• Category
  • Length Range
    40.8-67.6 µm
  • Width Range
    12.3-17.5 µm
  • Striae in 10 µm
  • Reported As
    Stauroneis gregorii (Hustedt 1959, p.790, fig. 1135)



Valves are lanceolate, with acutely pointed to broadly rounded apices. The valve face is highly arched in transapical section, merging gradually into the deep mantle. Raphe branches are straight and filiform. Proximal raphe ends are inconspicuous and bent slightly in the same direction. Terminal raphe fissures are curved and open toward the secondary side of the valve. The axial area is narrow and linear, widening slightly near the central area. The central area is a broad transverse fascia, sometimes shaped like a bow tie and wider towards the valve margins and sometimes nearly rectilinear. The central area is bordered by a few shortened striae on each side. Due to valve curvature, only the ends of the longest of these short striae are visible in valve view, making them appear to be more widely and more irregularly spaced than other striae. Striae are radiate, uniseriate and composed of small, round areolae.


The specimens of Staurophora amphioxys pictured on this website are from Brush Lake, a deep clear lake in the prairie pothole region of northeastern Montana (photos below). On the date of collection, Brush Lake had the following water quality characteristics: conductivity = 5760 µmhos/cm; pH = 9.30; total alkalinity = 1350 mg/L CaCO3; total hardness = 1168 mg/L equivalent CaCO3; Kjeldahl nitrogen = 1.3 mg/L; total phosphorus = 0.018 mg/L; dissolved oxygen = 7.50 mg/L; temperature = 18 C; CO3 = 1070 mg/l; SO4 = 2210 mg/L; Cl = 72.3 mg/L.

In Brush Lake, S. amphioxys is part of a remarkable diatom association that includes Scoliopleura peisonis, Surirella crumena, and other brackish-water species that are typical of coastal waters and inland waters of higher conductivity. Witkowski et al. (2000) report S. amphioxys as a “marine to brackish-water species widespread on European coasts of the Atlantic Ocean, found also in the Baltic Sea”. Hustedt (1959) reports it as a "mesohalobe, euryhaline salt water form, widely distributed and not rare in European coastal areas". The Brush Lake diatom flora may be a relict of the flora that populated the shallow inland sea that covered much of the Great Plains until about 55 million years ago.

Brush Lake  Brush Lake Sm
Credit: Montana Department of Fish, Wildlife & Parks
Brush Lake, Sheridan County, Montana: home of Surirella crumena.
Brush Lake  Doug Smith
Credit: Doug Smith
Brush Lake, Sheridan County, Montana: home of Surirella crumena.
Brush Lake  Jim Rea Mdfwp
Credit: Jim Rea, Montana Department of Fish, Wildlife & Parks
Brush Lake, Sheridan County, Montana: home of Surirella crumena.

Original Description

  • Basionym
    Stauroneis amphioxys
  • Author
    W.Greg. 1856

Original Images

Stauroneis Amphioxys Origimag
Stauroneis Amphioxys Origdesc

Cite This Page

Bahls, L. (2017). Staurophora amphioxys. In Diatoms of North America. Retrieved August 15, 2018, from https://diatoms.org/species/staurophora_amphioxys


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