• Category
  • Length Range
    52-70 µm
  • Width Range
    11.4-14.2 µm
  • Striae in 10 µm
  • Reported As
    Stauroneis (?nov.) spec. (Werum and Lange-Bertalot, 2004, Pl.50, Fig. 4)
    Stauroneis spec. cf. amphicephala Kützing (Lange-Bertalot and Genkal, 1999, Tafel 31, Fig. 8)
    Stauroneis (?nov.) spec. 2 Julma Olkky cf. anceps (Lange-Bertalot and Metzeltin, 1996, Tafel 32, Figs 5-6)



Valves are lanceolate with capitate apices. The axial area is narrow and nearly linear, widening slightly near the stauros. The stauros is shaped like a bow tie and is strongly expanded near the valve margins. External raphe fissures are moderately lateral. Proximal raphe ends are nearly straight. The proximal raphe pores are small and only slightly expanded. Striae are radiate throughout. Areolae are fine and number 22-26 in 10 µm.


Stauroneis ancepsfallax has been collected from several ponds and small lakes in the Northern Rockies. These waters have circumneutral pH (range 6.7-8.6) and low to moderate specific conductance (range 22-250 µS/cm). An unidentified taxon with similar features was reported from Siberia (Lange-Bertalot & Genkal 1999), from an oligo-dystrophic lake in Finland (Lange-Bertalot & Metzeltin 1996), and from springs in central Europe (Werum & Lange-Bertalot 2004).

Blakiston  Beaver  Pond  A
Credit: Barb Johnston, Parks Canada
Blakiston Beaver Pond A, Waterton Lakes National Park, Alberta: type locality for Stauroneis ancepsfallax.

Original Description

Valves lanceolate with capitate ends. Length 52-70 µm, width 11.4-14.2 µm. Axial area narrow, nearly linear, widening slightly near the central area. Central area shaped like a bow tie, strongly expanded toward valve margins. Raphe fissures moderately lateral, proximal endings nearly straight, weakly deflected to the secondary side. Central pores small, only slightly inflated. Striae radiate throughout, 17-23 in 10 µm. Striae puncta fine, 22-26 in 10 µm. For measurements, n = 14 valves.

  • Author
    L.L.Bahls 2010
  • Length Range
    52-70 µm
  • Width
    11.4-14.2 µm
  • Striae in 10µm

Original Images

Sancepsfallax Origimag
Sancepsfallax Origdesc

Cite This Page

Bahls, L. (2011). Stauroneis ancepsfallax. In Diatoms of North America. Retrieved July 23, 2018, from https://diatoms.org/species/stauroneis_ancepsfallax


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