• Category
  • Length Range
    4-10 µm
  • Width Range
    3-4 µm
  • Striae in 10 µm



Valves are ovoid, 3-4 µm wide and 4-10 µm long with rounded ends. Valve face flat, or slightly undulate due to raised costae. In girdle view, frustules are rectangular and form ribbon-like colonies, joined by linking spines. Colonies are attached to the substratum at one end by a frustule with a a mucilage pad, or colonies may be planktonic. Axial area is linear to lanceolate. Striae are distinct, 11-14 in 10 µm. Lineolae are long forming wide striae . Striae vary from parallel in the valve center to radiate toward the valve ends. Striae extend onto the valve mantle. Costae are more slender than the striae. Spines are positioned on costae along the valve margin, except at the apices. Spines are conical at the base and spatulate towards the terminus. A single apical pore field with round poroids is present, displaced toward valve mantle. Girdle bands are open and do not bear perforations.

Samples collected from North America exhibit several morphological variants that are often included under the name Staurosirella pinnata. Since the type of this taxon has not been studied in detail, it is difficult to determine which of these variants corresponds to the “true” S. pinnata. We consider the specimens depicted in this page closely resemble the iconotype specimens presented by Ehrenberg (1843).


Original Description

F. pinnata, lineari-oblonga striis validis in 1/100 lin. 15, apicibus simpliciter rotundatis. Affinis striolatae et syricae. Icon!

  • Basionym
    Fragilaria pinnata
  • Author
    Ehrenb. 1843

Original Images

Staurosirella Pinnata  Iconotype
Staurosirella Pinnata  Original Description

EMAP Assessment

EMAP Distribution

Staurosirella Pinnata 10 Copy
Map 10

Response Plots

Staurosirella Pinnata Copy

Cite This Page

Morales, E. (2010). Staurosirella pinnata. In Diatoms of North America. Retrieved June 18, 2018, from https://diatoms.org/species/staurosirella_pinnata


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Staurosirella pinnata from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.