• Category
  • Length Range
    8.9 – 16.0 µm
  • Width Range
    2.8-3.2 µm
  • Striae in 10 µm



The valve is barely asymmetric to the apical axis and narrowly lanceolate, becoming elliptical-lanceolate in smaller specimens. Apices are barely protracted in larger valves to broadly rounded in smaller valves. Striae are nearly parallel at the center of the valve, becoming slightly radiate toward the apices in larger valves. The axial area is narrow and linear. The central area is typically absent and small if present. The raphe is slightly arched toward the ventral margin


Very few records of Encyonopsis thumensis exist outside its type location in Lake Thumsee, Bavaria. Specimens were reported from a sediment core taken in Urpi Kocha Lagoon, Peru (Winsborough et al. 2012), but this identification could not be verified.

Encyonopsis thumensis is widespread in reference streams, those with minimal human impact, throughout Virginia and West Virginia (EPA 2008, National Streams and Rivers Survey).

Original Description

(12) Encyonopsis thumensis Krammer nov. spec. (Fig. 154: 13-15; 158: 16-22)

Valvae vix dorsiventrales, lineare, margine dorsali et ventrali paulo convexo, apicibus truncate rotundatis, 9,5-18μm longae, 3,5-4 μm latae. Area axialis angusta, area centralis nulla. Raphe filiformis, curvata ad marginis ventralibus, terminis proximalibus ad latus dorsale inclinatis, fissuris distalibus in latus ventrale deflexis. Striae in latere dorsali et ventrali modice radiantes, 23-26 in 10 μm, puncta 37-39 in 10 μm. Locus typicus: Thumsee apud Rechenhall. Leg. 8.1979. Typus: Praep. 347EIOK.

  • Author
    Krammer 1997
  • Length Range
    9.5-18 µm
  • Width
    3.5-4 µm
  • Striae in 10µm

Original Images

Encyonopsis thumensis orig illus 3
E Thumensis Orig Ill2 2
E Thumensis Orig Des 2

Cite This Page

Polaskey, M. (2016). Encyonopsis thumensis. In Diatoms of North America. Retrieved May 24, 2024, from https://diatoms.org/species/encyonopsis_thumensis


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