• Category
  • Diameter
    33-66 µm



Valves are concentrically undulate with either concave or convex valve centers. Marginal spines are present, positioned at the end of every second to fifth hyaline costa (interfascicle). Areolae 12-18 in 10 µm and arranged in radiating striae separated by the interfascicles. Striae are uniseriate in the valve center, becoming multiseriate, up to 4 or 5 striae within a fascicle. Areolae appear round in high focus in LM. Internally, the areolae are closed by convex, domed cribra. Fascicles are closely spaced, separated by interfascicles. Central fultoportulae number 1-11, positioned in an irregular ring near the center of the valve; marginal fultoportulae are positioned between each marginal spine and the valve margin. Rimoportulae number 1-6, positioned near marginal spines, external expression a short tube that is shorter and thinner than a spine.


Stephanodiscus yellowstonensis evolved from S. niagarae in Yellowstone Lake, Wyoming (Theriot et al. 2006). It is endemic to the Yellowstone Lake basin, where it is dominant in the plankton community. Stephanodiscus yellowstonensis is considered to have evolved extremely rapidly, on the order of a few thousand years, as determined from examination of morphological features of Stephanodiscus niagarae and S. yellowstonensis in lake sediments.

Original Description

Valves disc-shaped, with diameters 33-66 µm observed. Central area convex or concave. Areolae in fascicles between radiating costae, 12-18 in 10 µm parallel to a stria. Foramina external; cribra internal. Spines 11 to 23, in a ring 3 to 5 µm from the margin; diameter at the base usually 1 to 1.7 µm. Labiate processes 1 to 6, in an irregular ring located just outside the ring of spines; diameter at the base usually 0.8 to 1.5 µm. Strutted processes 1 to 11, in an irregular ring in central area, one between each spine and the margin.

  • Author
    E.C.Ther. and Stoermer 1984
  • Length Range
    33-66 µm

Original Images

Orig Desc  Syellowsonensis

Cite This Page

Spaulding, S., Potapova, M. (2012). Stephanodiscus yellowstonensis. In Diatoms of North America. Retrieved May 24, 2024, from https://diatoms.org/species/stephanodiscus_yellowstonensis


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