 10 mm, uniseriatae alternae parallelae. Duae ad quinque areolae in quoque stria. Sternum angustum lineare. Volae projecturis ramosis ex areolarum parietis. Spinae spatulatae. Area porellarum ad apices cum duabus seriebus poris. Rimoportulae nullae.

Original Images

Cite This Page:
Morales, E., Rosen, B., and Spaulding, S. (2013). Pseudostaurosira americana. In Diatoms of the United States. Retrieved May 22, 2018, from

Species: Pseudostaurosira americana

Contributor: Eduardo A. Morales | Barry Rosen | Sarah Spaulding

Reviewer: Sam Rushforth


Cejudo-Figueiras, C., Morales, E.A., Wetzel, C.E., Blanco, S., Hoffmann, L., and Ector, L. (2011). Analysis of the type of Fragilaria construens var. subsalina (Bacillariophyceae) and description of two morphologically related taxa from Europe and the United States. Phycologia 50:(1) 67-77.

Hustedt, F. (1925). Bacillariales aus den Salzgewässern bei Oldesloe in Holstein. Mitteilungen der geographischen Gesellschaft und der Naturhistorischen Museums in Lubeck, zweite Reihe 30: 84-121.

Morales, E.A. (2005). Observations of the morphology of some known and new fragilarioid diatoms (Bacillariophyceae) from rivers in the USA. Phycological Research 53: 113-133.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Pseudostaurosira americana CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Pseudostaruosira americana has been reported from circumneutral water (pH 7.5), with low to medium concentrations of orthophosphate (0.24 mgl/l) and total nitrogen (0.490 mg/l) and moderate specific conductance (238 µS/cm) (Morales 2005).