• Category
  • Length Range
    115.8-157.4 µm
  • Width Range
    27.4-34.4 µm
  • Striae in 10 µm
  • Synonyms
    Stauroneis nobilis f. alabamae (Heiden) A.Cleve 1953
  • Reported As
    Stauroneis nobilis (Patrick and Reimer 1966)



Valves are large and rhombic, with small specimens more elliptical lanceolate. Valve margins are slightly undulate near the apices. Apices are subcapitate.

Striae are parallel to slightly radiate near the stauros, becoming strongly radiate approximately halfway between the stauros and the apices and nearly parallel near the apices. In SEM images, it can be resolved that the striae immediately bordering the apex are convergent. Areolae are irregularly spaced throughout the center of the valve, but are evenly spaced near valve margins. A row of areolae borders the axial area.

The stauros is narrow and linear, and in some specimens constricted near the valve margins. Axial area is slightly expanded near the apices and broadens slightly as it meets the axial area.

The raphe is lateral. The proximal raphe ends are slightly expanded. The distal raphe ends are sickle shaped.

In SEM, it can be seen that the helictoglossa closely resembles the internal view of a rimoportula. The pseudoseptum is small occurring only as a small silica extension on one side of the raphe.

The differences between S. alabamae and S. alabamae var. angulata are currently unclear, and should be investigated when the Hustedt collection becomes accessible again.

Additional notes: In the original line drawing, S. alabamae var. angulata is depicted as being smaller than S. alabamae var. rostrata (=Stauroneis baconiana) and bears radiate striae bordering the stauros.

Stauroneis nobilis has historically been associated with S. alabamae. This association appears to have originated with Cleve's 1894 description of Stauroneis anceps var. nobilis, which was cited by Heiden in 1903. This association was perpetuated by Cleve-Euler (1953), then by Hustedt (1959), followed by Patrick and Reimer (1966), and most recently by Krammer and Lange-Bertalot (1986). However, as noted by Cleve in 1894, the original description clearly states that S. nobilis bears decussate striae. Further work should clarify the relationship of these large taxa.


Stauroneis alabamae co-occurs with many Pinnularia and Eunotia species. This diatom was also observed alongside a wide diversity of desmids such as Micrasterias, Spirotaenium, Cosmarium, Staurastrum, and Closterium.

Back Pond Jones Farm
Credit: Lane Allen
Location where Neidium iridis, Eunotia tecta and Stauroneis alabamae was collected in Bowie County, TX.

Original Description

  • Author
    Heiden 1903

Original Images

S alabamae orig image
S alabamae caption

Citations & Links


Cite This Page

Allen, L. (2023). Stauroneis alabamae. In Diatoms of North America. Retrieved December 02, 2023, from https://diatoms.org/species/stauroneis-alabamae


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Stauroneis alabamae 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.