• Category
  • Length Range
    23.3-111.2 µm
  • Width Range
    at the valve center: 11.4-16.7 µm
  • Striae in 10 µm
    7-11 in the valve center, 12-14 at the ends.
  • Reported As
    Eunotia praerupta var. bidens (Krammer and Lange-Bertalot 1991, p. 187, Fig. 148: 11-12)



Valves are weakly arcuate. The dorsal margins have two broadly rounded undulations. In larger specimens, apices are capitate and obtusely rounded. In smaller specimens, apices are subcapitate. The ends are 6.3-10.2 µm wide. Helictoglossae are visible on the ventral margin, at the apices. Small undulations are present on the ventral side. The raphe curves onto the ventral mantle toward the center valve, with proximal raphe ends positioned at the small ventral undulations. Transapical striae are nearly parallel, becoming curved near the ends. Shortened striae may be present in some specimens, near the dorsal margin. A narrow sternum is present near the ventral margin, near the apices. Areolae are fine and number 26-30 in 10 µm.

In North American specimens, the areolae are less dense than those documented in the original description (30-32 in 10 µm).


Due to the recent designation as a species by Lange-Bertalot (2011) and it's likely miss identification as E. praerupta var. bidens and E. bidens, the geographical distribution and ecological niche of E. superbidens is not yet well understood.

Burge (2014) found E. superbidens occurring in less than 30% relative abundance among the epiphyton and benthos of cypress-tupelo wetlands with: 22.2–27.4 C, 5.6–7.4 pH, specific conductivity 71.2–834.0 µS/cm, 8.1–321.0 NTU, DO 0.1–7.7 mg/L, NO3-N 0.01–0.3 mg/L, NO2-N <0.001– 0.1 mg/L, orthophosphate 0.02–2.08 mg/L, and TP 0.11–3.93 mg/L. Other common species were Eunotia bidens, E. bilunaris, E. formica, and E. metamonodon as well as species of Gomphonema, Navicula, Nitzschia, and Pinnularia.

Original Description

  • Author
    Lange-Bert. 2011
  • Length Range
    43-90 µm
  • Width
    14-19 µm
  • Striae in 10µm

Original Images

Eunotia superbidens orig illus
Eunotia superbidens SEM
Eusuperb Original Text

Cite This Page

Burge, D., Edlund, M. (2015). Eunotia superbidens. In Diatoms of North America. Retrieved June 19, 2024, from https://diatoms.org/species/eunotia_superbidens


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