Encyonopsis dakotae

L.L.Bahls 2013      Category: Asymmetrical biraphid

Encyonopsis czarneckii


Encyonopsis descripta

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls - May 2013
Length Range: 24-32 µm
Width Range: 4.8-6.5 µm
Striae in 10 µm: 18-20 at the valve center, 21-23 at the apices


Valves are linear to linear-lanceolate and subtly triundulate. Valves are nearly symmetric with respect to the apical axis. Apices are capitate. The axial area is narrow and the central area is small and asymmetric, typically rounded on the dorsal side and squared on the ventral side. The raphe is lateral with proximal ends deflected to the dorsal side and ventral ends hooked toward the ventral side. Striae are radiate throughout and a bit more closely spaced near the apices. Areolae are very fine and difficult to resolve in LM.

Original Description

Author: L.L.Bahls 2013
Length Range: 24-32 µm
Width Range: 4.8-6.5 µm
Striae in 10 µm: 18-20 at valve center, 21-23 near the apices

Original Description

Valves linear-lanceolate and slightly dorsiventral. Apices capitate. Valve length 24–32 µm; valve width 4.8–6.5 µm. Axial area narrow, close to valve midline. Central area transverse, asymmetric, rounded on the dorsal side, defined by two or three irregularly shortened striae on the ventral side. Raphe weakly lateral, filiform near the proximal and distal ends. Proximal raphe ends weakly expanded, deflected dorsally. Distal raphe fissures hooked toward the ventral side. Striae radiate throughout, 18–20 in 10 µm at valve center, 21–23 in 10 µm near the apices.

Original Images

Cite This Page:
Bahls, L. (2013). Encyonopsis dakotae. In Diatoms of the United States. Retrieved April 25, 2018, from http://westerndiatoms.colorado.edu/taxa/species/encyonopsis_dakotae

Species: Encyonopsis dakotae

Contributor: Loren Bahls

Reviewer: Mark Edlund, Rex Lowe


Bahls, L. (2013). Encyonopsis from western North America: 31 species from Alberta, Idaho, Montana, Oregon, South Dakota, and Washington, including 17 species described as new. Northwest Diatoms, Volume 5. The Montana Diatom Collection, Helena, 46 pp.

Krammer, K. (1997). Die cymbelloiden Diatomeen. Eine Monographie der weltweit bekannten Taxa. Teil 2. Encyonema part., Encyonopsis and Cymbellopsis. Bibliotheca Diatomologica 37:1-469.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)


Autecology Discussion

Encyonopsis dakotae is known from the type locality, the Cheyenne River in Fall River County, South Dakota, and from Connelly Fen, a calcareous fen in Glacier County, Montana (photo below). Water quality data are not available for the type locality. The pH of Connelly Fen was 7.4 and specific conductance measured 1600 µS/cm.


Connelly Fen, Blackfeet Indian Reservation, Glacier County, Montana: home of Encyonopsis dakotae.

Credit/Source: Peter Lesica