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Staurophora amphioxys

(W.Greg.) D.G.Mann 1990      Category: Symmetrical biraphid
BASIONYM: Stauroneis amphioxys W.Greg. 1856

REPORTED AS: Stauroneis gregorii (Hustedt 1959, p.790, fig. 1135) 

Stauroneis vandevijveri


Staurophora brantii

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - January 2017
Length Range: 41-68 µm
Width Range: 12.3-17.5 µm
Striae in 10 µm: 13-16


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.

Original Description

Basionym: Stauroneis amphioxys
Author: W.Greg. 1856
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Bahls, L. (2017). Staurophora amphioxys. In Diatoms of the United States. Retrieved May 23, 2018, from

Species: Staurophora amphioxys

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


Gregory, W. (1856). Notice of some new species of British Fresh-water Diatomaceae. Quarterly Journal of Microscopical Science, new series, London 4:1-14, pl. I.

Hustedt, F. (1959). Die Kieselalgen Deutschlands, Osterreichs und der Schweiz, 2. Teil. In: Kryptogamen-Flora von Deutschlands, Osterreichs und der Schweiz, (Dr. L. Rabenhorst, ed.), Band VII(2). Reprint 1977, Otto Koeltz Science Publishers, Koenigstein, 845 pp.

Round, F.E., Crawford, R.M. and Mann, D.G. (1990). The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)


Autecology Discussion

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, Sheridan County, Montana: home of Staurophora amphioxys.

Credit/Source: Montana Department of Fish, Wildlife and Parks

Brush Lake, Sheridan County, Montana: home of Staurophora amphioxys.

Credit/Source: Doug Smith

Brush Lake, Sheridan County, Montana: home of Staurophora amphioxys.

Credit/Source: Jim Rea, Montana Department of Fish, Wildlife and Parks