Theriot and Stoermer 1984 Category: Centric
BASIONYM: Stephanodiscus yellowstonensis Theriot and Stoermer 1984
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.
Basionym: Stephanodiscus yellowstonensis
Author: Theriot and Stoermer 1984
Length Range: 33-66 µm
Striae in 10 µm:
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.
Cite This Page:
Spaulding, S., and Potapova, M. (2012). Stephanodiscus yellowstonensis. In Diatoms of the United States. Retrieved August 30, 2014, from http://westerndiatoms.colorado.edu/taxa/species/stephanodiscus_yellowstonensis
Species: Stephanodiscus yellowstonensis
Reviewer: Mark Edlund
Theriot, E.C., Fritz, S.C., Whitlock, C. and Conley, D.J. (2006). Late Quaternary rapid morphological evolution of an endemic diatom in Yellowstone Lake, Wyoming. Paleobiology 32: 38-54.
Theriot, E. and Stoermer, E.F. (1984). Principal component analysis of Stephanodiscus: Observations on two new species from the Stephanodiscus niagarae complex. Bacillaria 7: 37-53.
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.